Re: [avr-chat] Strange struct problem

[Ian Caddy]

Hi Daniel,

Your problem is that you need to also include your initialised data 
section in your hex file.  The initialised data will be copied to your 
data section by the startup code, but only if you include it in your hex 
file which you are not.

> avr-objcopy -j .text -O ihex testcase.elf testcase.hex

You are only including the .text section.

Because of this, the initilised data section is empty (0xFF) and these 
values are copied to the data section on startup.

> avr-objcopy -O ihex testcase.elf testcase.hex

should work for you as it will copy the sections that it thinks it 
should rather than you telling it to just use the .text section with the 
-j field.

I hope this helps,

Ian Caddy


Daniel O'Connor wrote:
> On Fri, 9 Dec 2005 14:49, Larry Barello wrote:
>
> > Which version of the compiler are you using?  I find it hard to believe
> > that something this fundamental (a static array of five chars) would go
> > unnoticed until now.
>
>
> Yeah, me too :)
> The .lst file shows buffer and abc are in the data section..
>
> The data section ends up in SRAM, right?
>
>
> > I took your test case, stripped it down and it appears that GCC does the
> > right thing: Because the data is initialized it sticks the struct onto the
> > stack then initializes the values.
> >
> > The version of GCC I am using is 3.4.3 (WinAvr)
>
>
> [inchoate 15:11] ~ >avr-gcc -v
> Reading specs from /usr/local/lib/gcc/avr/3.4.4/specs
> Configured with: ./configure --target=avr --disable-nls --prefix=/usr/local 
> i386-portbld-freebsd7.0
> Thread model: single
> gcc version 3.4.4
>
>
> > Are you using some hacked version of the C runtime, or startup that isn't
> > initializing the SRAM data?  Or is it possible you application is > 64k and
> > the initialized data segment is beyond the reach of the LPM command (IIRC
> > gcc can't access data > 64k, although the code can go that high)
>
>
> If you take my testcase.c file and do..
> avr-gcc -O2 -fno-strict-aliasing -pipe  -g -Wall -Wunreachable-code 
> -DF_CPU=16000000 -mmcu=atmega32 -Wa,-adhlmsn=testcase.lst -c testcase.c -o 
> testcase.o
> avr-gcc -O2 -fno-strict-aliasing -pipe  -g -Wall -Wunreachable-code -DF_CPU=16000000 -mmcu=atmega32  -Wl,-Map=testcase.map,--cref  -g testcase.o -o testcase.elf 
> avr-objcopy -j .text -O ihex testcase.elf testcase.hex
> avr-objdump -S testcase.elf > testcase.dmp
>
> You will get the code I am shoving into my micro, which I do with..
>
> avrdude -U flash:w:testcase.hex -p m32 -c alf -E vcc,noreset -q
>
>
>
>
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--
Ian Caddy
Goanna Technologies Pty Ltd
+61 8 9221 1860