File content as of revision 440:8a0b45cd594f:

/* 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 "rtc_api.h"

#if DEVICE_RTC

#include "wait_api.h"

#define LSE_STARTUP_TIMEOUT ((uint16_t)700) // delay in ms

static int rtc_inited = 0;

void rtc_init(void)
{
    uint32_t StartUpCounter = 0;
    uint32_t LSEStatus = 0;
    uint32_t rtc_freq = 0;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE); // Enable PWR and Backup clock

    PWR_BackupAccessCmd(ENABLE); // Allow access to Backup Domain

    BKP_DeInit(); // Reset Backup Domain

    // Enable LSE clock
    RCC_LSEConfig(RCC_LSE_ON);

    // Wait till LSE is ready
    do {
        LSEStatus = RCC_GetFlagStatus(RCC_FLAG_LSERDY);
        wait_ms(1);
        StartUpCounter++;
    } while ((LSEStatus == 0) && (StartUpCounter <= LSE_STARTUP_TIMEOUT));

    if (StartUpCounter > LSE_STARTUP_TIMEOUT) {
        // The LSE has not started, use LSI instead.
        // The RTC Clock may vary due to LSI frequency dispersion.
        RCC_LSEConfig(RCC_LSE_OFF);
        RCC_LSICmd(ENABLE); // Enable LSI
        while (RCC_GetFlagStatus(RCC_FLAG_LSIRDY) == RESET) {} // Wait until ready
        RCC_RTCCLKConfig(RCC_RTCCLKSource_LSI); // Select the RTC Clock Source
        rtc_freq = 40000; // [TODO] To be measured precisely using a timer input capture
    } else {
        // The LSE has correctly started
        RCC_RTCCLKConfig(RCC_RTCCLKSource_LSE); // Select the RTC Clock Source
        rtc_freq = LSE_VALUE;
    }

    RCC_RTCCLKCmd(ENABLE); // Enable RTC Clock

    RTC_WaitForSynchro(); // Wait for RTC registers synchronization

    RTC_WaitForLastTask(); // Wait until last write operation on RTC registers has finished

    // Set RTC period to 1 sec
    RTC_SetPrescaler(rtc_freq - 1);

    RTC_WaitForLastTask(); // Wait until last write operation on RTC registers has finished

    rtc_inited = 1;
}

void rtc_free(void)
{
    // Disable RTC, LSE and LSI clocks
    PWR_BackupAccessCmd(ENABLE); // Allow access to Backup Domain
    RCC_RTCCLKCmd(DISABLE);
    RCC_LSEConfig(RCC_LSE_OFF);
    RCC_LSICmd(DISABLE);

    rtc_inited = 0;
}

int rtc_isenabled(void)
{
    return rtc_inited;
}

time_t rtc_read(void)
{
    return (time_t)RTC_GetCounter();
}

void rtc_write(time_t t)
{
    RTC_WaitForLastTask(); // Wait until last write operation on RTC registers has finished
    RTC_SetCounter(t); // Change the current time
    RTC_WaitForLastTask(); // Wait until last write operation on RTC registers has finished
}

#endif