pios_rtc.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, see <http://www.gnu.org/licenses/>
 */

/* Project Includes */
#include "pios.h"

#if defined(PIOS_INCLUDE_RTC)
#include <pios_rtc_priv.h>

#ifndef PIOS_RTC_PRESCALER
#define PIOS_RTC_PRESCALER 100
#endif

struct rtc_callback_entry {
  void (*fn)(uintptr_t);
  uintptr_t data;
};

#define PIOS_RTC_MAX_CALLBACKS 3
struct rtc_callback_entry rtc_callback_list[PIOS_RTC_MAX_CALLBACKS];
static uint8_t rtc_callback_next = 0;

void PIOS_RTC_Init(const struct pios_rtc_cfg * cfg)
{
        RCC_BackupResetCmd(ENABLE);
        RCC_BackupResetCmd(DISABLE);
        RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);
        PWR_BackupAccessCmd(ENABLE);
        // Divide external 8 MHz clock by 32 to 250kHz
        RCC_RTCCLKConfig(cfg->clksrc);
        RCC_RTCCLKCmd(ENABLE);

        RTC_WakeUpCmd(DISABLE);
        // Divide 250kHz Mhz clock by 16 to 15625Hz
        RTC_WakeUpClockConfig(RTC_WakeUpClock_RTCCLK_Div16);
        // Divide 15625Hz by 25 to get 625 Hz
        RTC_SetWakeUpCounter(cfg->prescaler); //cfg->prescaler);
        RTC_WakeUpCmd(ENABLE);
        
        /* Configure and enable the RTC Second interrupt */
        EXTI_InitTypeDef ExtiInit = {
                .EXTI_Line = EXTI_Line20, // matches above GPIO pin
                .EXTI_Mode = EXTI_Mode_Interrupt,
                .EXTI_Trigger = EXTI_Trigger_Rising,
                .EXTI_LineCmd = ENABLE,
        };
        EXTI_Init((EXTI_InitTypeDef*)&ExtiInit);
        NVIC_Init((NVIC_InitTypeDef*)&cfg->irq.init);
        RTC_ITConfig(RTC_IT_WUT, ENABLE);
        
        RTC_ClearFlag(RTC_FLAG_WUTF);
}

uint32_t PIOS_RTC_Counter()
{
        return RTC_GetWakeUpCounter();
}

/* FIXME: This shouldn't use hard-coded clock rates, dividers or prescalers.
 *        Should get these from the cfg struct passed to init.
 */
float PIOS_RTC_Rate()
{
        return (float) (8e6 / 128) / (1 + PIOS_RTC_PRESCALER);
}

float PIOS_RTC_MsPerTick() 
{
        return 1000.0f / PIOS_RTC_Rate();
}

/* TODO: This needs a mutex around rtc_callbacks[] */
bool PIOS_RTC_RegisterTickCallback(void (*fn)(uintptr_t id), uintptr_t data)
{
        struct rtc_callback_entry * cb;
        if (rtc_callback_next >= PIOS_RTC_MAX_CALLBACKS) {
                return false;
        }

        cb = &rtc_callback_list[rtc_callback_next++];

        cb->fn   = fn;
        cb->data = data;
        return true;
}

void PIOS_RTC_irq_handler (void)
{
        PIOS_IRQ_Prologue();

        if (RTC_GetITStatus(RTC_IT_WUT))
        {
                /* Call all registered callbacks */
                for (uint8_t i = 0; i < rtc_callback_next; i++) {
                        struct rtc_callback_entry * cb = &rtc_callback_list[i];
                        if (cb->fn) {
                                (cb->fn)(cb->data);
                        }
                }

                /* Clear the RTC Second interrupt */
                RTC_ClearITPendingBit(RTC_IT_WUT);
        }

        if (EXTI_GetITStatus(EXTI_Line20) != RESET)
                EXTI_ClearITPendingBit(EXTI_Line20);

        PIOS_IRQ_Epilogue();
}
#endif