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 void init_pwm()
   8 {
   9         /* Async clock */
  10         PLLCSR = _BV(PLLE);
  11
  12         /* Synchronize to the phase lock */
  13         _delay_ms(1);
  14         while ((PLLCSR & _BV(PLOCK)) == 0)
  15                 ;
  16         PLLCSR |= _BV(PCKE);
  17
  18         // PWM channel D is inverted, ...
  19         TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
  20         // PWM channels A and B are not
  21         TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(PWM1A) | _BV(PWM1B);
  22         TCCR1D = 0;
  23         TCCR1B = _BV(CS10);                     // no clock prescaling
  24
  25         TC1H = PWM_MAX >> 8;
  26         OCR1C = PWM_MAX & 0xFF;                         // TOP value
  27
  28         TC1H = PWM_MAX >> 8;            // PWM3 is inverted
  29         OCR1D = PWM_MAX & 0xFF;
  30
  31         TC1H = 0x00;
  32         OCR1B = OCR1A = 0;              // initial stride is 0
  33
  34         DDRB  &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // tristate it
  35         PORTB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // set to zero
  36 }
  37
  38 void susp_pwm()
  39 {
  40         DDRB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 ));
  41         TCCR1D = TCCR1C = TCCR1B = TCCR1A = 0;
  42         TIMSK = 0;
  43         TIFR = 0;
  44 }
  45
  46 void pwm_off(unsigned char n)
  47 {
  48         switch (n) {
  49         case 0: DDRB &= ~_BV(PB1); break;
  50         case 1: DDRB &= ~_BV(PB3); break;
  51         case 2: DDRB &= ~_BV(PB5); break;
  52         }
  53 }
  54
  55 void pwm_set(unsigned char n, uint16_t stride)
  56 {
  57         unsigned char hi, lo;
  58
  59         if (stride > PWM_MAX)
  60                 stride = PWM_MAX;
  61
  62         if (n == 2)
  63                 stride = PWM_MAX - stride;
  64
  65         hi = stride >> 8;
  66         lo = stride & 0xFF;
  67
  68         switch (n) {
  69         case 0:
  70                 TC1H = hi;
  71                 OCR1A = lo;
  72                 DDRB |= _BV(PB1);
  73                 break;
  74         case 1:
  75                 TC1H = hi;
  76                 OCR1B = lo;
  77                 DDRB |= _BV(PB3);
  78                 break;
  79         case 2:
  80                 TC1H = hi;
  81                 OCR1D = lo;
  82                 DDRB |= _BV(PB5);
  83                 break;
  84         }
  85 }
  86
  87 #if 0
  88 static void inline pwm_handler()
  89 {
  90         OCR1A = pwmval[0];
  91         OCR1B = pwmval[1];
  92         OCR1D = pwmval[2];
  93         TIMSK &= ~_BV(TOIE1);
  94 }
  95
  96 ISR(TIMER1_OVF_vect)
  97 {
  98         pwm_handler();
  99 }
 100 #endif
 101