common/timer.c

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