File content as of revision 136:5728e9819171:

/* mbed Microcontroller Library
 * Copyright (c) 2015, STMicroelectronics
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. Neither the name of STMicroelectronics nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <stddef.h>
#include <stdbool.h>
#include "us_ticker_api.h"
#include "PeripheralNames.h"

// Timer selection
#define TIM_MST TIM21

static TIM_HandleTypeDef TimMasterHandle;
static int us_ticker_inited = 0;
static bool us_ticker_stabilized = false;

volatile uint16_t SlaveCounter = 0;
volatile uint32_t oc_int_part = 0;
volatile uint16_t oc_rem_part = 0;

void set_compare(uint16_t count)
{
    TimMasterHandle.Instance = TIM_MST;
    // Set new output compare value
    __HAL_TIM_SetCompare(&TimMasterHandle, TIM_CHANNEL_1, count);
    // Enable IT
    __HAL_TIM_ENABLE_IT(&TimMasterHandle, TIM_IT_CC1);
}

void us_ticker_init(void)
{
    if (us_ticker_inited) return;
    us_ticker_inited = 1;

    HAL_InitTick(0); // The passed value is not used
}

uint32_t us_ticker_read()
{
    volatile uint16_t cntH_old, cntH, cntL;

    if (!us_ticker_inited) us_ticker_init();

    // There's a situation where the first tick still may overflow and to avoid
    // it we need to check if our ticker has stabilized and due to that we need
    // to return only the lower part of your 32 bit software timer.
    if (us_ticker_stabilized) {
        do {
            // For some reason on L0xx series we need to read and clear the 
            // overflow flag which give extra time to propelry handle possible
            // hiccup after ~60s
            if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_CC1OF) == SET) {
                __HAL_TIM_CLEAR_FLAG(&TimMasterHandle, TIM_FLAG_CC1OF);
            }
            cntH_old = SlaveCounter;
            if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_UPDATE) == SET) {
             cntH_old += 1;
            }
            cntL = TIM_MST->CNT;
 
            cntH = SlaveCounter;
            if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_UPDATE) == SET) {
                cntH += 1;
            }
        } while(cntH_old != cntH);
    } else {
        us_ticker_stabilized = true;
        return (uint32_t) TIM_MST->CNT;
    } 
    
    // Glue the upper and lower part together to get a 32 bit timer
    return (uint32_t)(cntH << 16 | cntL);
}

void us_ticker_set_interrupt(timestamp_t timestamp)
{
    int delta = (int)((uint32_t)timestamp - us_ticker_read());
    uint16_t cval = TIM_MST->CNT;

    if (delta <= 0) { // This event was in the past
        us_ticker_irq_handler();
    } else {
        oc_int_part = (uint32_t)(delta >> 16);
        oc_rem_part = (uint16_t)(delta & 0xFFFF);
        if (oc_rem_part <= (0xFFFF - cval)) {
            set_compare(cval + oc_rem_part);
            oc_rem_part = 0;
        } else {
            set_compare(0xFFFF);
            oc_rem_part = oc_rem_part - (0xFFFF - cval);
        }
    }
}

void us_ticker_disable_interrupt(void)
{
    TimMasterHandle.Instance = TIM_MST;
    __HAL_TIM_DISABLE_IT(&TimMasterHandle, TIM_IT_CC1);
}

void us_ticker_clear_interrupt(void)
{
    TimMasterHandle.Instance = TIM_MST;
    if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_CC1) == SET) {
        __HAL_TIM_CLEAR_FLAG(&TimMasterHandle, TIM_FLAG_CC1);
    }
}