<snipped>
>>// main loop
>>while(1)
>>{
>>//if(bit_is_set(UCSRA,RXC)) outp(inp(UDR),UDR); // read in character
>>cmd();
>>}
>>
>>return 0;
>>}
>>
>>void cmd(void)
>>{
>>if(bit_is_set(UCSRA,RXC)) outp(inp(UDR),UDR); // read in character
>>}
>>
If you take a look at the outp and inp macros in iomacros.h, you'll
notice that they're pretty gnarly. Try unnesting the calls:
void cmd(void)
{
volatile unsigned char ch;
if(bit_is_set(UCSRA,RXC))
{
ch = inp(UDR);
outp(ch, UDR);
}
return;
}
This code is untested; however, with convoluted macros such as those,
it is always best to use them in the most simplest manner. I put in
the volatile just in case the optimizer decided to do something flaky
with the variable.
I downloaded the Beta 2 version of AVR GCC for the ATmega128 which
includes an optional set of new headers to allow direct assignment to
the registers instead of the inp() and outp() macros. These headers
are great! This is the standard way to access registers on practically
all other compilers and I'm surprised that they weren't done this way
until now (I'm relatively new to the GCC compiler, but have been doing
embedded software for over 7 years).
HTH,
Eric Weddington
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