From fdcfb543fcaa3a8af2d3f2b8da4f6dc6d28cb0fe Mon Sep 17 00:00:00 2001
From: Stefan Rueger <stefan.rueger@urclocks.com>
Date: Wed, 4 Jan 2023 18:52:51 +0000
Subject: [PATCH] Improve guessBootloaderStart() for modern AVR

---
 src/avrcache.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/avrcache.c b/src/avrcache.c
index c7bfae3a..29f1d437 100644
--- a/src/avrcache.c
+++ b/src/avrcache.c
@@ -318,6 +318,9 @@ static int guessBootStart(const PROGRAMMER *pgm, const AVRPART *p) {
   int bootstart = 0;
   const AVR_Cache *cp = pgm->cp_flash;
 
+  if(p->prog_modes & PM_UPDI)   // Modern AVRs put the bootloader at 0
+    return 0;
+
   if(p->n_boot_sections > 0 && p->boot_section_size > 0)
     bootstart = cp->size - (p->boot_section_size<<(p->n_boot_sections-1));