patch #9328: ft245r.c: add TPI support (patches 5-7)

Submitted by David Mosberger-Tang:
* ft245r.c (ft245r_set_bitclock): add workaround for
FT245 hardware bugs in bitclock setting

Correct baud rate calculation (multiplying with factor of 2 was wrong)
and add compile-time workaround for FTDI chips suffering for the
variable pulse-width errata.  The workaround entails always running
the chip at 3MHz and stuffing the channel with repeated bytes to
achieve the desired baudrate.

This has no effect on programming speed.  Note, however, that now a
baudrate option -b750000 has to be used to achieve maximum speed.

(Option enabled by default now.)



git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@1488 81a1dc3b-b13d-400b-aceb-764788c761c2

ft245r.c

@@ -59,6 +59,7 @@
 #include <sys/time.h>
 #include <unistd.h>
 #include <stdint.h>
+#include <math.h>
 
 #include "avrdude.h"
 #include "libavrdude.h"
@@ -113,9 +114,26 @@ void ft245r_initpgm(PROGRAMMER * pgm) {
 //#define USE_INLINE_WRITE_PAGE
 
 #define FT245R_DEBUG	0
+/*
+  Some revisions of the FTDI chips mess up the timing in bitbang mode
+  unless the bitclock is set to the max (3MHz).  For example, see:
+
+  http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_120_FT232R%20Errata%20Technical%20Note.pdf
+
+  To work around this problem, set the macro below to 1 to always set
+  the bitclock to 3MHz and then issue the same byte repeatedly to get
+  the desired timing.
+
+*/
+#define FT245R_BITBANG_VARIABLE_PULSE_WIDTH_WORKAROUND 1
 
 static struct ftdi_context *handle;
 
+#if FT245R_BITBANG_VARIABLE_PULSE_WIDTH_WORKAROUND
+static unsigned int baud_multiplier;
+#else
+# define baud_multiplier 1		// this let's C compiler optimize
+#endif
 static unsigned char ft245r_ddr;
 static unsigned char ft245r_out;
 
@@ -213,14 +231,16 @@ static int ft245r_flush(PROGRAMMER * pgm) {
 
 static int ft245r_send2(PROGRAMMER * pgm, unsigned char * buf, size_t len,
 			bool discard_rx_data) {
-    int i;
+    int i, j;
 
     for (i = 0; i < len; ++i) {
-	if (discard_rx_data)
-	    ++rx.discard;
-	tx.buf[tx.len++] = buf[i];
-	if (tx.len >= FT245R_MIN_FIFO_SIZE)
-	    ft245r_flush(pgm);
+	for (j = 0; j < baud_multiplier; ++j) {
+	    if (discard_rx_data)
+		++rx.discard;
+	    tx.buf[tx.len++] = buf[i];
+	    if (tx.len >= FT245R_MIN_FIFO_SIZE)
+		ft245r_flush(pgm);
+	}
     }
     return 0;
 }
@@ -235,7 +255,7 @@ static int ft245r_send_and_discard(PROGRAMMER * pgm, unsigned char * buf,
 }
 
 static int ft245r_recv(PROGRAMMER * pgm, unsigned char * buf, size_t len) {
-    int i;
+    int i, j;
 
     ft245r_flush(pgm);
     ft245r_fill(pgm);
@@ -249,8 +269,11 @@ static int ft245r_recv(PROGRAMMER * pgm, unsigned char * buf, size_t len) {
 	--rx.discard;
     }
 
-    for (i = 0; i < len; ++i)
+    for (i = 0; i < len; ++i) {
 	buf[i] = ft245r_rx_buf_get(pgm);
+	for (j = 1; j < baud_multiplier; ++j)
+	    ft245r_rx_buf_get(pgm);
+    }
     return 0;
 }
 
@@ -298,23 +321,32 @@ static int ft245r_chip_erase(PROGRAMMER * pgm, AVRPART * p) {
 
 
 static int ft245r_set_bitclock(PROGRAMMER * pgm) {
-    int r;
-    int rate = 0;
+    // libftdi1 multiplies bitbang baudrate by 4:
+    int r, rate = 0, ftdi_rate = 3000000 / 4;
 
     /* bitclock is second. 1us = 0.000001. Max rate for ft232r 750000 */
     if(pgm->bitclock) {
-        rate = (uint32_t)(1.0/pgm->bitclock) * FT245R_CYCLES;
+        rate = (uint32_t)(1.0/pgm->bitclock);
     } else if (pgm->baudrate) {
-        rate = pgm->baudrate * FT245R_CYCLES;
+        rate = pgm->baudrate;
     } else {
         rate = 150000; /* should work for all ftdi chips and the avr default internal clock of 1MHz */
     }
 
-    if (FT245R_DEBUG) {
-        avrdude_message(MSG_NOTICE2, " ft245r:  spi bitclk %d -> ft baudrate %d\n",
-                rate / FT245R_CYCLES, rate);
-    }
-    r = ftdi_set_baudrate(handle, rate);
+#if FT245R_BITBANG_VARIABLE_PULSE_WIDTH_WORKAROUND
+    if (rate > 0 && rate < ftdi_rate)
+	baud_multiplier = round((ftdi_rate + rate - 1) / rate);
+    else
+	baud_multiplier = 1;
+#else
+    ftdi_rate = rate;
+#endif
+
+    avrdude_message(MSG_NOTICE2,
+		    "%s: bitclk %d -> FTDI rate %d, baud multiplier %d\n",
+		    __func__, rate, ftdi_rate, baud_multiplier);
+
+    r = ftdi_set_baudrate(handle, ftdi_rate);
     if (r) {
         avrdude_message(MSG_INFO, "Set baudrate (%d) failed with error '%s'.\n",
                 rate, ftdi_get_error_string (handle));