firmware/pwm.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <util/delay.h>
   4
   5 #include "lights.h"
   6
   7 #define PWM_MAX 0x0FF
   8
   9 void init_pwm()
  10 {
  11         /* Async clock */
  12         PLLCSR = _BV(PLLE);
  13
  14         /* Synchronize to the phase lock */
  15         _delay_ms(1);
  16         while ((PLLCSR & _BV(PLOCK)) == 0)
  17                 ;
  18         PLLCSR |= _BV(PCKE);
  19
  20         // PWM channel D is inverted, ...
  21         TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
  22         // PWM channels A and B are not
  23         TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(PWM1A) | _BV(PWM1B);
  24         TCCR1D = 0;
  25         TCCR1B = _BV(CS10);                     // no clock prescaling
  26         TC1H = PWM_MAX >> 8;
  27         OCR1C = PWM_MAX & 0xFF;                         // TOP value
  28
  29         TC1H = PWM_MAX >> 8;
  30         OCR1D = PWM_MAX & 0xFF;
  31
  32         TC1H = 0x00;
  33         OCR1B = OCR1A = 0;              // initial stride is 0
  34
  35         DDRB  &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // tristate it
  36         PORTB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // set to zero
  37 }
  38
  39 void pwm_off(unsigned char n)
  40 {
  41         switch (n) {
  42         case 0: DDRB &= ~_BV(PB1); break;
  43         case 1: DDRB &= ~_BV(PB3); break;
  44         case 2: DDRB &= ~_BV(PB5); break;
  45         }
  46 }
  47
  48 void pwm_set(unsigned char n, unsigned char stride)
  49 {
  50         TC1H = 0x00;
  51         switch (n) {
  52         case 0:
  53                 OCR1A = stride;
  54                 DDRB |= _BV(PB1);
  55                 break;
  56         case 1: OCR1B = stride;
  57                 DDRB |= _BV(PB3);
  58                 break;
  59         case 2: {
  60                         uint16_t s16 = PWM_MAX - (uint16_t)stride;
  61                         volatile unsigned char hi, lo;
  62                         hi = s16 >> 8;
  63                         lo = s16 & 0xFF;
  64                         TC1H = hi;
  65                         OCR1D = lo;
  66                         DDRB |= _BV(PB5);
  67                 }
  68                 break;
  69         }
  70 }
  71
  72 #if 0
  73 static void inline pwm_handler()
  74 {
  75         OCR1A = pwmval[0];
  76         OCR1B = pwmval[1];
  77         OCR1D = pwmval[2];
  78         TIMSK &= ~_BV(TOIE1);
  79 }
  80
  81 ISR(TIMER1_OVF_vect)
  82 {
  83         pwm_handler();
  84 }
  85 #endif
  86