pwm.c

   1
   2 #include "pwm.h"
   3
   4 //The PWM has no loop function. It runs entirely out of the ISR.
   5 void pwm_loop(){}
   6
   7 #ifdef HAS_PWM_SUPPORT
   8
   9 void pwm_setup(){
  10     //s/w "BCM"(<== "Binary Code Modulation") timer setup
  11     TCCR0A |= _BV(WGM00)|_BV(WGM01);
  12     TCCR0B |= _BV(CS02);
  13     TIMSK0 |= _BV(TOIE0);
  14     //FIXME set PWM output DDRs
  15 }
  16
  17 //Software PWM stuff
  18 //Called every 256 cpu clks (i.e should not get overly long)
  19 ISR(TIMER0_OVF_vect){
  20     uint8_t Q = 0;
  21     Q |= (pwm_val[0] & pwm_cycle);
  22     Q |= (pwm_val[1] & pwm_cycle)?2:0;
  23     Q |= (pwm_val[2] & pwm_cycle)?4:0;
  24     Q |= (pwm_val[3] & pwm_cycle)?8:0;
  25     Q |= (pwm_val[4] & pwm_cycle)?16:0;
  26     PORTC = Q;
  27     OCR0A = pwm_cycle;
  28     pwm_cycle<<=1;
  29     if(!pwm_cycle){
  30         pwm_cycle = 1;
  31     }
  32 }
  33
  34 uint8_t pwm_cycle = 0;
  35 uint8_t pwm_val[PWM_COUNT];
  36
  37 #else//HAS_PWM_SUPPORT
  38
  39 void pwm_setup(){}
  40
  41 #endif//HAS_PWM_SUPPORT