[avr-gcc-list] Compiler macros and how to define them?

[Alexander Rice]

Hi all,

I'm just starting out with AVR micro controllers and the avr-gcc 
toolchain in the form of WinAVR.

As an exercise I thought I'd try defining my own function for setting up 
the hardware timers. In a header file I have:

------------

//Timer prescaler definitions
enum{   STOP = 0,
            CLK1 = 1;
            CLK8 = 2;
            CLK32 = 3;
            etc. } __clocksource;


void timer1_clocksource (int __clocksource)
//put the value from the prescaler definition into timer 1's SFR
{
      TCCR1B |=  __clocksource;
}
-----------

This works, however a look at the .lst file seems to suggest that 
'clocksource' and the function 'timer1_clocksource' are actually defined 
in the compiled code.

My question is: what must I do to ensure that the the variable 
'__clocksource' behaves like a #define statement and the function 
'timer1_clocksource' is inlined?

Also, from looking at the math.h library routines I have gathered that 
the convention seems to be to use two underscore characters for 
variables defined in header files. Are there any other conventions I 
should be aware of; or better, a coding style guide for header files?

Setting up timers is a common and somewhat laborious task requiring 
repeated reference to the datasheet, it would be nice to have a library 
routine that made things easier. By wrapping some functions similar to 
the above in some #if defined (__AVR_ATmega32__) etc. statements to deal 
with specific devices it would seem to be fairly simple, so simple in 
fact that if I got it working nicely I could contribute it back to the 
project.

Regards

Alex