Re: [avr-gcc-list] problems with timer0 on atmega128

[Volkmar Dierkes]

Josh,

I tried to simulate your example in VMLAB and I can't find any 
problem which results in that way as you describe. I get the 
behavior as you want to have.

Only some hints. I am not sure which gcc version you use, but I 
changed the #include-section to this:
#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>

You should not include an avr/ioxxx.h file. It is recommend to use 
avr/io.h. The correct MCU is declared via the makefile. Oh, I see I 
used a makefile which I took from another project. Maybe there is a 
difference, but I have only less experience on the options to 
avr-gcc. Here is what my makefile does:

avr-gcc -c -g -Os -funsigned-char -funsigned-bitfields -fpack-struct 
-fshort-enums -Wall -Wstrict-prototypes -Wa,-ahlms=tmr_test.lst -mmcu=atmega128 
-I. tmr_test.c -o tmr_test.o
tmr_test.c:20: warning: function declaration isn't a prototype
tmr_test.c:43:2: warning: no newline at end of file
avr-gcc -Wl,-Map=tmr_test.map,--cref -mmcu=atmega128 tmr_test.o -lm --output 
tmr_test.elf
avr-objcopy -O ihex -R .eeprom tmr_test.elf tmr_test.hex
avr-objcopy -j .eeprom --set-section-flags=.eeprom="alloc,load" 
--change-section-lma .eeprom=0 -O ihex tmr_test.elf tmr_test.eep
avr-objdump -h -S tmr_test.elf > tmr_test.lss

And also, it is recommend to use
    TCCR0 = 5;            // set timer0 prescaler
    OCR0  = 0xff;         // set compare0 to 0xff
    TIMSK |= _BV(OCIE0);  // interrupt on compare
    TIMSK &= ~_BVOCIE0);
instead of the outp(), sbi(), cbi() stuff.

Volkmar


On Wed, 29 Jan 2003 19:46:36 -0500, Josh Thompson wrote:

> Hi,
>
> I am trying to figure out how to use a timer to run code while my main
> program loop is doing something else.  I have 2 LEDs connected to an
> atmega128, one to PORTD, the other to PORTA.  When running the attached
> code, I would expect this to happen:
>
>
>
> at start, LED on PORTA should be on steady
> LED on PORTD should be flashing rapidly
>
> after some amount of time,
> LED on PORTA should go off and
> LED on PORTD should be flashing slower
>
>
>
>
> All that happens is that LED on PORTA comes on.
>
> Here is how I'm compiling it:
>
> avr-gcc -mmcu=atmega128 main.c -o main
>
> Thanks for your help; this is driving me crazy!!
> Josh
>
>
> ---------------------------------------------------
> #include <avr/iom128.h>
> #include <sig-avr.h>
> #include <interrupt.h>
> #include <io.h>
>
> #define TIMERCOUNTER_PERIODIC_TIMEOUT 100
>
> volatile static unsigned char timerCounter;
>
> void initTimer(void) {
>    outb(TCCR0, 5);        // set timer0 prescaler
>    outb(OCR0, 0xff);       // set compare0 to 0xff
>    sbi(TIMSK, OCIE0);    // interrupt on compare
>    timerCounter = 0;
> }
>
> SIGNAL(SIG_OUTPUT_COMPARE0) {
>    timerCounter++;
> }
>
> int main() {
>    volatile static unsigned int count;
>    volatile static unsigned int max;
>
>    DDRD = 0xff;    PORTD = 0X00;
>    DDRA = 0xff;    PORTA = 0x01;
>
>    max = 1000;
>    sei();
>    initTimer();
>
>    for(;;) {
>       PORTD = 0x60;
>       for(count = 0; count < max; count++);
>       PORTD = 0x00;
>       for(count = 0; count < max; count++);
>
>       if (timerCounter > TIMERCOUNTER_PERIODIC_TIMEOUT) {
>          cbi(TIMSK, OCIE0);
>          PORTA = 0x00;
>          max = 5000;
>       }
>    }
> }
> avr-gcc-list at http://avr1.org
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