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