millisec_timer.h

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/** @file
 * \brief Portable millisecond timer
 *
 * On microcontrollers, \ref MILLISEC_TIMER_NOW will be declared
 * and can be setup to increment every millisecond.
 *
 * For Cortex-M, put:
 *
 * 1) #include <libopencm3/cm3/nvic.h> at the top of your main file
 *
 * 2) \ref MILLISEC_TIMER_SYSTICK_IT; outside of any function to
 *    define the systick interrupt
 *
 * 3) \ref millisec_timer_systick_setup(); with rcc_ahb_frequency as
 *    its argument,in the setup portion of your main function. It's
 *    probably best to put before other things.
 *
 * For AVR, put:
 *
 * 1) #include <avr/interrupt.h>
 *    #include <avr/io.h>
 *    #include <util/atomic.h>
 *    at the top of your main file
 *
 * 2) \ref MILLISEC_TIMER_AVR_TIMER0_ISR; outside of any function to
 *    define Timer0 ISR.
 *
 * 3) \ref millisec_timer_avr_timer0_setup_16MHz(); in the setup portion
 *    of your main function to setup the timer for 16 MHz clock speed.
 *
 */
 
#ifndef MILLISEC_TIMER_H
#define MILLISEC_TIMER_H
 
#include <inttypes.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#ifdef linux
#include <stdio.h>
#endif
#ifdef __ARM_ARCH
#include <libopencm3/cm3/systick.h>
#endif
 
typedef uint32_t millisec_timer_unit_t;
 
/** \brief portable millisecond timer
 *
 *  It's designed to be easy to use and handle wraparound properly (which
 * happens every 49.7 days for uint32_t).
 *
 */
typedef struct __millisec_timer {
  bool enabled;
  millisec_timer_unit_t set_time;
  millisec_timer_unit_t expire_time;
} millisec_timer;
 
/** \brief Set timer to expire in the future
 *
 * Sets and enables timer to expire rel ms in the future.
 *
 * This sets the set_time to now and the expire_time to set_time + rel
 *
 */
void millisec_timer_set_rel(millisec_timer *timer,
                            const millisec_timer_unit_t now,
                            const millisec_timer_unit_t rel);
 
/** \brief Check if timer has expired & if so, disable it
 *
 * If timer is enabled and it's expired, return true and disable the timer.
 * If not enabled or the time hasn't expired, return false.
 *
 */
bool millisec_timer_is_expired(millisec_timer *timer,
                               const millisec_timer_unit_t now);
 
/** \brief Check if timer has expired & if so, re-enable for the same interval
 *
 * If timer is enabled and it's set time has expired:
 *  1) set the new expiration time to be the old expire time + (old expire time
 * - old set time) 2) set the new set time to be the old expire time 3) return
 * true. If not enabled or the time hasn't expired, return false.
 *
 */
bool millisec_timer_is_expired_repeat(millisec_timer *timer,
                                      const millisec_timer_unit_t now);
 
#if defined(__ARM_ARCH) || defined(__AVR)
#pragma GCC diagnostic ignored "-Wunused-variable"
#pragma GCC diagnostic push
/** \brief A counter that increments every millisecond
 *
 * This value will increment every millisecond, if everything is setup
 * correctly.
 *
 */
static uint32_t MILLISEC_TIMER_NOW = 0;
#pragma GCC diagnostic pop
#endif
 
#ifdef __ARM_ARCH
/** \brief Millisecond timer SysTick interrupt
 *
 *  Implements an interrupt handler that increments MILLISEC_TIMER_NOW
 *
 */
#define MILLISEC_TIMER_SYSTICK_IT                                              \
  void sys_tick_handler(void) { MILLISEC_TIMER_NOW++; }
 
/** \brief Setup the systick timer
 *
 * Configures the systick timer to raise the interrupt every millisecond.
 *
 */
void millisec_timer_systick_setup(uint32_t ahb_frequency);
#endif
 
#ifdef __AVR
/** \brief Millisecond timer SysTick interrupt
 *
 *  Implements an interrupt handler that increments MILLISEC_TIMER_NOW
 *
 */
#define MILLISEC_TIMER_AVR_TIMER0_ISR                                          \
  ISR(TIMER0_COMPA_vect) { MILLISEC_TIMER_NOW++; }
 
/** \brief Setup the systick timer
 *
 * Configures Timer0 to raise the TIMER0_COMPA interrupt every millisecond.
 *
 * It's a good idea to use ATOMIC blocks around MILLISEC_TIMER_NOW access.
 *
 */
#define millisec_timer_avr_timer0_setup_16MHz()                                \
  TCCR0B |= 0x3;                                                               \
  TCCR0A |= 2;                                                                 \
  OCR0A = 250;                                                                 \
  TIMSK0 |= 1 << OCIE0A
 
#endif
 
#endif