#23 program fuse bits through avr-gdb, avarice and debugwire

[sep]

Hey,

there exist a problem with avarice with the program loading within the avr-gdb.
If there are fuse bits defined in the source code, then it is not possible to load the program with avr-gdb.
Here is a short example code

#include <avr/io.h>

FUSES =
{
    .low = FUSE_CKSEL0 & FUSE_SUT1,
    .high = FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN,
    .extended = FUSE_BODLEVEL0 & FUSE_HWBE,
};

int __attribute__((OS_main)) main( void ) {
    while(1);
    return 0;
}

I compiled this with:

avr-gcc -mmcu=atmega32u2 -O0 -g -o firmware.elf main.c

For the ATmega32U2. Debugwire is enabled.
For debugging I use a Atmel JTAGICE mkII. To use avarice with th ATmega32U2 I used this patch.
I've started avarice with:

$ avarice -2 -P atmega32u2 -w -j usb -C :4242 -d

and avr-gdb:

$ avr-gdb firmware.elf 
GNU gdb (Gentoo 7.11 vanilla) 7.11
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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and "show warranty" for details.
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Type "show configuration" for configuration details.
For bug reporting instructions, please see:
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For help, type "help".
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Reading symbols from firmware.elf...done.
(gdb) target remote :4242
Remote debugging using :4242
main () at main.c:11
11          while(1);
(gdb) load
Loading section .fuse, size 0x3 lma 0x820000
Load failed
(gdb) quit
A debugging session is active.

        Inferior 1 [Remote target] will be killed.

Quit anyway? (y or n) y

The avarice log file is attached.

Greetings sep

[Jes Bodi Klinke]

The DebugWire protocol does not support setting fuses, you will have to use ISP (or high-voltage programming) load such a program - at least initially.

Regards
Jes

[Joerg Wunsch]

The DebugWire protocol does not support setting fuses

That's not the point. The point is that attempt to program fuses should be silently discarded, so GDB will proceed.