sys_time_arch.c

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/*
 * Copyright (C) 2009-2011 The Paparazzi Team
 *
 * This file is part of paparazzi.
 *
 * paparazzi is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * paparazzi is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with paparazzi; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
 
#include "mcu_periph/sys_time.h"
#include "mcu_periph/sys_time_arch.h"
 
#include "libopencm3/cm3/systick.h"
 
#ifdef SYS_TIME_LED
#include "led.h"
#endif
 
#ifndef USE_OCM3_SYSTICK_INIT
#define USE_OCM3_SYSTICK_INIT 1
#endif
 
void sys_tick_handler(void);
 
void sys_time_arch_init(void)
{
  /* run cortex systick timer with 72MHz (FIXME only 72 or does it work with 168MHz???) */
#if USE_OCM3_SYSTICK_INIT
  systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
#endif
  sys_time.cpu_ticks_per_sec = AHB_CLK;
 
  /* cpu ticks per desired sys_time timer step */
  sys_time.resolution_cpu_ticks = (uint32_t)(sys_time.resolution * sys_time.cpu_ticks_per_sec + 0.5);
 
#if USE_OCM3_SYSTICK_INIT
  /* The timer interrupt is activated on the transition from 1 to 0,
   * therefore it activates every n+1 clock ticks.
   */
  systick_set_reload(sys_time.resolution_cpu_ticks - 1);
 
  systick_interrupt_enable();
  systick_counter_enable();
#endif
}
 
 
// FIXME : nb_tick rollover ???
//
// 97 days at 512hz
// 12 hours at 100khz
//
void sys_tick_handler(void)
{
  sys_time.nb_tick++;
 
  sys_time.nb_sec_rem += sys_time.resolution_cpu_ticks;
  if (sys_time.nb_sec_rem >= sys_time.cpu_ticks_per_sec) {
    sys_time.nb_sec_rem -= sys_time.cpu_ticks_per_sec;
    sys_time.nb_sec++;
 
#ifdef SYS_TIME_LED
    LED_TOGGLE(SYS_TIME_LED);
#endif
  }
  for (unsigned int i = 0; i < SYS_TIME_NB_TIMER; i++) {
    if (sys_time.timer[i].in_use &&
        sys_time.nb_tick >= sys_time.timer[i].end_time) {
      sys_time.timer[i].end_time += sys_time.timer[i].duration;
      sys_time.timer[i].elapsed = true;
      if (sys_time.timer[i].cb) {
        sys_time.timer[i].cb(i);
      }
    }
  }
}
 
void sys_time_usleep(uint32_t us)
{
  // start time
  uint32_t start = systick_get_value();
  // max time of one full counter cycle (n + 1 ticks)
  uint32_t DT = usec_of_cpu_ticks(systick_get_reload() + 1);
  // number of cycles
  uint32_t n = us / DT;
  // remaining number of cpu ticks
  uint32_t rem = cpu_ticks_of_usec(us % DT);
  // end time depend on the current value of the counter
  uint32_t end;
  if (rem < start) {
    end = start - rem;
  } else {
    // one more count flag is required
    n++;
    end = systick_get_reload() - rem + start;
  }
  // count number of cycles (when counter reachs 0)
  while (n) {
    while (!systick_get_countflag());
    n--;
  }
  // wait remaining ticks
  while (systick_get_value() > end);
}
 
void sys_time_msleep(uint32_t ms) {
  sys_time_usleep(ms*1000);
}