firmware/pwm.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <util/delay.h>
   4 #include <util/atomic.h>
   5
   6 #include "lights.h"
   7
   8 static uint16_t pwm[N_PWMLEDS];
   9 static volatile unsigned char step;
  10
  11 static void enable_pll()
  12 {
  13         /* Async clock */
  14         PLLCSR = _BV(PLLE);
  15
  16         /* Synchronize to the phase lock */
  17         _delay_us(100);
  18         while ((PLLCSR & _BV(PLOCK)) == 0)
  19                 ;
  20         PLLCSR |= _BV(PCKE);
  21 }
  22
  23 void init_pwm()
  24 {
  25         int i;
  26
  27         step = 0;
  28
  29         for (i = 0; i < N_PWMLEDS; i++)
  30                 pwm[i] = 0;
  31
  32         enable_pll();
  33
  34         // PWM channel D is inverted, ...
  35         TCCR1C = _BV(COM1D1) | _BV(COM1D0) | _BV(PWM1D);
  36         // PWM channels A and B are not
  37         TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(PWM1A) | _BV(PWM1B);
  38         TCCR1D = 0;
  39         TCCR1B = _BV(CS10);                     // no clock prescaling
  40
  41         TC1H = PWM_MAX >> 8;
  42         OCR1C = PWM_MAX & 0xFF;                         // TOP value
  43
  44         TC1H = PWM_MAX >> 8;            // PWM3 is inverted
  45         OCR1D = PWM_MAX & 0xFF;
  46
  47         TC1H = 0x00;
  48         OCR1B = OCR1A = 0;              // initial stride is 0
  49
  50         DDRB  &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // tristate it
  51         PORTB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 )); // set to zero
  52 }
  53
  54 void susp_pwm()
  55 {
  56         unsigned char i;
  57
  58         for (i = 0; i < N_PWMLEDS; i++)
  59                 pwm[i] = 0;
  60
  61         DDRB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 ));
  62         TCCR1D = TCCR1C = TCCR1B = TCCR1A = 0;
  63         TIMSK = 0;
  64         TIFR = 0;
  65
  66         PLLCSR &= ~(_BV(PLLE) | _BV(PCKE));
  67 }
  68
  69 void pwm_off(unsigned char n)
  70 {
  71         ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
  72                 pwm[n] = 0;
  73
  74                 switch (n) {
  75                 case 0: DDRB &= ~_BV(PB1); break;
  76                 case 1: DDRB &= ~_BV(PB3); break;
  77                 case 2: DDRB &= ~_BV(PB5); break;
  78                 }
  79         }
  80 }
  81
  82 static void pwm_update_hw(unsigned char n)
  83 {
  84         unsigned char hi, lo;
  85         uint16_t stride = (pwm[n] + step) >> PWM_STEP_SHIFT;
  86
  87         if (n == 2)
  88                 stride = PWM_MAX - stride;
  89
  90         hi = stride >> 8;
  91         lo = stride & 0xFF;
  92
  93         switch (n) {
  94         case 0:
  95                 TC1H = hi;
  96                 OCR1A = lo;
  97                 break;
  98         case 1:
  99                 TC1H = hi;
 100                 OCR1B = lo;
 101                 break;
 102         case 2:
 103                 TC1H = hi;
 104                 OCR1D = lo;
 105                 break;
 106         }
 107 }
 108
 109 void pwm_set(unsigned char n, uint16_t stride)
 110 {
 111         if (((stride + (1 << PWM_STEP_SHIFT)) >> PWM_STEP_SHIFT) >= PWM_MAX)
 112                 stride = PWM_MAX << PWM_STEP_SHIFT;
 113
 114         ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 115                 pwm[n] = stride;
 116
 117                 pwm_update_hw(n);
 118
 119                 switch(n) {
 120                 case 0: DDRB |= _BV(PB1); break;
 121                 case 1: DDRB |= _BV(PB3); break;
 122                 case 2: DDRB |= _BV(PB5); break;
 123                 }
 124         }
 125 }
 126
 127 void pwm_timer()
 128 {
 129         unsigned char i;
 130
 131         if (++step >= (1 << PWM_STEP_SHIFT))
 132                 step = 0;
 133
 134         for (i = 0; i < N_PWMLEDS; i++)
 135                 if (pwm[i])
 136                         pwm_update_hw(i);
 137 }
 138