avr/timer.c

   1 /*
   2  * (C) Copyright 2014 Leo C. <erbl259-lmu@yahoo.de>
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0
   5  */
   6
   7 #include "timer.h"
   8 #include <avr/interrupt.h>
   9 #include <util/atomic.h>
  10 #include "time.h"
  11
  12 /* timer interrupt/overflow counter */
  13 /* counts up every ms. */
  14 static volatile
  15 uint32_t timestamp;
  16
  17 /*
  18  * 1000Hz timer interrupt generated by OC4A
  19  */
  20 ISR(TIMER4_COMPA_vect)
  21 {
  22         static int_fast8_t tick_10ms;
  23         static int_fast8_t tick_1s;
  24         int_fast8_t i, j;
  25
  26         extern void disk_timerproc(void);
  27
  28         OCR4A += F_CPU / 1000;  /* 1000Hz interval */
  29
  30         timestamp++;
  31
  32         i = tick_10ms + 1;
  33         if (i == 10) {
  34                 Stat |= S_10MS_TO;
  35
  36                 /* Drive timer procedure of low level disk I/O module */
  37                 disk_timerproc();
  38
  39                 j = tick_1s - 1;
  40                 if (j == 0) {
  41                         system_tick();
  42                         j = 100;
  43                 }
  44                 tick_1s = j;
  45                 i = 0;
  46         }
  47         tick_10ms = i;
  48 }
  49
  50
  51 /*--------------------------------------------------------------------------*/
  52
  53 uint32_t get_timer(uint32_t base)
  54 {
  55         uint32_t ret;
  56         ATOMIC_BLOCK(ATOMIC_FORCEON)
  57         {
  58                 ret = timestamp;
  59         }
  60         return ret - base;
  61 }