How can I access individual bytes of the union below in assembler?
volatile union {
uint32_t Counts;
uint16_t ints[2];
uint8_t bytes[4];
} foo
Can I just use lo8(foo), hi8(foo), hlo8(foo) and hhi8(hlo8)?
Sorry if I've put this topic in the wrong forum, but I've figured that as GAS is a part of GCC, and it involves mixing assembler and C, it should belong here.
Looks like i've got it, but when I try to compile the code below, the "teste" function is not linked (GCC gives a warning about an implicit declaration of 'teste').
Using AVR-Studio with WinAVR 20081205
the "get_key_short" function is from Danni's debounce code.
here is the main function
int main (void)
{
char Str_out[20];
DDRA = 0xFF;
PORTA = 0xF0;
OCR0 = F_CPU / 1024 * 10e-3;
// TMR0 CTC mode and divide 1024
TCCR0 = (1<<CS02)|(1<<CS00)|(1<<WGM01); // divide by 1024
TIMSK = 1<<OCIE0; // enable timer interrupt
LcdInitialize();
sei();
for(;;) {
if( get_key_short( 1<<KEY1 )) {
LcdClear();
teste();
ltoa(bar.Counts, Str_out, 10);
LcdPrintString(Str_out);
}
if( get_key_short( 1<<KEY2 )){
foo.Counts += 10;
foo.Counts *= -5;
LcdGotoXY(0,1);
ltoa(foo.Counts, Str_out, 10);
LcdPrintString(Str_out);
}
_delay_ms(250);
}
}
and here is the assembler function. It just copies foo to bar (both are defined as an union that is in the original post)
#include.extern foo .extern bar .global teste teste: lds r18, foo lds r19, foo+1 lds r20, foo+2 lds r21, foo+3 sts bar, r18 sts bar+1, r19 sts bar+2, r20 sts bar+3, r21 ret
Whats wrong with it?
Thank you,
rstahlhu 
I think you need to tell the main program about teste. Try extern in front of the function definition of teste.
I didn't do a foward declaration of teste in the first case. So I've tried with it now, and it's working!
Thank you rstahlhu.