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(WGM01);
  13     TCCR0B |= _BV(CS02);
  14     TIMSK0 |= _BV(OCIE0A);
  15     OCR0A = 1;
  16     pwm_output_setup();
  17 }
  18
  19 ISR(TIMER0_COMPA_vect){
  20     pwm_unset_outputs();
  21     pwm_cycle<<=1;
  22     if(!pwm_cycle){
  23         pwm_cycle = 1;
  24     }
  25     uint8_t Q = 0;
  26     Q |= (pwm_val[0] & pwm_cycle)?1:0;
  27     Q |= (pwm_val[1] & pwm_cycle)?2:0;
  28     Q |= (pwm_val[2] & pwm_cycle)?4:0;
  29     Q |= (pwm_val[3] & pwm_cycle)?8:0;
  30     Q |= (pwm_val[4] & pwm_cycle)?16:0;
  31     Q |= (pwm_val[5] & pwm_cycle)?32:0;
  32     Q |= (pwm_val[6] & pwm_cycle)?64:0;
  33     Q |= (pwm_val[7] & pwm_cycle)?128:0;
  34     pwm_set_outputs(Q);
  35     TCNT0 = 0;
  36     OCR0A = pwm_cycle;
  37 }
  38
  39 uint8_t pwm_cycle = 1;
  40 uint8_t pwm_val[8];
  41
  42 #else//HAS_PWM_SUPPORT
  43
  44 void pwm_setup(){}
  45
  46 #endif//HAS_PWM_SUPPORT