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 static uint16_t pwm[N_PWMLEDS];
   8 static volatile unsigned char step;
   9
  10 void init_pwm()
  11 {
  12         int i;
  13
  14         step = 0;
  15
  16         for (i = 0; i < N_PWMLEDS; i++)
  17                 pwm[n] = 0;
  18
  19         /* Async clock */
  20         PLLCSR = _BV(PLLE);
  21
  22         /* Synchronize to the phase lock */
  23         _delay_ms(1);
  24         while ((PLLCSR & _BV(PLOCK)) == 0)
  25                 ;
  26         PLLCSR |= _BV(PCKE);
  27
  28         // PWM channel D is inverted, ...
  29         TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
  30         // PWM channels A and B are not
  31         TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(PWM1A) | _BV(PWM1B);
  32         TCCR1D = 0;
  33         TCCR1B = _BV(CS10);                     // no clock prescaling
  34
  35         TC1H = PWM_MAX >> 8;
  36         OCR1C = PWM_MAX & 0xFF;                         // TOP value
  37
  38         TC1H = PWM_MAX >> 8;            // PWM3 is inverted
  39         OCR1D = PWM_MAX & 0xFF;
  40
  41         TC1H = 0x00;
  42         OCR1B = OCR1A = 0;              // initial stride is 0
  43
  44         DDRB  &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // tristate it
  45         PORTB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // set to zero
  46 }
  47
  48 void susp_pwm()
  49 {
  50         unsigned char i;
  51
  52         for (i = 0; i < N_PWMLEDS; i++)
  53                 pwm[i] = 0;
  54
  55         DDRB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 ));
  56         TCCR1D = TCCR1C = TCCR1B = TCCR1A = 0;
  57         TIMSK = 0;
  58         TIFR = 0;
  59 }
  60
  61 void pwm_off(unsigned char n)
  62 {
  63         pwm[n] = 0;
  64
  65         switch (n) {
  66         case 0: DDRB &= ~_BV(PB1); break;
  67         case 1: DDRB &= ~_BV(PB3); break;
  68         case 2: DDRB &= ~_BV(PB5); break;
  69         }
  70 }
  71
  72 static void pwm_update_hw(unsigned char n)
  73 {
  74         unsigned char hi, lo;
  75         uint16_t stride = (pwm[n] + step) >> PWM_STEP_SHIFT;
  76
  77         if (n == 2)
  78                 stride = PWM_MAX - stride;
  79
  80         hi = stride >> 8;
  81         lo = stride & 0xFF;
  82
  83         switch (n) {
  84         case 0:
  85                 TC1H = hi;
  86                 OCR1A = lo;
  87                 DDRB |= _BV(PB1);
  88                 break;
  89         case 1:
  90                 TC1H = hi;
  91                 OCR1B = lo;
  92                 DDRB |= _BV(PB3);
  93                 break;
  94         case 2:
  95                 TC1H = hi;
  96                 OCR1D = lo;
  97                 DDRB |= _BV(PB5);
  98                 break;
  99         }
 100 }
 101
 102 void pwm_set(unsigned char n, uint16_t stride)
 103 {
 104         if (((stride + (1 << PWM_STEP_SHIFT)) >> PWM_STEP_SHIFT) >= PWM_MAX)
 105                 stride = PWM_MAX << PWM_STEP_SHIFT;
 106
 107         pwm[n] = stride;
 108         pwm_update_hw(n);
 109 }
 110
 111 void pwm_timer()
 112 {
 113         unsigned char i;
 114
 115         if (++step >= (1 << PWM_STEP_SHIFT))
 116                 step = 0;
 117
 118         for (i = 0; i < N_PWMLEDS; i++)
 119                 if (pwm[n])
 120                         pwm_update_hw(n);
 121 }
 122
 123 #if 0
 124 static void inline pwm_handler()
 125 {
 126         OCR1A = pwmval[0];
 127         OCR1B = pwmval[1];
 128         OCR1D = pwmval[2];
 129         TIMSK &= ~_BV(TOIE1);
 130 }
 131
 132 ISR(TIMER1_OVF_vect)
 133 {
 134         pwm_handler();
 135 }
 136 #endif
 137