Re: [avr-gcc-list] ATMega16 interrupt vectors

[James Washer]

Just for fun, try adding the -mmcu=atmega16 to the link loader line as well.

On Sat, 10 Dec 2005 14:57:30 +0100
Henrik Brix Andersen <address@hidden> wrote:

> Hi,
> 
> I've stumbled across a problem using interrupts with the Atmel AVR
> Mega16(L). I have isolated a small test-case demonstrating the
> problem (attached).
> 
> The test case works as expected when compiled with the commercial
> Codevision AVR C compiler, but triggers the wrong ISR when compiled
> with avr-gcc. If I redefine the INT0_vect and INT1_vect values as
> shown at the top of the file, it triggers the correct ISRs. The odd
> thing is that the disassembly looks correct, at least to me.
> 
> The code should be self-explaining, but here's a small description of
> what I expect it to do: I enable external interrupts 0 and 1 which are
> both connected to push-buttons, and use them to alter the state of
> PORTB, which is connected to a row of LEDs.
>   * At system reset the PD7 LED is turned on.
>   * Pulling INT0 low should turn on the PD0 LED.
>   * Pulling INT1 low should turn on the PD1 LED.
> 
> That's how the program works when compiled with the Codevision AVR C
> compiler.
> 
> But this is what actually happens when compiled with avr-gcc:
>   * At system reset the PD7 LED is turned on (as expected).
>   * Pulling INT0 low turns on PD1 (INT1 ISR is executed?).
>   * Pulling INT1 low causes a system reset (or triggers
>     __vector_default if specfied).
> 
> 
> I've used the following software to test this:
> 
>   avr-libc-1.4.0
> 
>   $ avr-gcc --version
>   avr-gcc (GCC) 3.4.4 (Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)
> 
>   $ avr-objcopy --version
>   GNU objcopy 2.16.1
> 
>   The Codevision AVR C compiler used to verify this was version 1.24.6
>   Standard.
> 
> 
> These are the commands I used for compiling the test case with avr-gcc:
> 
>   $ avr-gcc -mmcu=atmega16 -Wall -c main.c
>   main.c: In function `main':
>   main.c:26: warning: large integer implicitly truncated to unsigned type
> 
>   $ avr-gcc -o interrupt-test.out main.o
> 
>   $ avr-objcopy -j .text -j .data -O ihex interrupt-test.out 
> interrupt-test.hex
> 
> 
> The resulting interrupt-test.hex file was written to the AVR using
> avrdude-5.0 and an STK500v2 programmer:
> 
>   $ avrdude -c stk500v2 -p atmega16 -P /dev/ttyUSB0 -e -U 
> flash:w:interrupt-test.hex
> 
> 
> The disassembly (attached) was produced like this:
> 
>   $ avr-objdump -S interrupt-test.out > interrupt-test.s
> 
> 
> Can someone explain the cause of this?
> 
> Regards,
> Brix
> 
> PS: I hope this is the correct mailing list for this kind of questions
> - couldn't find the difference between this list and the avr-libc-dev
> list?
> -- 
> Henrik Brix Andersen <address@hidden>
> Gentoo Metadistribution | Mobile computing herd
>