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 susp_pwm()
  41 {
  42         DDRB &= ~(_BV( PB1 ) | _BV( PB3 ) | _BV( PB5 ));
  43         TCCR1D = TCCR1C = TCCR1B = TCCR1A = 0;
  44         TIMSK = 0;
  45         TIFR = 0;
  46 }
  47
  48 void pwm_off(unsigned char n)
  49 {
  50         switch (n) {
  51         case 0: DDRB &= ~_BV(PB1); break;
  52         case 1: DDRB &= ~_BV(PB3); break;
  53         case 2: DDRB &= ~_BV(PB5); break;
  54         }
  55 }
  56
  57 void pwm_set(unsigned char n, uint16_t stride)
  58 {
  59         unsigned char hi, lo;
  60
  61         if (stride > PWM_MAX)
  62                 stride = PWM_MAX;
  63
  64         if (n == 2)
  65                 stride = PWM_MAX - stride;
  66
  67         hi = stride >> 8;
  68         lo = stride & 0xFF;
  69
  70         switch (n) {
  71         case 0:
  72                 TC1H = hi;
  73                 OCR1A = lo;
  74                 DDRB |= _BV(PB1);
  75                 break;
  76         case 1:
  77                 TC1H = hi;
  78                 OCR1B = lo;
  79                 DDRB |= _BV(PB3);
  80                 break;
  81         case 2:
  82                 TC1H = hi;
  83                 OCR1D = lo;
  84                 DDRB |= _BV(PB5);
  85                 break;
  86         }
  87 }
  88
  89 #if 0
  90 static void inline pwm_handler()
  91 {
  92         OCR1A = pwmval[0];
  93         OCR1B = pwmval[1];
  94         OCR1D = pwmval[2];
  95         TIMSK &= ~_BV(TOIE1);
  96 }
  97
  98 ISR(TIMER1_OVF_vect)
  99 {
 100         pwm_handler();
 101 }
 102 #endif
 103