diff --git a/Makefile.am b/Makefile.am
index 2b812d17..ffe7ca90 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -183,6 +183,17 @@ libavrdude_a_SOURCES = \
 	tpi.h \
 	usbasp.c \
 	usbasp.h \
+	serialupdi.c \
+	serialupdi.h \
+	updi_constants.h \
+	updi_link.c \
+	updi_link.h \
+	updi_state.c \
+	updi_state.h \
+	updi_readwrite.c \
+	updi_readwrite.h \
+	updi_nvm.c \
+	updi_nvm.h \
 	usbdevs.h \
 	usb_hidapi.c \
 	usb_libusb.c \
diff --git a/avrdude.conf.in b/avrdude.conf.in
index 5d1a7013..837c9f54 100644
--- a/avrdude.conf.in
+++ b/avrdude.conf.in
@@ -613,6 +613,13 @@ programmer
   reset  = 3; # TMS 7
 ;
 
+programmer
+  id    = "serialupdi";
+  desc  = "SerialUPDI";
+  type  = "serialupdi";
+  connection_type = serial;
+;
+
 programmer
   id    = "avrisp";
   desc  = "Atmel AVR ISP";
diff --git a/avrdude/serialupdi.c b/avrdude/serialupdi.c
new file mode 100644
index 00000000..0f4e70c1
--- /dev/null
+++ b/avrdude/serialupdi.c
@@ -0,0 +1,253 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Interface to the SerialUPDI programmer.
+ *
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+#include "ac_cfg.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "avrdude.h"
+#include "libavrdude.h"
+#include "serialupdi.h"
+#include "updi_link.h"
+#include "updi_state.h"
+#include "updi_readwrite.h"
+
+static void serialupdi_setup(PROGRAMMER * pgm)
+{
+  if ((pgm->cookie = malloc(sizeof(updi_state))) == 0) {
+    avrdude_message(MSG_INFO,
+	    "%s: serialupdi_setup(): Out of memory allocating private data\n",
+	    progname);
+    exit(1);
+  }
+  memset(pgm->cookie, 0, sizeof(updi_state));
+  updi_set_datalink_mode(pgm, UPDI_LINK_MODE_16BIT);
+}
+
+static void serialupdi_teardown(PROGRAMMER * pgm)
+{
+  free(pgm->cookie);
+}
+
+static int serialupdi_open(PROGRAMMER * pgm, char * port)
+{
+  strcpy(pgm->port, port);
+  return updi_link_open(pgm);
+}
+
+static int serialupdi_decode_sib(updi_sib_info * sib_info)
+{
+  char * str_ptr;
+
+  sib_info->sib_string[SIB_INFO_STRING_LENGTH]=0;
+  avrdude_message(MSG_DEBUG, "%s: Received SIB: [%s]\n", progname, sib_info->sib_string);
+  memset(sib_info->family_string, 0, SIB_INFO_FAMILY_LENGTH+1);
+  memset(sib_info->nvm_string, 0, SIB_INFO_NVM_LENGTH+1);
+  memset(sib_info->debug_string, 0, SIB_INFO_DEBUG_LENGTH+1);
+  memset(sib_info->pdi_string, 0, SIB_INFO_PDI_LENGTH+1);
+  memset(sib_info->pdi_string, 0, SIB_INFO_PDI_LENGTH+1);
+  memset(sib_info->extra_string, 0, SIB_INFO_EXTRA_LENGTH+1);
+
+  memcpy(sib_info->family_string, sib_info->sib_string, SIB_INFO_FAMILY_LENGTH);
+  memcpy(sib_info->nvm_string, sib_info->sib_string + 8, SIB_INFO_NVM_LENGTH);
+  memcpy(sib_info->debug_string, sib_info->sib_string + 11, SIB_INFO_DEBUG_LENGTH);
+  memcpy(sib_info->pdi_string, sib_info->sib_string + 15, SIB_INFO_PDI_LENGTH);
+  strcpy(sib_info->extra_string, (char *)sib_info->sib_string + 19);
+
+  str_ptr = strstr(sib_info->nvm_string, ":");
+  if (!str_ptr) {
+    avrdude_message(MSG_INFO, "%s: Incorrect format of NVM string\n", progname);
+    return -1;
+  }
+  sib_info->nvm_version = *(str_ptr+1);
+
+  str_ptr = strstr(sib_info->debug_string, ":");
+  if (!str_ptr) {
+    avrdude_message(MSG_INFO, "%s: Incorrect format of DEBUG string\n", progname);
+    return -1;
+  }
+  sib_info->debug_version = *(str_ptr+1);
+
+  avrdude_message(MSG_DEBUG, "%s: Device family ID: %s\n", progname, sib_info->family_string);
+  avrdude_message(MSG_DEBUG, "%s: NVM interface: %s\n", progname, sib_info->nvm_string);
+  avrdude_message(MSG_DEBUG, "%s: Debug interface: %s\n", progname, sib_info->debug_string);
+  avrdude_message(MSG_DEBUG, "%s: PDI oscillator: %s\n", progname, sib_info->pdi_string);
+  avrdude_message(MSG_DEBUG, "%s: Extra information: %s\n", progname, sib_info->extra_string);
+  switch (sib_info->nvm_version) {
+    case '0':
+      avrdude_message(MSG_INFO, "%s: NVM type 0: 16-bit, page oriented write\n", progname);
+      break;
+    case '2':
+      avrdude_message(MSG_INFO, "%s: NVM type 2: 24-bit, word oriented write\n", progname);
+      break;
+    case '3':
+      avrdude_message(MSG_INFO, "%s: NVM type 3: 16-bit, page oriented\n", progname);
+      break;
+    default:
+      avrdude_message(MSG_INFO, "%s: Unsupported NVM type: %c, please update software\n", progname, sib_info->nvm_version);
+      return -1;
+  }
+  return 0;
+}
+
+static void serialupdi_close(PROGRAMMER * pgm)
+{
+  updi_link_close(pgm);
+}
+
+static int serialupdi_initialize(PROGRAMMER * pgm, AVRPART * p)
+{
+  updi_sib_info * sib_info = updi_get_sib_info(pgm);
+
+  if (updi_link_init(pgm) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI link initialization failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_INFO, "%s: UPDI link initialization OK\n", progname);
+  if (updi_read_sib(pgm, sib_info->sib_string, 32) < 0) {
+    avrdude_message(MSG_INFO, "%s: Read SIB operation failed\n", progname);
+    return -1;
+  }
+  if (serialupdi_decode_sib(sib_info) < 0) {
+    avrdude_message(MSG_INFO, "%s: Decode SIB_INFO failed\n", progname);
+    return -1;
+  }
+  updi_set_nvm_mode(pgm, sib_info->nvm_version);
+  if (sib_info->nvm_version == '2') {
+    updi_set_datalink_mode(pgm, UPDI_LINK_MODE_24BIT);
+  } else {
+    updi_set_datalink_mode(pgm, UPDI_LINK_MODE_16BIT);
+  }
+  
+  return 0;
+}
+
+static void serialupdi_disable(PROGRAMMER * pgm)
+{
+  /* Do nothing. */
+
+  return;
+}
+
+static void serialupdi_enable(PROGRAMMER * pgm)
+{
+  /* Do nothing. */
+
+  return;
+}
+
+static void serialupdi_display(PROGRAMMER * pgm, const char * p)
+{
+  return;
+}
+
+static int serialupdi_cmd(PROGRAMMER * pgm, const unsigned char * cmd,
+                          unsigned char * res)
+{
+  avrdude_message(MSG_INFO, "%s: error: cmd %s[%s] not implemented yet\n",
+    	    progname, cmd, res);
+  return -1;
+}
+
+static int serialupdi_program_enable(PROGRAMMER * pgm, AVRPART * p)
+{
+  avrdude_message(MSG_INFO, "%s: error: program enable not implemented yet\n",
+    	    progname);
+  return -1;
+}
+
+static int serialupdi_chip_erase(PROGRAMMER * pgm, AVRPART * p)
+{
+  avrdude_message(MSG_INFO, "%s: error: chip erase not implemented yet\n",
+    	    progname);
+  return -1;
+}
+
+static int serialupdi_read_byte(PROGRAMMER * pgm, AVRPART * p, AVRMEM * mem, 
+                                unsigned long addr, unsigned char * value)
+{
+//  avrdude_message(MSG_INFO, "%s: error: read byte not implemented yet\n",
+//    	            progname);
+  return updi_read_byte(pgm, mem->offset + addr, value);
+//  return -1;
+}
+
+static int serialupdi_paged_load(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
+                                 unsigned int page_size,
+                                 unsigned int addr, unsigned int n_bytes)
+{
+  avrdude_message(MSG_INFO, "%s: error: paged load not implemented yet\n",
+    	    progname);
+  return -1;
+}
+
+static int serialupdi_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
+                                  unsigned int page_size,
+                                  unsigned int addr, unsigned int n_bytes)
+{
+  avrdude_message(MSG_INFO, "%s: error: paged write not implemented yet\n",
+    	    progname);
+  return -1;
+}
+
+void serialupdi_initpgm(PROGRAMMER * pgm)
+{
+  strcpy(pgm->type, "serialupdi");
+
+  /*
+   * mandatory functions
+   */
+
+  pgm->initialize     = serialupdi_initialize;
+  pgm->display        = serialupdi_display;
+  pgm->enable         = serialupdi_enable;
+  pgm->disable        = serialupdi_disable;
+  pgm->program_enable = serialupdi_program_enable;
+  pgm->chip_erase     = serialupdi_chip_erase;
+  pgm->cmd            = serialupdi_cmd;
+  pgm->open           = serialupdi_open;
+  pgm->close          = serialupdi_close;
+  pgm->read_byte      = serialupdi_read_byte;
+  pgm->write_byte     = avr_write_byte_default;
+
+  /*
+   * optional functions
+   */
+
+  pgm->paged_write    = serialupdi_paged_write;
+  pgm->paged_load     = serialupdi_paged_load;
+  pgm->setup          = serialupdi_setup;
+  pgm->teardown       = serialupdi_teardown;
+
+}
+
+const char serialupdi_desc[] = "Driver for SerialUPDI programmers";
diff --git a/avrdude/serialupdi.h b/avrdude/serialupdi.h
new file mode 100644
index 00000000..ff7270d5
--- /dev/null
+++ b/avrdude/serialupdi.h
@@ -0,0 +1,43 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef serialupdi_h
+#define serialupdi_h
+
+#include "libavrdude.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern const char serialupdi_desc[];
+void serialupdi_initpgm (PROGRAMMER * pgm);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* serialupdi_h */
diff --git a/avrdude/updi_constants.h b/avrdude/updi_constants.h
new file mode 100644
index 00000000..ff8a446f
--- /dev/null
+++ b/avrdude/updi_constants.h
@@ -0,0 +1,156 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef updi_constants_h
+#define updi_constants_h
+
+#define UPDI_BREAK       0x00
+
+#define UPDI_LDS         0x00
+#define UPDI_STS         0x40
+#define UPDI_LD          0x20
+#define UPDI_ST          0x60
+#define UPDI_LDCS        0x80
+#define UPDI_STCS        0xC0
+#define UPDI_REPEAT      0xA0
+#define UPDI_KEY         0xE0
+
+#define UPDI_PTR         0x00
+#define UPDI_PTR_INC     0x04
+#define UPDI_PTR_ADDRESS 0x08
+
+#define UPDI_ADDRESS_8   0x00
+#define UPDI_ADDRESS_16  0x04
+#define UPDI_ADDRESS_24  0x08
+
+#define UPDI_DATA_8      0x00
+#define UPDI_DATA_16     0x01
+#define UPDI_DATA_24     0x02
+
+#define UPDI_KEY_SIB     0x04
+#define UPDI_KEY_KEY     0x00
+
+#define UPDI_KEY_64      0x00
+#define UPDI_KEY_128     0x01
+#define UPDI_KEY_256     0x02
+
+#define UPDI_SIB_8BYTES  UPDI_KEY_64
+#define UPDI_SIB_16BYTES UPDI_KEY_128
+#define UPDI_SIB_32BYTES UPDI_KEY_256
+
+#define UPDI_REPEAT_BYTE 0x00
+#define UPDI_REPEAT_WORD 0x01
+
+#define UPDI_PHY_SYNC    0x55
+#define UPDI_PHY_ACK     0x40
+
+#define UPDI_MAX_REPEAT_SIZE (0xFF+1) // Repeat counter of 1-byte, with off-by-one counting
+
+//# CS and ASI Register Address map
+#define UPDI_CS_STATUSA     0x00
+#define UPDI_CS_STATUSB     0x01
+#define UPDI_CS_CTRLA       0x02
+#define UPDI_CS_CTRLB       0x03
+#define UPDI_ASI_KEY_STATUS 0x07
+#define UPDI_ASI_RESET_REQ  0x08
+#define UPDI_ASI_CTRLA      0x09
+#define UPDI_ASI_SYS_CTRLA  0x0A
+#define UPDI_ASI_SYS_STATUS 0x0B
+#define UPDI_ASI_CRC_STATUS 0x0C
+
+#define UPDI_CTRLA_IBDLY_BIT    7
+#define UPDI_CTRLB_CCDETDIS_BIT 3
+#define UPDI_CTRLB_UPDIDIS_BIT  2
+
+#define UPDI_KEY_NVM       "NVMProg "
+#define UPDI_KEY_CHIPERASE "NVMErase"
+#define UPDI_KEY_UROW      "NVMUs&te"
+
+#define UPDI_ASI_STATUSA_REVID 4
+#define UPDI_ASI_STATUSB_PESIG 0
+
+#define UPDI_ASI_KEY_STATUS_CHIPERASE  3
+#define UPDI_ASI_KEY_STATUS_NVMPROG    4
+#define UPDI_ASI_KEY_STATUS_UROWWRITE  5
+
+#define UPDI_ASI_SYS_STATUS_RSTSYS     5
+#define UPDI_ASI_SYS_STATUS_INSLEEP    4
+#define UPDI_ASI_SYS_STATUS_NVMPROG    3
+#define UPDI_ASI_SYS_STATUS_UROWPROG   2
+#define UPDI_ASI_SYS_STATUS_LOCKSTATUS 0
+
+#define UPDI_ASI_SYS_CTRLA_UROW_FINAL  1
+
+#define UPDI_RESET_REQ_VALUE  0x59
+
+// FLASH CONTROLLER
+#define UPDI_NVMCTRL_CTRLA    0x00
+#define UPDI_NVMCTRL_CTRLB    0x01
+#define UPDI_NVMCTRL_STATUS   0x02
+#define UPDI_NVMCTRL_INTCTRL  0x03
+#define UPDI_NVMCTRL_INTFLAGS 0x04
+#define UPDI_NVMCTRL_DATAL    0x06
+#define UPDI_NVMCTRL_DATAH    0x07
+#define UPDI_NVMCTRL_ADDRL    0x08
+#define UPDI_NVMCTRL_ADDRH    0x09
+
+// NVMCTRL v0 CTRLA
+#define UPDI_V0_NVMCTRL_CTRLA_NOP              0x00
+#define UPDI_V0_NVMCTRL_CTRLA_WRITE_PAGE       0x01
+#define UPDI_V0_NVMCTRL_CTRLA_ERASE_PAGE       0x02
+#define UPDI_V0_NVMCTRL_CTRLA_ERASE_WRITE_PAGE 0x03
+#define UPDI_V0_NVMCTRL_CTRLA_PAGE_BUFFER_CLR  0x04
+#define UPDI_V0_NVMCTRL_CTRLA_CHIP_ERASE       0x05
+#define UPDI_V0_NVMCTRL_CTRLA_ERASE_EEPROM     0x06
+#define UPDI_V0_NVMCTRL_CTRLA_WRITE_FUSE       0x07
+
+// NVMCTRL v2 CTRLA
+#define UPDI_V2_NVMCTRL_CTRLA_NOCMD              0x00
+#define UPDI_V2_NVMCTRL_CTRLA_FLASH_WRITE        0x02
+#define UPDI_V2_NVMCTRL_CTRLA_FLASH_PAGE_ERASE   0x08
+#define UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE_WRITE 0x13
+#define UPDI_V2_NVMCTRL_CTRLA_CHIP_ERASE         0x20
+#define UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE       0x30
+
+// NVMCTRL v3 CTRLA
+#define UPDI_V3_NVMCTRL_CTRLA_NOCMD                    0x00
+#define UPDI_V3_NVMCTRL_CTRLA_NOP                      0x01
+#define UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_WRITE         0x04
+#define UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_ERASE_WRITE   0x05
+#define UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_ERASE         0x08
+#define UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_BUFFER_CLEAR  0x0F
+#define UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_WRITE        0x14
+#define UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_ERASE_WRITE  0x15
+#define UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_ERASE        0x17
+#define UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_BUFFER_CLEAR 0x1F
+#define UPDI_V3_NVMCTRL_CTRLA_CHIP_ERASE               0x20
+#define UPDI_V3_NVMCTRL_CTRLA_EEPROM_ERASE             0x30
+
+#define UPDI_NVM_STATUS_WRITE_ERROR 2
+#define UPDI_NVM_STATUS_EEPROM_BUSY 1
+#define UPDI_NVM_STATUS_FLASH_BUSY  0
+
+#endif /* updi_constants_h */
diff --git a/avrdude/updi_link.c b/avrdude/updi_link.c
new file mode 100644
index 00000000..33c3da1d
--- /dev/null
+++ b/avrdude/updi_link.c
@@ -0,0 +1,825 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#include "ac_cfg.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "avrdude.h"
+#include "libavrdude.h"
+#include "updi_link.h"
+#include "updi_constants.h"
+#include "updi_state.h"
+
+#include <sys/time.h>
+
+void msleep(int tms)
+{
+    struct timeval tv;
+    tv.tv_sec  = tms / 1000;
+    tv.tv_usec = (tms % 1000) * 1000;
+    select (0, NULL, NULL, NULL, &tv);
+}
+
+static int updi_physical_open(PROGRAMMER* pgm, int baudrate, unsigned long cflags)
+{
+  serial_recv_timeout = 100;
+  union pinfo pinfo;
+
+  pinfo.serialinfo.baud = baudrate;
+  pinfo.serialinfo.cflags = cflags;
+
+  avrdude_message(MSG_DEBUG, "%s: Opening serial port...\n", progname);
+
+  if (serial_open(pgm->port, pinfo, &pgm->fd)==-1) {
+
+    avrdude_message(MSG_INFO, "%s: Serial port open failed!\n", progname);
+    return -1;
+  }
+
+  /*
+   * drain any extraneous input
+   */
+  serial_drain(&pgm->fd, 0);
+
+  return 0;
+}
+
+static void updi_physical_close(PROGRAMMER* pgm)
+{
+  serial_close(&pgm->fd);
+  pgm->fd.ifd = -1;
+}
+
+static int updi_physical_send(PROGRAMMER * pgm, unsigned char * buf, size_t len)
+{
+  size_t i;
+  int rv;
+
+  avrdude_message(MSG_DEBUG, "%s: Sending %lu bytes [", progname, len);
+  for (i=0; i<len; i++) {
+    avrdude_message(MSG_DEBUG, "0x%02x", buf[i]);
+    if (i<len-1) {
+      avrdude_message(MSG_DEBUG, ", ");
+    }
+  }
+  avrdude_message(MSG_DEBUG, "]\n");
+
+  rv = serial_send(&pgm->fd, buf, len);
+  serial_recv(&pgm->fd, buf, len);
+  return rv;
+}
+
+static int updi_physical_recv(PROGRAMMER * pgm, unsigned char * buf, size_t len)
+{
+  size_t i;
+  int rv;
+
+  rv = serial_recv(&pgm->fd, buf, len);
+  if (rv < 0) {
+    avrdude_message(MSG_DEBUG,
+      "%s: serialupdi_recv(): programmer is not responding\n",
+      progname);
+    return -1;
+  }
+
+  avrdude_message(MSG_DEBUG, "%s: Received %lu bytes [", progname, len);
+  for (i=0; i<len; i++) {
+    avrdude_message(MSG_DEBUG, "0x%02x", buf[i]);
+    if (i<len-1) {
+      avrdude_message(MSG_DEBUG, ", ");
+    }
+  }
+  avrdude_message(MSG_DEBUG, "]\n");
+
+  return len;
+}
+
+static int updi_physical_send_double_break(PROGRAMMER * pgm)
+{
+  unsigned char buffer[1];
+
+  avrdude_message(MSG_DEBUG, "%s: Sending double break\n", progname);
+
+  updi_physical_close(pgm);
+
+  if (updi_physical_open(pgm, 300, SERIAL_8E1)==-1) {
+
+    return -1;
+  }
+
+  buffer[0] = UPDI_BREAK;
+
+  serial_send(&pgm->fd, buffer, 1);
+  serial_recv(&pgm->fd, buffer, 1);
+
+  msleep(100);
+
+  buffer[0] = UPDI_BREAK;
+
+  serial_send(&pgm->fd, buffer, 1);
+  serial_recv(&pgm->fd, buffer, 1);
+
+  updi_physical_close(pgm);
+
+  return updi_physical_open(pgm, pgm->baudrate? pgm->baudrate: 115200, SERIAL_8E2);
+}
+
+int updi_physical_sib(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size)
+{
+/*
+    def sib(self):
+        """
+        System information block is just a string coming back from a SIB command
+        """
+        self.send([
+            constants.UPDI_PHY_SYNC,
+            constants.UPDI_KEY | constants.UPDI_KEY_SIB | constants.UPDI_SIB_32BYTES])
+        return self.ser.readline()
+*/
+  unsigned char send_buffer[2];
+
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_KEY | UPDI_KEY_SIB | UPDI_SIB_32BYTES;
+
+  if (updi_physical_send(pgm, send_buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: SIB request send failed\n", progname);
+    return -1;
+  }
+
+  return updi_physical_recv(pgm, buffer, size);
+}
+
+int updi_link_open(PROGRAMMER * pgm) 
+{
+  return updi_physical_open(pgm, pgm->baudrate? pgm->baudrate: 115200, 
+                            (SERIAL_CS8 | SERIAL_CSTOPB | SERIAL_CREAD | SERIAL_PARENB | SERIAL_CLOCAL));
+}
+
+void updi_link_close(PROGRAMMER * pgm)
+{
+  updi_physical_close(pgm);
+}
+
+static int updi_link_init_session_parameters(PROGRAMMER * pgm) 
+{
+/*
+    def _init_session_parameters(self):
+        """
+        Set the inter-byte delay bit and disable collision detection
+        """
+        self.stcs(constants.UPDI_CS_CTRLB, 1 << constants.UPDI_CTRLB_CCDETDIS_BIT)
+        self.stcs(constants.UPDI_CS_CTRLA, 1 << constants.UPDI_CTRLA_IBDLY_BIT)
+*/
+  if (updi_link_stcs(pgm, UPDI_CS_CTRLB, 1 << UPDI_CTRLB_CCDETDIS_BIT) < 0) {
+    return -1;
+  }
+
+  if (updi_link_stcs(pgm, UPDI_CS_CTRLA, 1 << UPDI_CTRLA_IBDLY_BIT) < 0) {
+    return -1;
+  }
+
+  return 0;
+}
+
+static int updi_link_check(PROGRAMMER * pgm)
+{
+/*
+    def _check_datalink(self):
+        """
+        Check UPDI by loading CS STATUSA
+        """
+        try:
+            if self.ldcs(constants.UPDI_CS_STATUSA) != 0:
+                self.logger.info("UPDI init OK")
+                return True
+        except PymcuprogError:
+            self.logger.warning("Check failed")
+            return False
+        self.logger.info("UPDI not OK - reinitialisation required")
+        return False
+*/
+  int result;
+  uint8_t value;
+  result = updi_link_ldcs(pgm, UPDI_CS_STATUSA, &value);
+  if (result < 0) {
+    avrdude_message(MSG_DEBUG, "%s: Check failed\n", progname);
+    return -1;
+  } else {
+    if (value > 0) {
+      avrdude_message(MSG_DEBUG, "%s: UDPI init OK\n", progname);
+      return 0;
+    } else {
+      avrdude_message(MSG_DEBUG, "%s: UDPI not OK - reinitialisation required\n", progname);
+      return -1;
+    }
+  }
+}
+
+
+int updi_link_init(PROGRAMMER * pgm)
+{
+/*
+    def init_datalink(self):
+        """
+        Init DL layer
+        """
+        self._init_session_parameters()
+        # Check
+        if not self._check_datalink():
+            # Send double break if all is not well, and re-check
+            self.updi_phy.send_double_break()
+            self._init_session_parameters()
+            if not self._check_datalink():
+                raise PymcuprogError("UPDI initialisation failed")
+*/
+  if (updi_link_init_session_parameters(pgm) < 0) {
+    avrdude_message(MSG_INFO, "%s: Session initialisation failed\n", progname);
+    return -1;
+  }
+
+  if (updi_link_check(pgm) < 0) {
+    avrdude_message(MSG_DEBUG, "%s: Datalink not active, resetting...\n", progname);
+    if (updi_physical_send_double_break(pgm) < 0) {
+      avrdude_message(MSG_INFO, "%s: Datalink initialisation failed\n", progname);
+      return -1;
+    }
+    if (updi_link_init_session_parameters(pgm) < 0) {
+      avrdude_message(MSG_INFO, "%s: Session initialisation failed\n", progname);
+      return -1;
+    }
+    if (updi_link_check(pgm) < 0) {
+      avrdude_message(MSG_INFO, "%s: Restoring datalink failed\n", progname);
+      return -1;
+    }
+  }
+  return 0;
+}
+
+int updi_link_ldcs(PROGRAMMER * pgm, uint8_t address, uint8_t * value) 
+{
+/*
+    def ldcs(self, address):
+        """
+        Load data from Control/Status space
+
+        :param address: address to load
+        """
+        self.logger.debug("LDCS from 0x%02X", address)
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_LDCS | (address & 0x0F)])
+        response = self.updi_phy.receive(self.LDCS_RESPONSE_BYTES)
+        numbytes_received = len(response)
+        if numbytes_received != self.LDCS_RESPONSE_BYTES:
+            raise PymcuprogError("Unexpected number of bytes in response: "
+                                 "{} byte(s) expected {} byte(s)".format(numbytes_received, self.LDCS_RESPONSE_BYTES))
+
+        return response[0]
+*/
+  unsigned char buffer[2];
+  int result;
+  avrdude_message(MSG_DEBUG, "%s: LDCS from 0x%02X\n", progname, address);
+  buffer[0]=UPDI_PHY_SYNC;
+  buffer[1]=UPDI_LDCS | (address & 0x0F);
+  if (updi_physical_send(pgm, buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: LDCS send operation failed\n", progname);
+    return -1;
+  }
+  result = updi_physical_recv(pgm, buffer, 1);
+  if (result != 1) {
+    if (result >= 0) {
+      avrdude_message(MSG_INFO, "%s: Incorrect response size, received %d instead of %d bytes\n", progname, result, 1);
+    }
+    return -1;
+  }
+  * value = buffer[0];
+  return 0;
+}
+
+int updi_link_stcs(PROGRAMMER * pgm, uint8_t address, uint8_t value)
+{
+/*
+    def stcs(self, address, value):
+        """
+        Store a value to Control/Status space
+
+        :param address: address to store to
+        :param value: value to write
+        """
+        self.logger.debug("STCS to 0x%02X", address)
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_STCS | (address & 0x0F), value])
+*/
+  unsigned char buffer[3];
+  avrdude_message(MSG_DEBUG, "%s: STCS 0x%02X to address 0x%02X\n", progname, value, address);
+  buffer[0] = UPDI_PHY_SYNC;
+  buffer[1] = UPDI_STCS | (address & 0x0F);
+  buffer[2] = value;
+  return updi_physical_send(pgm, buffer, 3);
+}
+
+int updi_link_ld_ptr_inc(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size)
+{
+/*
+    def ld_ptr_inc(self, size):
+        """
+        Loads a number of bytes from the pointer location with pointer post-increment
+ 
+        :param size: number of bytes to load
+        :return: values read
+        """
+        self.logger.debug("LD8 from ptr++")
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_LD | constants.UPDI_PTR_INC |
+                            constants.UPDI_DATA_8])
+        return self.updi_phy.receive(size)
+*/
+  unsigned char send_buffer[2];
+  avrdude_message(MSG_DEBUG, "%s: LD8 from ptr++\n", progname);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_LD | UPDI_PTR_INC | UPDI_DATA_8;
+  if (updi_physical_send(pgm, send_buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD_PTR_INC send operation failed\n", progname);
+    return -1;
+  }
+  return updi_physical_recv(pgm, buffer, size);
+}
+
+int updi_link_ld_ptr_inc16(PROGRAMMER * pgm, unsigned char * buffer, uint16_t words)
+{
+/*
+    def ld_ptr_inc16(self, words):
+        """
+        Load a 16-bit word value from the pointer location with pointer post-increment
+
+        :param words: number of words to load
+        :return: values read
+        """
+        self.logger.debug("LD16 from ptr++")
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_LD | constants.UPDI_PTR_INC |
+                            constants.UPDI_DATA_16])
+        return self.updi_phy.receive(words << 1)
+*/
+  unsigned char send_buffer[2];
+  avrdude_message(MSG_DEBUG, "%s: LD16 from ptr++\n", progname);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_LD | UPDI_PTR_INC | UPDI_DATA_16;
+  if (updi_physical_send(pgm, send_buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD_PTR_INC send operation failed\n", progname);
+    return -1;
+  }
+  return updi_physical_recv(pgm, buffer, words << 2);
+}
+
+int updi_link_st_ptr_inc(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size)
+{
+/*
+    def st_ptr_inc(self, data):
+        """
+        Store data to the pointer location with pointer post-increment
+
+        :param data: data to store
+        """
+        self.logger.debug("ST8 to *ptr++")
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_ST | constants.UPDI_PTR_INC | constants.UPDI_DATA_8,
+                            data[0]])
+        response = self.updi_phy.receive(1)
+
+        if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+            raise PymcuprogError("ACK error with st_ptr_inc")
+
+        num = 1
+        while num < len(data):
+            self.updi_phy.send([data[num]])
+            response = self.updi_phy.receive(1)
+
+            if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+                raise PymcuprogError("Error with st_ptr_inc")
+            num += 1
+*/
+  unsigned char send_buffer[3];
+  unsigned char recv_buffer[1];
+  int response;
+  int num = 1;
+  avrdude_message(MSG_DEBUG, "%s: ST8 to *ptr++\n", progname);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_ST | UPDI_PTR_INC | UPDI_DATA_8;
+  send_buffer[2] = buffer[0];
+  if (updi_physical_send(pgm, send_buffer, 3) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR_INC send operation failed\n", progname);
+    return -1;
+  }
+
+  response = updi_physical_recv(pgm, recv_buffer, 1);
+
+  if (response != 1 || recv_buffer[0] != UPDI_PHY_ACK) {
+    avrdude_message(MSG_INFO, "%s: ACK was expected but not received\n", progname);
+    return -1;
+  }
+
+  while (num < size) {
+    send_buffer[0]=buffer[num];
+    if (updi_physical_send(pgm, send_buffer, 1) < 0) {
+      avrdude_message(MSG_INFO, "%s: ST_PTR_INC data send operation failed\n", progname);
+      return -1;
+    }
+    response = updi_physical_recv(pgm, recv_buffer, 1);
+
+    if (response != 1 || recv_buffer[0] != UPDI_PHY_ACK) {
+      avrdude_message(MSG_INFO, "%s: Data ACK was expected but not received\n", progname);
+      return -1;
+    }
+    num++;
+  }
+
+  return 0;
+}
+
+int updi_link_st_ptr_inc16(PROGRAMMER * pgm, unsigned char * buffer, uint16_t words)
+{
+/*
+    def st_ptr_inc16(self, data):
+        """
+        Store a 16-bit word value to the pointer location with pointer post-increment
+
+        :param data: data to store
+        """
+        self.logger.debug("ST16 to *ptr++")
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_ST | constants.UPDI_PTR_INC |
+                            constants.UPDI_DATA_16, data[0], data[1]])
+        response = self.updi_phy.receive(1)
+
+        if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+            raise PymcuprogError("ACK error with st_ptr_inc16")
+
+        num = 2
+        while num < len(data):
+            self.updi_phy.send([data[num], data[num + 1]])
+            response = self.updi_phy.receive(1)
+
+            if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+                raise PymcuprogError("Error with st_ptr_inc16")
+            num += 2
+*/
+  unsigned char send_buffer[4];
+  unsigned char recv_buffer[1];
+  int response;
+  int num = 2;
+  avrdude_message(MSG_DEBUG, "%s: ST16 to *ptr++\n", progname);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_ST | UPDI_PTR_INC | UPDI_DATA_16;
+  send_buffer[2] = buffer[0];
+  send_buffer[3] = buffer[1];
+  if (updi_physical_send(pgm, send_buffer, 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR_INC16 send operation failed\n", progname);
+    return -1;
+  }
+
+  response = updi_physical_recv(pgm, recv_buffer, 1);
+
+  if (response != 1 || recv_buffer[0] != UPDI_PHY_ACK) {
+    avrdude_message(MSG_INFO, "%s: ACK was expected but not received\n", progname);
+    return -1;
+  }
+
+  while (num < words) {
+    send_buffer[0]=buffer[num];
+    send_buffer[1]=buffer[num+1];
+    if (updi_physical_send(pgm, send_buffer, 2) < 0) {
+      avrdude_message(MSG_INFO, "%s: ST_PTR_INC data send operation failed\n", progname);
+      return -1;
+    }
+    response = updi_physical_recv(pgm, recv_buffer, 1);
+
+    if (response != 1 || recv_buffer[0] != UPDI_PHY_ACK) {
+      avrdude_message(MSG_INFO, "%s: Data ACK was expected but not received\n", progname);
+      return -1;
+    }
+    num+=2;
+  }
+
+  return 0;
+}
+
+int updi_link_repeat(PROGRAMMER * pgm, uint16_t repeats)
+{
+/*
+    def repeat(self, repeats):
+        """
+        Store a value to the repeat counter
+
+        :param repeats: number of repeats requested
+        """
+        self.logger.debug("Repeat %d", repeats)
+        if (repeats - 1) > constants.UPDI_MAX_REPEAT_SIZE:
+            self.logger.error("Invalid repeat count of %d", repeats)
+            raise Exception("Invalid repeat count!")
+        repeats -= 1
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_REPEAT | constants.UPDI_REPEAT_BYTE,
+                            repeats & 0xFF])
+*/
+  unsigned char buffer[3];
+  avrdude_message(MSG_DEBUG, "%s: Repeat %d\n", progname, repeats);
+  if ((repeats - 1) > UPDI_MAX_REPEAT_SIZE) {
+    avrdude_message(MSG_INFO, "%s: Invalid repeat count of %d\n", progname, repeats);
+    return -1;
+  }
+  repeats-=1;
+  buffer[0] = UPDI_PHY_SYNC;
+  buffer[1] = UPDI_REPEAT | UPDI_REPEAT_BYTE;
+  buffer[2] = repeats & 0xFF;
+  return updi_physical_send(pgm, buffer, 3);
+}
+
+int updi_link_read_sib(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size)
+{
+/*
+    def read_sib(self):
+        """
+        Read the SIB
+        """
+        return self.updi_phy.sib()
+*/
+  return updi_physical_sib(pgm, buffer, size);
+}
+
+int updi_link_key(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size_type, uint16_t size)
+{
+/*
+    def key(self, size, key):
+        """
+        Write a key
+ 
+        :param size: size of key (0=64B, 1=128B, 2=256B)
+        :param key: key value
+        """
+        self.logger.debug("Writing key")
+        if len(key) != 8 << size:
+            raise PymcuprogError("Invalid KEY length!")
+        self.updi_phy.send([constants.UPDI_PHY_SYNC, constants.UPDI_KEY | constants.UPDI_KEY_KEY | size])
+        self.updi_phy.send(list(reversed(list(key))))
+*/
+  unsigned char send_buffer[2];
+  unsigned char reversed_key[256];
+  int index;
+  avrdude_message(MSG_DEBUG, "%s: UPDI writing key\n", progname);
+  if (size != (8 << size_type)) {
+    avrdude_message(MSG_INFO, "%s: Invalid key length\n", progname);
+    return -1;
+  }
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_KEY | UPDI_KEY_KEY | size_type;
+  if (updi_physical_send(pgm, send_buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI key send message failed\n", progname);
+    return -1;
+  }
+  /* reverse key contents */
+  for (index=0; index<size; index++) {
+    reversed_key[index] = buffer[size-index-1];
+  }
+  return updi_physical_send(pgm, reversed_key, size);
+}
+
+int updi_link_ld(PROGRAMMER * pgm, uint32_t address, uint8_t * value)
+{
+/*
+    def ld(self, address):
+        """
+        Load a single byte direct from a 24-bit address
+
+        :param address: address to load from
+        :return: value read
+        """
+        self.logger.info("LD from 0x{0:06X}".format(address))
+        self.updi_phy.send(
+            [constants.UPDI_PHY_SYNC, constants.UPDI_LDS | constants.UPDI_ADDRESS_24 | constants.UPDI_DATA_8,
+             address & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF])
+        return self.updi_phy.receive(1)[0]
+*/
+  unsigned char send_buffer[5];
+  unsigned char recv_buffer[1];
+  avrdude_message(MSG_DEBUG, "%s: LD from 0x%06X\n", progname, address);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_LDS | UPDI_DATA_8 | (updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? UPDI_ADDRESS_24 : UPDI_ADDRESS_16);
+  send_buffer[2] = address & 0xFF;
+  send_buffer[3] = (address >> 8) & 0xFF;
+  send_buffer[4] = (address >> 16) & 0xFF;
+  if (updi_physical_send(pgm, send_buffer, updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? 5 : 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD operation send failed\n", progname);
+    return -1;
+  }
+  if (updi_physical_recv(pgm, recv_buffer, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD operation recv failed\n", progname);
+    return -1;
+  }
+  * value = recv_buffer[0];
+  return 0;
+}
+
+int updi_link_ld16(PROGRAMMER * pgm, uint32_t address, uint16_t * value)
+{
+/*
+    def ld16(self, address):
+        """
+        Load a 16-bit word directly from a 24-bit address
+
+        :param address: address to load from
+        :return: values read
+        """
+        self.logger.info("LD from 0x{0:06X}".format(address))
+        self.updi_phy.send(
+            [constants.UPDI_PHY_SYNC, constants.UPDI_LDS | constants.UPDI_ADDRESS_24 | constants.UPDI_DATA_16,
+             address & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF])
+        return self.updi_phy.receive(2)
+*/
+  unsigned char send_buffer[5];
+  unsigned char recv_buffer[2];
+  avrdude_message(MSG_DEBUG, "%s: LD16 from 0x%06X\n", progname, address);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_LDS | UPDI_DATA_16 | (updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? UPDI_ADDRESS_24 : UPDI_ADDRESS_16);
+  send_buffer[2] = address & 0xFF;
+  send_buffer[3] = (address >> 8) & 0xFF;
+  send_buffer[4] = (address >> 16) & 0xFF;
+  if (updi_physical_send(pgm, send_buffer, updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? 5 : 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD16 operation send failed\n", progname);
+    return -1;
+  }
+  if (updi_physical_recv(pgm, recv_buffer, 2) < 0) {
+    avrdude_message(MSG_INFO, "%s: LD16 operation recv failed\n", progname);
+    return -1;
+  }
+  * value = (recv_buffer[0] << 8 | recv_buffer[1]);
+  return 0;
+}
+
+static int updi_link_st_data_phase(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size)
+{
+/*
+    def _st_data_phase(self, values):
+        """
+        Performs data phase of transaction:
+        * receive ACK
+        * send data
+
+        :param values: bytearray of value(s) to send
+        """
+        response = self.updi_phy.receive(1)
+        if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+            raise PymcuprogError("Error with st")
+
+        self.updi_phy.send(values)
+        response = self.updi_phy.receive(1)
+        if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+            raise PymcuprogError("Error with st")
+*/
+  unsigned char recv_buffer[1];
+  if (updi_physical_recv(pgm, recv_buffer, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI data phase recv failed on first ACK\n", progname);
+    return -1;
+  }
+  if (recv_buffer[0] != UPDI_PHY_ACK) {
+    avrdude_message(MSG_INFO, "%s: UPDI data phase expected first ACK\n", progname);
+    return -1;
+  }
+  if (updi_physical_send(pgm, buffer, size) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI data phase send failed\n", progname);
+    return -1;
+  }
+  if (updi_physical_recv(pgm, recv_buffer, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI data phase recv failed on second ACK\n", progname);
+    return -1;
+  }
+  if (recv_buffer[0] != UPDI_PHY_ACK) {
+    avrdude_message(MSG_INFO, "%s: UPDI data phase expected second ACK\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+int updi_link_st(PROGRAMMER * pgm, uint32_t address, uint8_t value)
+{
+/*
+    def st(self, address, value):
+        """
+        Store a single byte value directly to a 24-bit address
+
+        :param address: address to write to
+        :param value: value to write
+        """
+        self.logger.info("ST to 0x{0:06X}".format(address))
+        self.updi_phy.send(
+            [constants.UPDI_PHY_SYNC, constants.UPDI_STS | constants.UPDI_ADDRESS_24 | constants.UPDI_DATA_8,
+             address & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF])
+        return self._st_data_phase([value & 0xFF])
+*/
+  unsigned char send_buffer[5];
+  avrdude_message(MSG_DEBUG, "%s: ST to 0x%06X\n", progname, address);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_STS | UPDI_DATA_8 | (updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? UPDI_ADDRESS_24 : UPDI_ADDRESS_16);
+  send_buffer[2] = address & 0xFF;
+  send_buffer[3] = (address >> 8) & 0xFF;
+  send_buffer[4] = (address >> 16) & 0xFF;
+  if (updi_physical_send(pgm, send_buffer, updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? 5 : 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST operation send failed\n", progname);
+    return -1;
+  }
+  send_buffer[0] = value;
+  return updi_link_st_data_phase(pgm, send_buffer, 1);
+}
+
+int updi_link_st16(PROGRAMMER * pgm, uint32_t address, uint16_t value)
+{
+/*
+    def st16(self, address, value):
+        """
+        Store a 16-bit word value directly to a 24-bit address
+
+        :param address: address to write to
+        :param value: value to write
+        """
+        self.logger.info("ST to 0x{0:06X}".format(address))
+        self.updi_phy.send(
+            [constants.UPDI_PHY_SYNC, constants.UPDI_STS | constants.UPDI_ADDRESS_24 | constants.UPDI_DATA_16,
+             address & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF])
+        return self._st_data_phase([value & 0xFF, (value >> 8) & 0xFF])
+*/
+  unsigned char send_buffer[5];
+  avrdude_message(MSG_DEBUG, "%s: ST16 to 0x%06X\n", progname, address);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_STS | UPDI_DATA_16 | (updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? UPDI_ADDRESS_24 : UPDI_ADDRESS_16);
+  send_buffer[2] = address & 0xFF;
+  send_buffer[3] = (address >> 8) & 0xFF;
+  send_buffer[4] = (address >> 16) & 0xFF;
+  if (updi_physical_send(pgm, send_buffer, updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? 5 : 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST16 operation send failed\n", progname);
+    return -1;
+  }
+  send_buffer[0] = value & 0xFF;
+  send_buffer[1] = (value >> 8) & 0xFF;
+  return updi_link_st_data_phase(pgm, send_buffer, 2);
+}
+
+int updi_link_st_ptr(PROGRAMMER * pgm, uint32_t address)
+{
+/*
+    def st_ptr(self, address):
+        """
+        Set the pointer location
+
+        :param address: address to write
+        """
+        self.logger.info("ST to ptr")
+        self.updi_phy.send(
+            [constants.UPDI_PHY_SYNC, constants.UPDI_ST | constants.UPDI_PTR_ADDRESS | constants.UPDI_DATA_24,
+             address & 0xFF, (address >> 8) & 0xFF, (address >> 16) & 0xFF])
+        response = self.updi_phy.receive(1)
+        if len(response) != 1 or response[0] != constants.UPDI_PHY_ACK:
+            raise PymcuprogError("Error with st_ptr")
+*/
+  unsigned char send_buffer[5];
+  unsigned char recv_buffer[1];
+  avrdude_message(MSG_DEBUG, "%s: ST_PTR to 0x%06X\n", progname, address);
+  send_buffer[0] = UPDI_PHY_SYNC;
+  send_buffer[1] = UPDI_STS | UPDI_ST | UPDI_PTR_ADDRESS | (updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? UPDI_DATA_24 : UPDI_DATA_16);
+  send_buffer[2] = address & 0xFF;
+  send_buffer[3] = (address >> 8) & 0xFF;
+  send_buffer[4] = (address >> 16) & 0xFF;
+  if (updi_physical_send(pgm, send_buffer, updi_get_datalink_mode(pgm) == UPDI_LINK_MODE_24BIT ? 5 : 4) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR operation send failed\n", progname);
+    return -1;
+  }
+  if (updi_physical_recv(pgm, recv_buffer, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: UPDI ST_PTR recv failed on ACK\n", progname);
+    return -1;
+  }
+  if (recv_buffer[0] != UPDI_PHY_ACK) {
+    avrdude_message(MSG_INFO, "%s: UPDI ST_PTR expected ACK\n", progname);
+    return -1;
+  }
+  return 0;
+}
diff --git a/avrdude/updi_link.h b/avrdude/updi_link.h
new file mode 100644
index 00000000..e6848b0d
--- /dev/null
+++ b/avrdude/updi_link.h
@@ -0,0 +1,58 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef updi_link_h
+#define updi_link_h
+
+#include "libavrdude.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int updi_link_open(PROGRAMMER * pgm);
+void updi_link_close(PROGRAMMER * pgm);
+int updi_link_init(PROGRAMMER * pgm);
+int updi_link_ldcs(PROGRAMMER * pgm, uint8_t address, uint8_t * value);
+int updi_link_stcs(PROGRAMMER * pgm, uint8_t address, uint8_t value);
+int updi_link_ld_ptr_inc(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size);
+int updi_link_ld_ptr_inc16(PROGRAMMER * pgm, unsigned char * buffer, uint16_t words);
+int updi_link_st_ptr_inc(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size);
+int updi_link_st_ptr_inc16(PROGRAMMER * pgm, unsigned char * buffer, uint16_t words);
+int updi_link_repeat(PROGRAMMER * pgm, uint16_t repeats);
+int updi_link_read_sib(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size);
+int updi_link_key(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size_type, uint16_t size);
+int updi_link_ld(PROGRAMMER * pgm, uint32_t address, uint8_t * value);
+int updi_link_ld16(PROGRAMMER * pgm, uint32_t address, uint16_t * value);
+int updi_link_st(PROGRAMMER * pgm, uint32_t address, uint8_t value);
+int updi_link_st16(PROGRAMMER * pgm, uint32_t address, uint16_t value);
+int updi_link_st_ptr(PROGRAMMER * pgm, uint32_t address);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* updi_link_h */
diff --git a/avrdude/updi_nvm.c b/avrdude/updi_nvm.c
new file mode 100644
index 00000000..df8cc02c
--- /dev/null
+++ b/avrdude/updi_nvm.c
@@ -0,0 +1,1277 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#include "ac_cfg.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "avrdude.h"
+#include "libavrdude.h"
+#include "updi_nvm.h"
+#include "updi_state.h"
+#include "updi_constants.h"
+#include "updi_readwrite.h"
+
+typedef enum 
+{
+  DONT_USE_WORD_ACCESS,
+  USE_WORD_ACCESS
+} access_mode;
+
+#define USE_DEFAULT_COMMAND 0xFF
+
+static int nvm_chip_erase_V0(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def chip_erase(self):
+        """
+        Does a chip erase using the NVM controller
+
+        Note that on locked devices this is not possible
+        and the ERASE KEY has to be used instead, see the unlock method
+        """
+        self.logger.info("Chip erase using NVM CTRL")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before chip erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_CHIP_ERASE)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after chip erase")
+
+        return True
+*/
+  avrdude_message(MSG_DEBUG, "%s: Chip erase using NVM CTRL\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_CHIP_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Chip erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_flash_page_V0(PROGRAMMER * pgm, AVRPART * p, uint32_t address)
+{
+/*
+    def erase_flash_page(self, address):
+        """
+        Erasing single flash page using the NVM controller (v0)
+
+        :param address: Start address of page to erase
+        :type address: int
+        """
+        self.logger.info("Erase flash page at address 0x%08X", address)
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before flash page erase")
+
+        # Dummy write
+        self.readwrite.write_data(address, [0xFF])
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_ERASE_PAGE)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after flash page erase")
+*/
+  unsigned char data[1];
+  avrdude_message(MSG_DEBUG, "%s: Erase flash page at address 0x%06X\n", progname, address);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  data[0] = 0xFF;
+  if (updi_write_data(pgm, address, data, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: Dummy write operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_ERASE_PAGE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Flash page erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_eeprom_V0(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def erase_eeprom(self):
+        """
+        Erase EEPROM memory only (v0)
+        """
+        self.logger.info("Erase EEPROM")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before EEPROM erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_ERASE_EEPROM)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after EEPROM erase")
+*/  
+  avrdude_message(MSG_DEBUG, "%s: Erase EEPROM\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_ERASE_EEPROM) < 0) {
+    avrdude_message(MSG_INFO, "%s: EEPROM erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_user_row_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint16_t size)
+{
+/*
+    def erase_user_row(self, address, size):
+        """
+        Erase User Row memory only (v0)
+
+        :param address: Start address of user row
+        :type address: int
+        """
+        self.logger.info("Erase user row")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before user row erase")
+
+        # On this NVM version user row is implemented as EEPROM
+        # When erasing single EEPROM pages a dummy write is needed for each location to be erased
+        for offset in range(size):
+            self.readwrite.write_data(address+offset, [0xFF])
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_ERASE_PAGE)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after user row erase")
+*/
+  uint16_t offset;
+  unsigned char data[1];
+  avrdude_message(MSG_DEBUG, "%s: Erase user row\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  data[0]=0xFF;
+  for (offset = 0; offset<size; offset++)
+  {
+    if (updi_write_data(pgm, address+offset, data, 1) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data operation failed at offset 0x%04x\n", progname, offset);
+      return -1;
+    }
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_ERASE_PAGE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Erase page operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_write_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode, uint8_t nvm_command);
+
+static int nvm_write_eeprom_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size);
+
+
+static int nvm_write_flash_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_flash(self, address, data):
+        """
+        Writes data to flash (v0)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_nvm(address, data, use_word_access=True)
+*/
+  return nvm_write_V0(pgm, p, address, buffer, size, USE_WORD_ACCESS, USE_DEFAULT_COMMAND);
+}
+
+static int nvm_write_user_row_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_user_row(self, address, data):
+        """
+        Writes data to user row (v0)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        # On this NVM variant user row is implemented as EEPROM
+        return self.write_eeprom(address, data)
+*/
+  return nvm_write_eeprom_V0(pgm, p, address, buffer, size);
+}
+
+static int nvm_write_eeprom_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_eeprom(self, address, data):
+        """
+        Write data to EEPROM (v0)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_nvm(address, data, use_word_access=False,
+                              nvmcommand=constants.UPDI_V0_NVMCTRL_CTRLA_ERASE_WRITE_PAGE)
+*/
+  return nvm_write_V0(pgm, p, address, buffer, size, DONT_USE_WORD_ACCESS, UPDI_V0_NVMCTRL_CTRLA_ERASE_WRITE_PAGE);
+}
+
+static int nvm_write_fuse_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint8_t value)
+{
+/*
+    def write_fuse(self, address, data):
+        """
+        Writes one fuse value (v0)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+
+        # Check that NVM controller is ready
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready before fuse write")
+
+        # Write address to NVMCTRL ADDR
+        self.logger.debug("Load NVM address")
+        self.readwrite.write_byte(self.device.nvmctrl_address + constants.UPDI_NVMCTRL_ADDRL, address & 0xFF)
+        self.readwrite.write_byte(self.device.nvmctrl_address + constants.UPDI_NVMCTRL_ADDRH, (address >> 8) & 0xFF)
+
+        # Write data
+        self.logger.debug("Load fuse data")
+        self.readwrite.write_byte(self.device.nvmctrl_address + constants.UPDI_NVMCTRL_DATAL, data[0] & 0xFF)
+
+        # Execute
+        self.logger.debug("Execute fuse write")
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_WRITE_FUSE)
+
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready after fuse write")
+*/
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Load NVM address\n", progname);
+  if (updi_write_byte(pgm, p->nvm_base + UPDI_NVMCTRL_ADDRL, address & 0xFF) < 0) {
+    avrdude_message(MSG_INFO, "%s: Write ADDRL operation failed\n", progname);
+    return -1;
+  }
+  if (updi_write_byte(pgm, p->nvm_base + UPDI_NVMCTRL_ADDRH, (address >> 8) & 0xFF) < 0) {
+    avrdude_message(MSG_INFO, "%s: Write ADDRH operation failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Load fuse data\n", progname);
+  if (updi_write_byte(pgm, p->nvm_base + UPDI_NVMCTRL_DATAL, value & 0xFF) < 0) {
+    avrdude_message(MSG_INFO, "%s: Write DATAL operation failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Execute fuse write\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_WRITE_FUSE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Write fuse operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_write_V0(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode, uint8_t nvm_command)
+{
+/*
+    def write_nvm(self, address, data, use_word_access, nvmcommand=constants.UPDI_V0_NVMCTRL_CTRLA_WRITE_PAGE):
+        """
+        Writes a page of data to NVM (v0)
+
+        By default the PAGE_WRITE command is used, which
+        requires that the page is already erased.
+        By default word access is used (flash)
+
+        :param address: address to write to
+        :param data: data to write
+        :param use_word_access: write whole words?
+        :param nvmcommand: command to use for commit
+        """
+
+        # Check that NVM controller is ready
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready before page buffer clear")
+
+        # Clear the page buffer
+        self.logger.debug("Clear page buffer")
+        self.execute_nvm_command(constants.UPDI_V0_NVMCTRL_CTRLA_PAGE_BUFFER_CLR)
+
+        # Wait for NVM controller to be ready
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready after page buffer clear")
+
+        # Load the page buffer by writing directly to location
+        if use_word_access:
+            self.readwrite.write_data_words(address, data)
+        else:
+            self.readwrite.write_data(address, data)
+
+        # Write the page to NVM, maybe erase first
+        self.logger.debug("Committing data")
+        self.execute_nvm_command(nvmcommand)
+
+        # Wait for NVM controller to be ready again
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready after page write")
+*/
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Clear page buffer\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V0_NVMCTRL_CTRLA_PAGE_BUFFER_CLR) < 0) {
+    avrdude_message(MSG_INFO, "%s: Clear page operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (mode == USE_WORD_ACCESS) {
+    if (updi_write_data_words(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data words operation failed\n", progname);
+      return -1;
+    }
+  } else {
+    if (updi_write_data(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data operation failed\n", progname);
+      return -1;
+    }
+  }
+  avrdude_message(MSG_DEBUG, "%s: Committing data\n", progname);
+  if (nvm_command == USE_DEFAULT_COMMAND) {
+    nvm_command = UPDI_V0_NVMCTRL_CTRLA_WRITE_PAGE;
+  }
+  if (updi_nvm_command(pgm, p, nvm_command) < 0) {
+      avrdude_message(MSG_INFO, "%s: Commit data command failed\n", progname);
+      return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_chip_erase_V2(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def chip_erase(self):
+        """
+        Does a chip erase using the NVM controller
+        Note that on locked devices this it not possible
+        and the ERASE KEY has to be used instead
+        """
+        self.logger.info("Chip erase using NVM CTRL")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM controller to be ready before chip erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_CHIP_ERASE)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM controller to be ready after chip erase")
+
+        return True
+*/
+  avrdude_message(MSG_DEBUG, "%s: Chip erase using NVM CTRL\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_CHIP_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Chip erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_flash_page_V2(PROGRAMMER * pgm, AVRPART * p, uint32_t address)
+{
+/*
+    def erase_flash_page(self, address):
+        """
+        Erasing single flash page using the NVM controller (v1)
+
+        :param address: Start address of page to erase
+        :type address: int
+        """
+        self.logger.info("Erase flash page at address 0x%08X", address)
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before flash page erase")
+
+        # Erase command
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_FLASH_PAGE_ERASE)
+
+        # Dummy write
+        self.readwrite.write_data(address, [0xFF])
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after flash page erase")
+
+        # Remove command from NVM controller
+        self.logger.debug("Clear NVM command")
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_NOCMD)
+*/
+  unsigned char data[1];
+  avrdude_message(MSG_DEBUG, "%s: Erase flash page at address 0x%06X\n", progname, address);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  data[0] = 0xFF;
+  if (updi_write_data(pgm, address, data, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: Dummy write operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_FLASH_PAGE_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Flash page erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_eeprom_V2(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def erase_eeprom(self):
+        """
+        Erase EEPROM memory only (v1)
+        """
+        self.logger.info("Erase EEPROM")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before EEPROM erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE)
+
+        # And wait for it
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready after EEPROM erase")
+
+        # Remove command from NVM controller
+        self.logger.debug("Clear NVM command")
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_NOCMD)
+*/
+  avrdude_message(MSG_DEBUG, "%s: Erase EEPROM\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: EEPROM erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Clear NVM command\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Sending empty command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_user_row_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint16_t size)
+{
+/*
+    def erase_user_row(self, address, size):
+        """
+        Erase User Row memory only (v1)
+
+        :param address: Start address of user row
+        :type address: int
+        """
+        # size is not used for this NVM version
+        _dummy = size
+        # On this NVM version user row is implemented as flash
+        return self.erase_flash_page(address)
+*/
+  return nvm_erase_flash_page_V2(pgm, p, address);
+}
+
+static int nvm_write_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode);
+
+static int nvm_write_flash_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_flash(self, address, data):
+        """
+        Writes data to flash (v1)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_nvm(address, data, use_word_access=True)
+*/
+  return nvm_write_V2(pgm, p, address, buffer, size, USE_WORD_ACCESS);
+}
+
+static int nvm_write_user_row_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_user_row(self, address, data):
+        """
+        Writes data to user row (v1)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        # On this NVM variant user row is implemented as Flash
+        return self.write_nvm(address, data, use_word_access=False)
+*/
+  return nvm_write_V2(pgm, p, address, buffer, size, DONT_USE_WORD_ACCESS);
+}
+
+static int nvm_write_eeprom_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_eeprom(self, address, data):
+        """
+        Writes data to NVM (EEPROM)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        nvm_command = constants.UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE_WRITE
+
+        # Check that NVM controller is ready
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM ready before command write")
+
+        # Write the command to the NVM controller
+        self.logger.info("NVM EEPROM erase/write command")
+        self.execute_nvm_command(nvm_command)
+
+        # Write the data
+        self.readwrite.write_data(address, data)
+
+        # Wait for NVM controller to be ready again
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM ready after data write")
+
+        # Remove command from NVM controller
+        self.logger.info("Clear NVM command")
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_NOCMD)
+*/
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: NVM EEPROM erase/write command\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_EEPROM_ERASE_WRITE) < 0) {
+    avrdude_message(MSG_INFO, "%s: EEPROM erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_write_data(pgm, address, buffer, size) < 0) {
+    avrdude_message(MSG_INFO, "%s: Write data operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Clear NVM command\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Clear NVM command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_write_fuse_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint8_t value)
+{
+/*
+    def write_fuse(self, address, data):
+        """
+        Writes one fuse value
+        V1 fuses are EEPROM-based
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_eeprom(address, data)
+*/
+  unsigned char buffer[1];
+  buffer[0]=value;
+  return nvm_write_eeprom_V2(pgm, p, address, buffer, 1);
+}
+
+static int nvm_write_V2(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode)
+{
+/*
+    def write_nvm(self, address, data, use_word_access):
+        """
+        Writes data to NVM (version 1)
+        This version of the NVM block has no page buffer, so words are written directly.
+
+        :param address: address to write to
+        :param data: data to write
+        :param use_word_access: write in whole words?
+        """
+        nvm_command = constants.UPDI_V2_NVMCTRL_CTRLA_FLASH_WRITE
+
+        # Check that NVM controller is ready
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM controller to be ready before page buffer clear")
+
+        # Write the command to the NVM controller
+        self.logger.info("NVM write command")
+        self.execute_nvm_command(nvm_command)
+
+        # Write the data
+        if use_word_access:
+            self.readwrite.write_data_words(address, data)
+        else:
+            self.readwrite.write_data(address, data)
+
+        # Wait for NVM controller to be ready again
+        if not self.wait_nvm_ready():
+            raise Exception("Timeout waiting for NVM controller to be ready after data write")
+
+        # Remove command from NVM controller
+        self.logger.info("Clear NVM command")
+        self.execute_nvm_command(constants.UPDI_V2_NVMCTRL_CTRLA_NOCMD)
+*/
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: NVM write command\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_FLASH_WRITE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Clear page operation failed\n", progname);
+    return -1;
+  }
+  if (mode == USE_WORD_ACCESS) {
+    if (updi_write_data_words(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data words operation failed\n", progname);
+      return -1;
+    }
+  } else {
+    if (updi_write_data(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data operation failed\n", progname);
+      return -1;
+    }
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Clear NVM command\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V2_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Clear NVM command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_chip_erase_V3(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def chip_erase(self):
+        """
+        Does a chip erase using the NVM controller
+
+        Note that on locked devices this is not possible
+        and the ERASE KEY has to be used instead, see the unlock method
+        """
+        self.logger.info("Chip erase using NVM CTRL")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before chip erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_CHIP_ERASE)
+
+        # And wait for it
+        status = self.wait_nvm_ready()
+
+        # Remove command
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_NOCMD)
+
+        if not status:
+            raise IOError("Timeout waiting for NVM controller to be ready after chip erase")
+
+        return True
+*/
+  avrdude_message(MSG_DEBUG, "%s: Chip erase using NVM CTRL\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_CHIP_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Chip erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Sending empty command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_flash_page_V3(PROGRAMMER * pgm, AVRPART * p, uint32_t address)
+{
+/*
+    def erase_flash_page(self, address):
+        """
+        Erasing single flash page using the NVM controller (v3)
+
+        :param address: Start address of page to erase
+        :type address: int
+        """
+        self.logger.info("Erase flash page at address 0x%08X", address)
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before flash page erase")
+
+        # Dummy write
+        self.readwrite.write_data(address, [0xFF])
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_ERASE)
+
+        # And wait for it
+        status = self.wait_nvm_ready()
+
+        # Remove command
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_NOCMD)
+
+        if not status:
+            raise IOError("Timeout waiting for NVM controller to be ready after flash page erase")
+*/  
+  unsigned char data[1];
+  avrdude_message(MSG_DEBUG, "%s: Erase flash page at address 0x%06X\n", progname, address);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  data[0] = 0xFF;
+  if (updi_write_data(pgm, address, data, 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: Dummy write operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: Flash page erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_eeprom_V3(PROGRAMMER * pgm, AVRPART * p)
+{
+/*
+    def erase_eeprom(self):
+        """
+        Erase EEPROM memory only
+        """
+        self.logger.info("Erase EEPROM")
+
+        # Wait until NVM CTRL is ready to erase
+        if not self.wait_nvm_ready():
+            raise IOError("Timeout waiting for NVM controller to be ready before EEPROM erase")
+
+        # Erase
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_EEPROM_ERASE)
+
+        # And wait for it
+        status = self.wait_nvm_ready()
+
+        # Remove command
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_NOCMD)
+
+        if not status:
+            raise IOError("Timeout waiting for NVM controller to be ready after EEPROM erase")
+*/
+  avrdude_message(MSG_DEBUG, "%s: Erase EEPROM\n", progname);
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_EEPROM_ERASE) < 0) {
+    avrdude_message(MSG_INFO, "%s: EEPROM erase command failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Sending empty command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+static int nvm_erase_user_row_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint16_t size)
+{
+/*
+    def erase_user_row(self, address, size):
+        """
+        Erase User Row memory only
+
+        :param address: Start address of user row
+        :type address: int
+        """
+        self.logger.info("Erase user row")
+
+        # On this NVM version user row is implemented as FLASH
+        return self.erase_flash_page(self, address)
+*/
+  avrdude_message(MSG_DEBUG, "%s: Erase user row at address 0x%06X\n", progname, address);
+  
+  return nvm_erase_flash_page_V3(pgm, p, address);
+}
+
+static int nvm_write_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode, uint8_t nvm_command);
+
+static int nvm_write_flash_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_flash(self, address, data):
+        """
+        Writes data to flash (v3)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_nvm(address, data, use_word_access=True)
+*/
+  return nvm_write_V3(pgm, p, address, buffer, size, USE_WORD_ACCESS, USE_DEFAULT_COMMAND);
+}
+
+static int nvm_write_user_row_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_user_row(self, address, data):
+        """
+        Writes data to user row (v3)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        # On this NVM variant user row is implemented as FLASH
+        return self.write_nvm(address, data, use_word_access=True)
+*/
+  return nvm_write_V3(pgm, p, address, buffer, size, USE_WORD_ACCESS, USE_DEFAULT_COMMAND);
+}
+
+static int nvm_write_eeprom_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+/*
+    def write_eeprom(self, address, data):
+        """
+        Write data to EEPROM (v3)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_nvm(address, data, use_word_access=False,
+                              nvmcommand=constants.UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_ERASE_WRITE)
+*/
+  return nvm_write_V3(pgm, p, address, buffer, size, DONT_USE_WORD_ACCESS, UPDI_V3_NVMCTRL_CTRLA_EEPROM_PAGE_ERASE_WRITE);
+}
+
+static int nvm_write_fuse_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint8_t value)
+{
+/*
+    def write_fuse(self, address, data):
+        """
+        Writes one fuse value (v3)
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        return self.write_eeprom(address, data)
+*/
+  unsigned char buffer[1];
+  buffer[0] = value;
+  return nvm_write_eeprom_V3(pgm, p, address, buffer, 1);
+}
+
+static int nvm_write_V3(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, 
+                        uint16_t size, access_mode mode, uint8_t nvm_command)
+{
+/*
+    def write_nvm(self, address, data, use_word_access, nvmcommand=constants.UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_WRITE):
+        """
+        Writes a page of data to NVM (v3)
+
+        By default the PAGE_WRITE command is used, which
+        requires that the page is already erased.
+        By default word access is used (flash)
+
+        :param address: address to write to
+        :param data: data to write
+        :param use_word_access: write whole words?
+        :param nvmcommand: command to use for commit
+        """
+
+        # Check that NVM controller is ready
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready before page buffer clear")
+
+        # Clear the page buffer
+        self.logger.debug("Clear page buffer")
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_BUFFER_CLEAR)
+
+        # Wait for NVM controller to be ready
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready after page buffer clear")
+
+        # Load the page buffer by writing directly to location
+        if use_word_access:
+            self.readwrite.write_data_words(address, data)
+        else:
+            self.readwrite.write_data(address, data)
+
+        # Write the page to NVM, maybe erase first
+        self.logger.debug("Committing data")
+        self.execute_nvm_command(nvmcommand)
+
+        # Wait for NVM controller to be ready again
+        if not self.wait_nvm_ready():
+            raise PymcuprogError("Timeout waiting for NVM controller to be ready after page write")
+
+        # Remove command
+        self.execute_nvm_command(constants.UPDI_V3_NVMCTRL_CTRLA_NOCMD)
+*/
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  avrdude_message(MSG_DEBUG, "%s: Clear page buffer\n", progname);
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_BUFFER_CLEAR) < 0) {
+    avrdude_message(MSG_INFO, "%s: Clear page operation failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (mode == USE_WORD_ACCESS) {
+    if (updi_write_data_words(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data words operation failed\n", progname);
+      return -1;
+    }
+  } else {
+    if (updi_write_data(pgm, address, buffer, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Write data operation failed\n", progname);
+      return -1;
+    }
+  }
+  avrdude_message(MSG_DEBUG, "%s: Committing data\n", progname);
+  if (nvm_command == USE_DEFAULT_COMMAND) {
+    nvm_command = UPDI_V3_NVMCTRL_CTRLA_FLASH_PAGE_WRITE;
+  }
+  if (updi_nvm_command(pgm, p, nvm_command) < 0) {
+      avrdude_message(MSG_INFO, "%s: Commit data command failed\n", progname);
+      return -1;
+  }
+  if (updi_nvm_wait_ready(pgm, p) < 0) {
+    avrdude_message(MSG_INFO, "%s: Wait for ready chip failed\n", progname);
+    return -1;
+  }
+  if (updi_nvm_command(pgm, p, UPDI_V3_NVMCTRL_CTRLA_NOCMD) < 0) {
+    avrdude_message(MSG_INFO, "%s: Sending empty command failed\n", progname);
+    return -1;
+  }
+  return 0;
+}
+
+
+int updi_nvm_chip_erase(PROGRAMMER * pgm, AVRPART * p)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_chip_erase_V0(pgm, p);
+    case UPDI_NVM_MODE_V2:
+      return nvm_chip_erase_V2(pgm, p);
+    case UPDI_NVM_MODE_V3:
+      return nvm_chip_erase_V3(pgm, p);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_erase_flash_page(PROGRAMMER * pgm, AVRPART *p, uint32_t address)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_erase_flash_page_V0(pgm, p, address);
+    case UPDI_NVM_MODE_V2:
+      return nvm_erase_flash_page_V2(pgm, p, address);
+    case UPDI_NVM_MODE_V3:
+      return nvm_erase_flash_page_V3(pgm, p, address);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_erase_eeprom(PROGRAMMER * pgm, AVRPART *p)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_erase_eeprom_V0(pgm, p);
+    case UPDI_NVM_MODE_V2:
+      return nvm_erase_eeprom_V2(pgm, p);
+    case UPDI_NVM_MODE_V3:
+      return nvm_erase_eeprom_V3(pgm, p);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_erase_user_row(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint16_t size)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_erase_user_row_V0(pgm, p, address, size);
+    case UPDI_NVM_MODE_V2:
+      return nvm_erase_user_row_V2(pgm, p, address, size);
+    case UPDI_NVM_MODE_V3:
+      return nvm_erase_user_row_V3(pgm, p, address, size);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_write_flash(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_write_flash_V0(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V2:
+      return nvm_write_flash_V2(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V3:
+      return nvm_write_flash_V3(pgm, p, address, buffer, size);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_write_user_row(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_write_user_row_V0(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V2:
+      return nvm_write_user_row_V2(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V3:
+      return nvm_write_user_row_V3(pgm, p, address, buffer, size);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_write_eeprom(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_write_eeprom_V0(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V2:
+      return nvm_write_eeprom_V2(pgm, p, address, buffer, size);
+    case UPDI_NVM_MODE_V3:
+      return nvm_write_eeprom_V3(pgm, p, address, buffer, size);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_write_fuse(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint8_t value)
+{
+  switch(updi_get_nvm_mode(pgm))
+  {
+    case UPDI_NVM_MODE_V0:
+      return nvm_write_fuse_V0(pgm, p, address, value);
+    case UPDI_NVM_MODE_V2:
+      return nvm_write_fuse_V2(pgm, p, address, value);
+    case UPDI_NVM_MODE_V3:
+      return nvm_write_fuse_V3(pgm, p, address, value);
+    default:
+      avrdude_message(MSG_INFO, "%s: Invalid NVM Mode %d\n", progname, updi_get_nvm_mode(pgm));
+      return -1;
+  }
+}
+
+int updi_nvm_wait_ready(PROGRAMMER * pgm, AVRPART *p)
+{
+/*
+    def wait_nvm_ready(self):
+        """
+        Waits for the NVM controller to be ready
+        """
+        timeout = Timeout(10000)  # 10 sec timeout, just to be sure
+
+        self.logger.debug("Wait NVM ready")
+        while not timeout.expired():
+            status = self.readwrite.read_byte(self.device.nvmctrl_address + constants.UPDI_NVMCTRL_STATUS)
+            if status & (1 << constants.UPDI_NVM_STATUS_WRITE_ERROR):
+                self.logger.error("NVM error")
+                return False
+
+            if not status & ((1 << constants.UPDI_NVM_STATUS_EEPROM_BUSY) |
+                             (1 << constants.UPDI_NVM_STATUS_FLASH_BUSY)):
+                return True
+
+        self.logger.error("Wait NVM ready timed out")
+        return False
+*/
+  unsigned long start_time;
+  unsigned long current_time;
+  struct timeval tv;
+  uint8_t status;
+  gettimeofday (&tv, NULL);
+  start_time = (tv.tv_sec * 1000000) + tv.tv_usec;
+  do {
+    if (updi_read_byte(pgm, p->nvm_base + UPDI_NVMCTRL_STATUS, &status) < 0){
+      avrdude_message(MSG_INFO, "%s: Status read operation failed\n", progname);
+      return -1;
+    }
+    if (status & (1 << UPDI_NVM_STATUS_WRITE_ERROR)) {
+      avrdude_message(MSG_INFO, "%s: NVM error\n", progname);
+      return -1;
+    }
+    if (!(status & ((1 << UPDI_NVM_STATUS_EEPROM_BUSY) | 
+                    (1 << UPDI_NVM_STATUS_FLASH_BUSY)))) {
+      return 0;
+    }
+    gettimeofday (&tv, NULL);
+    current_time = (tv.tv_sec * 1000000) + tv.tv_usec;
+  } while ((current_time - start_time) < 10000000);
+
+  avrdude_message(MSG_INFO, "%s: Wait NVM ready timed out\n", progname);
+  return -1;
+}
+
+int updi_nvm_command(PROGRAMMER * pgm, AVRPART *p, uint8_t command)
+{
+/*
+    def execute_nvm_command(self, command):
+        """
+        Executes an NVM COMMAND on the NVM CTRL
+
+        :param command: command to execute
+        """
+        self.logger.debug("NVMCMD %d executing", command)
+        return self.readwrite.write_byte(self.device.nvmctrl_address + constants.UPDI_NVMCTRL_CTRLA, command)
+*/
+  avrdude_message(MSG_DEBUG, "%s: NVMCMD %d executing\n", progname, command);
+
+  return updi_write_byte(pgm, p->nvm_base + UPDI_NVMCTRL_CTRLA, command);
+}
diff --git a/avrdude/updi_nvm.h b/avrdude/updi_nvm.h
new file mode 100644
index 00000000..c0c1544e
--- /dev/null
+++ b/avrdude/updi_nvm.h
@@ -0,0 +1,51 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef updi_nvm_h
+#define updi_nvm_h
+
+#include "libavrdude.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int updi_nvm_chip_erase(PROGRAMMER * pgm, AVRPART * p);
+int updi_nvm_erase_flash_page(PROGRAMMER * pgm, AVRPART *p, uint32_t address);
+int updi_nvm_erase_eeprom(PROGRAMMER * pgm, AVRPART *p);
+int updi_nvm_erase_user_row(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint16_t size);
+int updi_nvm_write_flash(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size);
+int updi_nvm_write_user_row(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size);
+int updi_nvm_write_eeprom(PROGRAMMER * pgm, AVRPART *p, uint32_t address, unsigned char * buffer, uint16_t size);
+int updi_nvm_write_fuse(PROGRAMMER * pgm, AVRPART *p, uint32_t address, uint8_t value);
+int updi_nvm_wait_ready(PROGRAMMER * pgm, AVRPART *p);
+int updi_nvm_command(PROGRAMMER * pgm, AVRPART *p, uint8_t command);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* updi_nvm_h */
diff --git a/avrdude/updi_readwrite.c b/avrdude/updi_readwrite.c
new file mode 100644
index 00000000..f36015b8
--- /dev/null
+++ b/avrdude/updi_readwrite.c
@@ -0,0 +1,320 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#include "ac_cfg.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "avrdude.h"
+#include "libavrdude.h"
+#include "updi_constants.h"
+#include "updi_link.h"
+#include "updi_readwrite.h"
+
+int updi_read_cs(PROGRAMMER * pgm, uint8_t address, uint8_t * value)
+{
+/*
+    def read_cs(self, address):
+        """
+        Read from Control/Status space
+
+        :param address: address (index) to read
+        :return: value read
+        """
+        return self.datalink.ldcs(address)
+*/
+  return updi_link_ldcs(pgm, address, value);
+}
+
+int updi_write_cs(PROGRAMMER * pgm, uint8_t address, uint8_t value)
+{
+/*
+    def write_cs(self, address, value):
+        """
+        Write to Control/Status space
+
+        :param address: address (index) to write
+        :param value: 8-bit value to write
+        """
+        return self.datalink.stcs(address, value)
+*/
+  return updi_link_stcs(pgm, address, value);
+}
+
+int updi_write_key(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size_type, uint16_t size)
+{
+/*
+    def write_key(self, size, key):
+        """
+        Write a KEY into UPDI
+
+        :param size: size of key to send
+        :param key: key value
+        """
+        return self.datalink.key(size, key)
+*/
+  return updi_link_key(pgm, buffer, size_type, size);
+}
+
+int updi_read_sib(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size)
+{
+/*
+    def read_sib(self):
+        """
+        Read the SIB from UPDI
+
+        :return: SIB string (bytearray) read
+        """
+        return self.datalink.read_sib()
+*/
+  return updi_link_read_sib(pgm, buffer, size);
+}
+
+int updi_read_byte(PROGRAMMER * pgm, uint32_t address, uint8_t * value)
+{
+/*
+    def read_byte(self, address):
+        """
+        Read a single byte from UPDI
+
+        :param address: address to read from
+        :return: value read
+        """
+        return self.datalink.ld(address)
+*/
+  return updi_link_ld(pgm, address, value);
+}
+
+int updi_write_byte(PROGRAMMER * pgm, uint32_t address, uint8_t value)
+{
+/*
+    def write_byte(self, address, value):
+        """
+        Writes a single byte to UPDI
+
+        :param address: address to write to
+        :param value: value to write
+        """
+        return self.datalink.st(address, value)
+*/
+  return updi_link_st(pgm, address, value);
+}
+
+int updi_read_data(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size)
+{
+/*
+    def read_data(self, address, size):
+        """
+        Reads a number of bytes of data from UPDI
+
+        :param address: address to write to
+        :param size: number of bytes to read
+        """
+        self.logger.debug("Reading %d bytes from 0x%04X", size, address)
+        # Range check
+        if size > constants.UPDI_MAX_REPEAT_SIZE:
+            raise PymcuprogError("Cant read that many bytes in one go")
+
+        # Store the address
+        self.datalink.st_ptr(address)
+
+        # Fire up the repeat
+        if size > 1:
+            self.datalink.repeat(size)
+
+        # Do the read(s)
+        return self.datalink.ld_ptr_inc(size)
+*/
+  avrdude_message(MSG_DEBUG, "%s: Reading %d bytes from 0x%06X", progname, size, address);
+
+  if (size > UPDI_MAX_REPEAT_SIZE) {
+    avrdude_message(MSG_INFO, "%s: Can't read that many bytes in one go\n", progname);
+    return -1;
+  }
+
+  if (updi_link_st_ptr(pgm, address) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR operation failed\n", progname);
+    return -1;
+  }
+
+  if (size > 1) {
+    if (updi_link_repeat(pgm, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Repeat operation failed\n", progname);
+      return -1;
+    }
+  }
+  return updi_link_ld_ptr_inc(pgm, buffer, size);
+}
+
+int updi_write_data(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size)
+{
+/*
+    def write_data(self, address, data):
+        """
+        Writes a number of bytes to memory
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        # Special case of 1 byte
+        if len(data) == 1:
+            return self.datalink.st(address, data[0])
+        # Special case of 2 byte
+        if len(data) == 2:
+            self.datalink.st(address, data[0])
+            return self.datalink.st(address + 1, data[1])
+
+        # Range check
+        if len(data) > constants.UPDI_MAX_REPEAT_SIZE:
+            raise PymcuprogError("Invalid length")
+
+        # Store the address
+        self.datalink.st_ptr(address)
+
+        # Fire up the repeat
+        self.datalink.repeat(len(data))
+        return self.datalink.st_ptr_inc(data)
+*/
+  if (size == 1) {
+    return updi_link_st(pgm, address, buffer[0]);
+  }
+  if (size == 2) {
+    if (updi_link_st(pgm, address, buffer[0]) < 0) {
+      avrdude_message(MSG_INFO, "%s: ST operation failed\n", progname);
+      return -1;
+    }
+    return updi_link_st(pgm, address+1, buffer[1]);
+  }
+  if (size > UPDI_MAX_REPEAT_SIZE) {
+    avrdude_message(MSG_INFO, "%s: Invalid length\n", progname);
+    return -1;
+  }
+  if (updi_link_st_ptr(pgm, address) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR operation failed\n", progname);
+    return -1;
+  }
+  if (updi_link_repeat(pgm, size) < 0) {
+    avrdude_message(MSG_INFO, "%s: Repeat operation failed\n", progname);
+    return -1;
+  }
+  return updi_link_st_ptr_inc(pgm, buffer, size);
+}
+
+int updi_read_data_words(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size)
+{
+/*
+    def read_data_words(self, address, words):
+        """
+        Reads a number of words of data from UPDI
+
+        :param address: address to write to
+        :param words: number of words to read
+        """
+        self.logger.debug("Reading %d words from 0x%04X", words, address)
+
+        # Range check
+        if words > constants.UPDI_MAX_REPEAT_SIZE >> 1:
+            raise PymcuprogError("Cant read that many words in one go")
+
+        # Store the address
+        self.datalink.st_ptr(address)
+
+        # Fire up the repeat
+        if words > 1:
+            self.datalink.repeat(words)
+
+        # Do the read
+        return self.datalink.ld_ptr_inc16(words)
+*/
+  avrdude_message(MSG_DEBUG, "%s: Reading %d words from 0x%06X", progname, size, address);
+
+  if (size > (UPDI_MAX_REPEAT_SIZE >> 1)) {
+    avrdude_message(MSG_INFO, "%s: Can't read that many words in one go\n", progname);
+    return -1;
+  }
+
+  if (updi_link_st_ptr(pgm, address) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR operation failed\n", progname);
+    return -1;
+  }
+
+  if (size > 1) {
+    if (updi_link_repeat(pgm, size) < 0) {
+      avrdude_message(MSG_INFO, "%s: Repeat operation failed\n", progname);
+      return -1;
+    }
+  }
+  return updi_link_ld_ptr_inc16(pgm, buffer, size);
+}
+
+int updi_write_data_words(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size)
+{
+/*
+    def write_data_words(self, address, data):
+        """
+        Writes a number of words to memory
+
+        :param address: address to write to
+        :param data: data to write
+        """
+        # Special-case of 1 word
+        if len(data) == 2:
+            value = data[0] + (data[1] << 8)
+            return self.datalink.st16(address, value)
+
+        # Range check
+        if len(data) > constants.UPDI_MAX_REPEAT_SIZE << 1:
+            raise PymcuprogError("Invalid length")
+
+        # Store the address
+        self.datalink.st_ptr(address)
+
+        # Fire up the repeat
+        self.datalink.repeat(len(data) >> 1)
+        return self.datalink.st_ptr_inc16(data)
+*/
+  if (size == 2) {
+    return updi_link_st16(pgm, address, buffer[0] + (buffer[1] << 8));
+  }
+  if (size > UPDI_MAX_REPEAT_SIZE << 1) {
+    avrdude_message(MSG_INFO, "%s: Invalid length\n", progname);
+    return -1;
+  }
+  if (updi_link_st_ptr(pgm, address) < 0) {
+    avrdude_message(MSG_INFO, "%s: ST_PTR operation failed\n", progname);
+    return -1;
+  }
+  if (updi_link_repeat(pgm, size >> 1) < 0) {
+    avrdude_message(MSG_INFO, "%s: Repeat operation failed\n", progname);
+    return -1;
+  }
+  return updi_link_st_ptr_inc16(pgm, buffer, size);
+}
diff --git a/avrdude/updi_readwrite.h b/avrdude/updi_readwrite.h
new file mode 100644
index 00000000..9519d179
--- /dev/null
+++ b/avrdude/updi_readwrite.h
@@ -0,0 +1,51 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef updi_readwrite_h
+#define updi_readwrite_h
+
+#include "libavrdude.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int updi_read_cs(PROGRAMMER * pgm, uint8_t address, uint8_t * value);
+int updi_write_cs(PROGRAMMER * pgm, uint8_t address, uint8_t value);
+int updi_write_key(PROGRAMMER * pgm, unsigned char * buffer, uint8_t size_type, uint16_t size);
+int updi_read_sib(PROGRAMMER * pgm, unsigned char * buffer, uint16_t size);
+int updi_read_byte(PROGRAMMER * pgm, uint32_t address, uint8_t * value);
+int updi_write_byte(PROGRAMMER * pgm, uint32_t address, uint8_t value);
+int updi_read_data(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size);
+int updi_write_data(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size);
+int updi_read_data_words(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size);
+int updi_write_data_words(PROGRAMMER * pgm, uint32_t address, uint8_t * buffer, uint16_t size);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* updi_readwrite_h */
diff --git a/avrdude/updi_state.c b/avrdude/updi_state.c
new file mode 100644
index 00000000..63d80f46
--- /dev/null
+++ b/avrdude/updi_state.c
@@ -0,0 +1,55 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#include "ac_cfg.h"
+
+#include "libavrdude.h"
+#include "updi_state.h"
+
+updi_sib_info* updi_get_sib_info(PROGRAMMER * pgm)
+{
+  return &((updi_state *)(pgm->cookie))->sib_info;
+}
+
+updi_datalink_mode updi_get_datalink_mode(PROGRAMMER * pgm)
+{
+  return ((updi_state *)(pgm->cookie))->datalink_mode;
+}
+
+void updi_set_datalink_mode(PROGRAMMER * pgm, updi_datalink_mode mode)
+{
+  ((updi_state *)(pgm->cookie))->datalink_mode = mode;
+}
+
+updi_nvm_mode updi_get_nvm_mode(PROGRAMMER * pgm)
+{
+  return ((updi_state *)(pgm->cookie))->nvm_mode;
+}
+
+void updi_set_nvm_mode(PROGRAMMER * pgm, updi_nvm_mode mode)
+{
+  ((updi_state *)(pgm->cookie))->nvm_mode = mode;
+}
diff --git a/avrdude/updi_state.h b/avrdude/updi_state.h
new file mode 100644
index 00000000..d4e39d4c
--- /dev/null
+++ b/avrdude/updi_state.h
@@ -0,0 +1,85 @@
+/*
+ * avrdude - A Downloader/Uploader for AVR device programmers
+ * Copyright (C) 2021  Dawid Buchwald
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* $Id$ */
+
+/*
+ * Based on pymcuprog
+ * See https://github.com/microchip-pic-avr-tools/pymcuprog
+ */
+
+#ifndef updi_state_h
+#define updi_state_h
+
+#include "libavrdude.h"
+
+typedef enum
+{
+  UPDI_LINK_MODE_16BIT,
+  UPDI_LINK_MODE_24BIT
+} updi_datalink_mode;
+
+typedef enum
+{
+  UPDI_NVM_MODE_V0,
+  UPDI_NVM_MODE_V2,
+  UPDI_NVM_MODE_V3
+} updi_nvm_mode;
+
+#define SIB_INFO_STRING_LENGTH 32
+#define SIB_INFO_FAMILY_LENGTH 8
+#define SIB_INFO_NVM_LENGTH    3
+#define SIB_INFO_DEBUG_LENGTH  3
+#define SIB_INFO_PDI_LENGTH    4
+#define SIB_INFO_EXTRA_LENGTH  20
+
+typedef struct 
+{
+  unsigned char sib_string[SIB_INFO_STRING_LENGTH+1];
+  char family_string[SIB_INFO_FAMILY_LENGTH+1];
+  char nvm_string[SIB_INFO_NVM_LENGTH+1];
+  char debug_string[SIB_INFO_DEBUG_LENGTH+1];
+  char pdi_string[SIB_INFO_PDI_LENGTH+1];
+  char extra_string[SIB_INFO_EXTRA_LENGTH+1];
+  char nvm_version;
+  char debug_version;
+} updi_sib_info;
+
+typedef struct
+{
+  updi_sib_info sib_info;
+  updi_datalink_mode datalink_mode;
+  updi_nvm_mode nvm_mode;
+} updi_state;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+updi_sib_info* updi_get_sib_info(PROGRAMMER * pgm);
+updi_datalink_mode updi_get_datalink_mode(PROGRAMMER * pgm);
+void updi_set_datalink_mode(PROGRAMMER * pgm, updi_datalink_mode mode);
+updi_nvm_mode updi_get_nvm_mode(PROGRAMMER * pgm);
+void updi_set_nvm_mode(PROGRAMMER * pgm, updi_nvm_mode mode);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* updi_state_h */
diff --git a/pgm_type.c b/pgm_type.c
index 9f28f441..becf7bdd 100644
--- a/pgm_type.c
+++ b/pgm_type.c
@@ -45,6 +45,7 @@
 #include "pickit2.h"
 #include "ppi.h"
 #include "serbb.h"
+#include "serialupdi.h"
 #include "stk500.h"
 #include "stk500generic.h"
 #include "stk500v2.h"
@@ -87,6 +88,7 @@ const PROGRAMMER_TYPE programmers_types[] = {
         {"par", par_initpgm, par_desc},
         {"pickit2", pickit2_initpgm, pickit2_desc},
         {"serbb", serbb_initpgm, serbb_desc},
+        {"serialupdi", serialupdi_initpgm, serialupdi_desc},
         {"stk500", stk500_initpgm, stk500_desc},
         {"stk500generic", stk500generic_initpgm, stk500generic_desc},
         {"stk500v2", stk500v2_initpgm, stk500v2_desc},