firmware/timer.c

   1 /* $Id$
   2
   3 This file is part of the MSP Märklin suite
   4 Copyright © 2010  Mikkosoft Productions, Mikko Rasa
   5 Distributed under the GPL
   6 */
   7
   8 #include <avr/io.h>
   9 #include "timer.h"
  10
  11 #define BIT(n) (1<<(n))
  12
  13 static void timer_start(uint8_t num, uint32_t period)
  14 {
  15         uint8_t cs;
  16
  17         if(num==0)
  18         {
  19                 if(period<0x100)
  20                 {
  21                         cs = BIT(CS00);
  22                 }
  23                 else if(period<0x800)
  24                 {
  25                         cs = BIT(CS01);
  26                         period /= 8;
  27                 }
  28                 else if(period<0x4000)
  29                 {
  30                         cs = BIT(CS01) | BIT(CS00);
  31                         period /= 64;
  32                 }
  33                 else if(period<0x10000)
  34                 {
  35                         cs = BIT(CS02);
  36                         period /= 256;
  37                 }
  38                 else
  39                 {
  40                         cs = BIT(CS02) | BIT(CS00);
  41                         period /= 1024;
  42                         if(period>0xFF)
  43                                 period = 0xFF;
  44                 }
  45                 TCCR0A = BIT(WGM01);
  46                 TCCR0B = cs;
  47                 OCR0A = period;
  48                 TIMSK0 = BIT(OCIE0A);
  49         }
  50         if(num==1)
  51         {
  52                 if(period<0x10000)
  53                 {
  54                         cs = BIT(CS10);
  55                 }
  56                 else if(period<0x80000)
  57                 {
  58                         cs = BIT(CS11);
  59                         period /= 8;
  60                 }
  61                 else if(period<0x400000)
  62                 {
  63                         cs = BIT(CS11) | BIT(CS10);
  64                         period /= 64;
  65                 }
  66                 else if(period<0x1000000)
  67                 {
  68                         cs = BIT(CS12);
  69                         period /= 256;
  70                 }
  71                 else
  72                 {
  73                         cs = BIT(CS12) | BIT(CS10);
  74                         period /= 1024;
  75                         if(period>0xFFFF)
  76                                 period = 0xFFFF;
  77                 }
  78                 TCCR1A = 0;
  79                 TCCR1B = BIT(WGM12) | cs;
  80                 OCR1AH = period>>8;
  81                 OCR1AL = period;
  82                 TIMSK1 = BIT(OCIE1A);
  83         }
  84 }
  85
  86 void timer_start_hz(uint8_t num, uint32_t freq_p, uint8_t freq_q)
  87 {
  88         timer_start(num, F_CPU*freq_q/freq_p);
  89 }
  90
  91 void timer_start_us(uint8_t num, uint32_t us)
  92 {
  93         timer_start(num, F_CPU/1000000*us);
  94 }
  95
  96 void timer_stop(uint8_t num)
  97 {
  98         if(num==0)
  99         {
 100                 TCCR0B = 0;
 101                 TIMSK0 = 0;
 102         }
 103         else if(num==1)
 104         {
 105                 TCCR1B = 0;
 106                 TIMSK1 = 0;
 107         }
 108 }