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 0x1FF
   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
  27         TC1H = PWM_MAX >> 8;
  28         OCR1C = PWM_MAX & 0xFF;                         // TOP value
  29
  30         TC1H = PWM_MAX >> 8;            // PWM3 is inverted
  31         OCR1D = PWM_MAX & 0xFF;
  32
  33         TC1H = 0x00;
  34         OCR1B = OCR1A = 0;              // initial stride is 0
  35
  36         DDRB  &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // tristate it
  37         PORTB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // set to zero
  38 }
  39
  40 void pwm_off(unsigned char n)
  41 {
  42         switch (n) {
  43         case 0: DDRB &= ~_BV(PB1); break;
  44         case 1: DDRB &= ~_BV(PB3); break;
  45         case 2: DDRB &= ~_BV(PB5); break;
  46         }
  47 }
  48
  49 void pwm_set(unsigned char n, uint16_t stride)
  50 {
  51         unsigned char hi, lo;
  52
  53         if (stride > PWM_MAX)
  54                 stride = PWM_MAX;
  55
  56         if (n == 2)
  57                 stride = PWM_MAX - stride;
  58
  59         hi = stride >> 8;
  60         lo = stride & 0xFF;
  61
  62         switch (n) {
  63         case 0:
  64                 TC1H = hi;
  65                 OCR1A = lo;
  66                 DDRB |= _BV(PB1);
  67                 break;
  68         case 1:
  69                 TC1H = hi;
  70                 OCR1B = lo;
  71                 DDRB |= _BV(PB3);
  72                 break;
  73         case 2:
  74                 TC1H = hi;
  75                 OCR1D = lo;
  76                 DDRB |= _BV(PB5);
  77                 break;
  78         }
  79 }
  80
  81 #if 0
  82 static void inline pwm_handler()
  83 {
  84         OCR1A = pwmval[0];
  85         OCR1B = pwmval[1];
  86         OCR1D = pwmval[2];
  87         TIMSK &= ~_BV(TOIE1);
  88 }
  89
  90 ISR(TIMER1_OVF_vect)
  91 {
  92         pwm_handler();
  93 }
  94 #endif
  95