File content as of revision 76:aeb1df146756:

/* mbed Microcontroller Library
 * Copyright (c) 2014, 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 "us_ticker_api.h"
#include "PeripheralNames.h"

// Timers selection:
// The Master timer clocks the Slave timer

#define TIM_MST     TIM3
#define TIM_MST_IRQ TIM3_IRQn
#define TIM_MST_RCC RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE)

#define TIM_SLV     TIM15
#define TIM_SLV_IRQ TIM15_IRQn
#define TIM_SLV_RCC RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM15, ENABLE)

#define MST_SLV_ITR TIM_TS_ITR1

int us_ticker_inited = 0;

void us_ticker_init(void) {
    
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;

    if (us_ticker_inited) return;
    us_ticker_inited = 1;
  
    // Enable Timers clock
    TIM_MST_RCC;
    TIM_SLV_RCC;
  
    // Master and Slave timers time base configuration
    TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
    TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
    TIM_TimeBaseStructure.TIM_Prescaler = (uint16_t)(SystemCoreClock / 1000000) - 1; // 1 µs tick
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM_MST, &TIM_TimeBaseStructure);
    TIM_TimeBaseStructure.TIM_Prescaler = 0;
    TIM_TimeBaseInit(TIM_SLV, &TIM_TimeBaseStructure);  

    // Master timer configuration
    TIM_OCStructInit(&TIM_OCInitStructure);
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM_MST, &TIM_OCInitStructure);
    TIM_SelectMasterSlaveMode(TIM_MST, TIM_MasterSlaveMode_Enable);
    TIM_SelectOutputTrigger(TIM_MST, TIM_TRGOSource_Update);
    
    // Slave timer configuration
    TIM_SelectSlaveMode(TIM_SLV, TIM_SlaveMode_External1);
    // The connection between Master and Slave is done here
    TIM_SelectInputTrigger(TIM_SLV, MST_SLV_ITR);
  
    // Enable timers
    TIM_Cmd(TIM_SLV, ENABLE);
    TIM_Cmd(TIM_MST, ENABLE);
}

uint32_t us_ticker_read() {
    uint32_t counter, counter2;
    if (!us_ticker_inited) us_ticker_init();
    // A situation might appear when Master overflows right after Slave is read and before the
    // new (overflowed) value of Master is read. Which would make the code below consider the
    // previous (incorrect) value of Slave and the new value of Master, which would return a
    // value in the past. Avoid this by computing consecutive values of the timer until they
    // are properly ordered.
    counter = (uint32_t)((uint32_t)TIM_GetCounter(TIM_SLV) << 16);
    counter += (uint32_t)TIM_GetCounter(TIM_MST);
    while (1) {
        counter2 = (uint32_t)((uint32_t)TIM_GetCounter(TIM_SLV) << 16);
        counter2 += (uint32_t)TIM_GetCounter(TIM_MST);
        if (counter2 > counter) {
            break;
        }
        counter = counter2;
    }
    return counter2;
}

void us_ticker_set_interrupt(unsigned int timestamp) {
    if (timestamp > 0xFFFF) {
        TIM_SetCompare1(TIM_SLV, (uint16_t)((timestamp >> 16) & 0xFFFF));
        TIM_ITConfig(TIM_SLV, TIM_IT_CC1, ENABLE);
        NVIC_SetVector(TIM_SLV_IRQ, (uint32_t)us_ticker_irq_handler);
        NVIC_EnableIRQ(TIM_SLV_IRQ);      
    }
    else {
        TIM_SetCompare1(TIM_MST, (uint16_t)timestamp);
        TIM_ITConfig(TIM_MST, TIM_IT_CC1, ENABLE);  
        NVIC_SetVector(TIM_MST_IRQ, (uint32_t)us_ticker_irq_handler);
        NVIC_EnableIRQ(TIM_MST_IRQ);
    }
}

void us_ticker_disable_interrupt(void) {
    TIM_ITConfig(TIM_MST, TIM_IT_CC1, DISABLE);
    TIM_ITConfig(TIM_SLV, TIM_IT_CC1, DISABLE);
}

void us_ticker_clear_interrupt(void) {
    TIM_ClearITPendingBit(TIM_MST, TIM_IT_CC1);
    TIM_ClearITPendingBit(TIM_SLV, TIM_IT_CC1);
}