pwm.c

   1
   2 #include "pwm.h"
   3 #include "led.h"
   4
   5 //The PWM has no loop function. It runs entirely out of the ISR.
   6 void pwm_loop(){}
   7
   8 #ifdef HAS_PWM_SUPPORT
   9
  10 void pwm_setup(){
  11     //s/w "BCM"(<== "Binary Code Modulation") timer setup
  12     TCCR0A |= _BV(WGM00)|_BV(WGM01);
  13     TCCR0B |= _BV(CS01)|_BV(CS00)|_BV(WGM02);
  14     TIMSK0 |= _BV(TOIE0);
  15     OCR0A = 1;
  16     pwm_output_setup();
  17     //FIXME debug stuff
  18     DDRB |= 0x20;
  19 }
  20
  21 //Software PWM stuff
  22 //Called every 256 cpu clks (i.e should not get overly long)
  23 ISR(TIMER0_OVF_vect){
  24     pwm_cycle<<=1;
  25     if(!pwm_cycle){
  26         pwm_cycle = 1;
  27     }
  28     uint8_t Q = 0;
  29     if(pwm_cycle&0x80)
  30         PORTB ^= 0x20;
  31     pwm_unset_outputs();
  32     Q |= !!(pwm_val[0] & pwm_cycle);
  33     Q |= (pwm_val[1] & pwm_cycle)?2:0;
  34     Q |= (pwm_val[2] & pwm_cycle)?4:0;
  35     Q |= (pwm_val[3] & pwm_cycle)?8:0;
  36     /*Q |= (pwm_val[4] & pwm_cycle)?16:0;
  37     Q |= (pwm_val[5] & pwm_cycle)?32:0;
  38     Q |= (pwm_val[6] & pwm_cycle)?64:0;
  39     Q |= (pwm_val[7] & pwm_cycle)?128:0;
  40     */
  41     pwm_set_outputs(Q);
  42     OCR0A = pwm_cycle;
  43 }
  44
  45 uint8_t pwm_cycle = 1;
  46 uint8_t pwm_val[8];
  47
  48 #else//HAS_PWM_SUPPORT
  49
  50 void pwm_setup(){}
  51
  52 #endif//HAS_PWM_SUPPORT