timely-reference/SystemTime.cpp

/*
 * Copyright (C) 2019  Max Regan
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "SystemTime.h"
#include "macros.h"

namespace BSP {

using Common::ReturnCode;
using Common::time_t;

uint32_t SystemTimer::m_seconds(0);
RTC_TypeDef *SystemTimer::m_rtc = nullptr;

void SystemTimer::enable_rtc_write()
{
    /*<! Disable write protection */
    RTC->WPR = 0xCA;
    RTC->WPR = 0x53;
}

void SystemTimer::disable_rtc_write()
{
    /*<! Disable write protection */
    RTC->WPR = 0x00;
}

void SystemTimer::enable_rtc_wakeup_interrupt()
{
    CLR(RTC->CR, RTC_CR_WUTE);
    while (!(RTC->ISR & RTC_ISR_WUTWF)) {}
    SET_TO(RTC->WUTR, RTC_WUTR_WUT, 0);
    SET_TO(RTC->CR, RTC_CR_WUCKSEL, RTC_CR_WUCKSEL_2);

    SET(EXTI->IMR, EXTI_IMR_IM20);
    SET(EXTI->EMR, EXTI_EMR_EM20);
    SET(EXTI->RTSR, EXTI_RTSR_RT20);

    NVIC_EnableIRQ(RTC_IRQn);
    NVIC_SetPriority(RTC_IRQn, 0);

    SET(RTC->CR, RTC_CR_WUTE | RTC_CR_WUTIE);
}

ReturnCode SystemTimer::init_hw()
{
    uint32_t temp = RCC->CSR;

    SET(RCC->CSR, RCC_CSR_RTCRST);
    SET(RCC->APB1ENR, RCC_APB1ENR_PWREN);
    SET(PWR->CR, PWR_CR_DBP);

    /*<! Set RTC input clock to the LSI (low-speed internal 32.768kHz) clock */
    SET(temp, RCC_CSR_LSEON);
    SET_TO(temp, RCC_CSR_RTCSEL, RCC_CSR_RTCSEL_0);
    SET(temp, RCC_CSR_RTCEN);
    RCC->CSR = temp;

    while (!(RCC->CSR & RCC_CSR_LSERDY)) {}

    enable_rtc_write();

    RTC->ISR = RTC_ISR_INIT;
    while (!(RTC->ISR & RTC_ISR_INITF)) {}

    // FIXME: Make this use the minimum prescaler value
    /*<! Set the Clock Prescalers (32.768kHz / 128 / 256 = 1Hz */
    /*<! Set the Async prescaler to the Maximum (divide the clock by 128) */
    SET_TO(RTC->PRER, RTC_PRER_PREDIV_A, 0);
    /*<! Set the Syncronous scaler (divide the clock by 255 + 1) */
    SET_TO(RTC->PRER, RTC_PRER_PREDIV_S, (LSE_CLOCK_FREQ - 1));

    /*<! Load initial date and time */
    // TODO
    /* uint32_t time = 0; */
    /* uint32_t date = 0; */
    /*<! Set the date and time format */
    // TODO: currently defaults to 24hr

    // 12-Hour format
    SET(RTC->CR, RTC_CR_FMT);

    uint32_t time = 0;
    SET(time, RTC_TR_PM);
    SET_TO(time, RTC_TR_HT, 1 << RTC_TR_HT_Pos);
    SET_TO(time, RTC_TR_HU, 2 << RTC_TR_HU_Pos);
    SET_TO(time, RTC_TR_MNT, 5 << RTC_TR_MNT_Pos);
    SET_TO(time, RTC_TR_MNU, 9 << RTC_TR_MNU_Pos);
    SET_TO(time, RTC_TR_ST, 0 << RTC_TR_ST_Pos);
    SET_TO(time, RTC_TR_SU, 0 << RTC_TR_SU_Pos);
    RTC->TR = time;


    CLR(RTC->ISR, RTC_ISR_INIT);

    enable_rtc_wakeup_interrupt();

    disable_rtc_write();

    return ReturnCode::OK;
}

ReturnCode SystemTimer::init(RTC_TypeDef *rtc)
{
    if (rtc == nullptr) {
        return ReturnCode::FAIL;
    }

    m_rtc = rtc;
    m_seconds = 0;

    init_hw();

    return ReturnCode::OK;
}

ReturnCode SystemTimer::get_time(time_t &time)
{
    if (m_rtc == nullptr) {
        return ReturnCode::FAIL;
    }

    uint32_t new_secs, old_secs, ssr, subsecond;
    do {
        old_secs = m_seconds;
        ssr = m_rtc->SSR & 0xFFFF;
        new_secs = m_seconds;
    } while (new_secs != old_secs);

    new_secs = new_secs * LSE_CLOCK_FREQ;
    /** SSR is a countdown register */
    subsecond = (new_secs + LSE_CLOCK_FREQ - 1 - ssr) * Common::Time::MILLIS_PER_SEC / LSE_CLOCK_FREQ;
    time += Common::Time::millis(subsecond);

    return ReturnCode::OK;
}

void SystemTimer::increment_seconds()
{
    m_seconds++;
}

extern "C" void RTC_IRQHandler(void);

void RTC_IRQHandler() {
    SystemTimer::increment_seconds();
    // Clear the interrupt in the EXTI
    SET(EXTI->PR, EXTI_PR_PIF20);
    // Clear the interrupt in the RTC
    CLR(RTC->ISR, RTC_ISR_WUTF);
}

}