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bootloader not erasing all usable flash on atmega2560 #7

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ellensp opened this issue Apr 19, 2020 · 0 comments · May be fixed by arduino/Arduino-stk500v2-bootloader#2
Open

bootloader not erasing all usable flash on atmega2560 #7

ellensp opened this issue Apr 19, 2020 · 0 comments · May be fixed by arduino/Arduino-stk500v2-bootloader#2

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@ellensp
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ellensp commented Apr 19, 2020 •
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On a atmega2560 the usable flash is meant to be 256k-8k bootloader. Ie 0-0x3E000 (253952 bytes.) but in the code is

#if FLASHEND > 0x0F000
	#define BOOTSIZE 8192
#else
	#define BOOTSIZE 2048
#endif

#define APP_END  (FLASHEND -(2*BOOTSIZE) + 1)

FLASHEND is 0x3FFFF on mega2560's so the the BOOTSIZE is set to 8192, but the APP_END is set to (0x3FFFF - (2*0x2000)) + 1 = 0x3C000

The code then uses "if (eraseAddress < APP_END )" so uploading over serial will only erase bytes from 0x00000 to 0x3C000. So 0x3C000--0x3E000 is not erased and can't be reused till a full erase is done.

This has been causing headaches for years.
@ellensp ellensp mentioned this issue Apr 20, 2020
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@ellensp ellensp mentioned this issue Feb 15, 2022
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Ancyker added a commit to Ancyker/Arduino-stk500v2-bootloader that referenced this issue Dec 1, 2022
@Ancyker
Fix mega2560 erase flash error
31f6fa0 
Fixes msproul#7 and makes code compatible with avr-gcc.

Hex file compiled with avr-gcc 11.2.0 on FreeBSD.
Ancyker added a commit to Ancyker/Arduino-stk500v2-bootloader that referenced this issue Dec 1, 2022
@Ancyker
Fix mega2560 erase flash error
76b6515 
Fixes msproul#7 and makes code compatible with avr-gcc.

Hex file compiled with avr-gcc 11.2.0 on FreeBSD.
@Ancyker Ancyker linked a pull request Dec 1, 2022 that will close this issue
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This was referenced Jun 10, 2023
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Fix mega2560 erase flash error Ancyker/Arduino-stk500v2-bootloader
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@ellensp