rtc.c
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/*
* Copyright (C) 2016 OTA keys S.A.
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu_stm32f2
* @{
* @file
* @brief Low-level RTC driver implementation
* @author Vincent Dupont <vincent@otakeys.com>
* @}
*/
#include <time.h>
#include "cpu.h"
#include "periph/rtc.h"
#include "periph_conf.h"
/* guard file in case no RTC device was specified */
#if RTC_NUMOF
#define RTC_WRITE_PROTECTION_KEY1 (0xCA)
#define RTC_WRITE_PROTECTION_KEY2 (0x53)
#define RTC_SYNC_PRESCALER (0xff) /**< prescaler for 32.768 kHz oscillator */
#define RTC_ASYNC_PRESCALER (0x7f) /**< prescaler for 32.768 kHz oscillator */
#define MCU_YEAR_OFFSET (100) /**< struct tm counts years since 1900
but RTC has only two-digit year
hence the offset of 100 years. */
typedef struct {
rtc_alarm_cb_t cb; /**< callback called from RTC interrupt */
void *arg; /**< argument passed to the callback */
} rtc_state_t;
static rtc_state_t rtc_callback;
static uint8_t byte2bcd(uint8_t value);
/**
* @brief Initializes the RTC to use LSE (external 32.768 kHz oscillator) as a
* clocl source. Verify that your board has this oscillator. If other clock
* source is used, then also the prescaler constants should be changed.
*/
void rtc_init(void)
{
/* Enable write access to RTC registers */
periph_clk_en(APB1, RCC_APB1ENR_PWREN);
PWR->CR |= PWR_CR_DBP;
/* Reset RTC domain */
RCC->BDCR |= RCC_BDCR_BDRST;
RCC->BDCR &= ~(RCC_BDCR_BDRST);
/* Enable the LSE clock (external 32.768 kHz oscillator) */
RCC->BDCR &= ~(RCC_BDCR_LSEON);
RCC->BDCR &= ~(RCC_BDCR_LSEBYP);
RCC->BDCR |= RCC_BDCR_LSEON;
while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0) {
}
/* Switch RTC to LSE clock source */
RCC->BDCR &= ~(RCC_BDCR_RTCSEL);
RCC->BDCR |= RCC_BDCR_RTCSEL_0;
/* Enable the RTC */
RCC->BDCR |= RCC_BDCR_RTCEN;
/* Unlock RTC write protection */
RTC->WPR = RTC_WRITE_PROTECTION_KEY1;
RTC->WPR = RTC_WRITE_PROTECTION_KEY2;
/* Enter RTC Init mode */
RTC->ISR = 0;
RTC->ISR |= RTC_ISR_INIT;
while ((RTC->ISR & RTC_ISR_INITF) == 0) {
}
/* Set 24-h clock */
RTC->CR &= ~RTC_CR_FMT;
/* Timestamps enabled */
RTC->CR |= RTC_CR_TSE;
/* Configure the RTC PRER */
RTC->PRER = RTC_SYNC_PRESCALER;
RTC->PRER |= (RTC_ASYNC_PRESCALER << 16);
/* Exit RTC init mode */
RTC->ISR &= (uint32_t) ~RTC_ISR_INIT;
/* Enable RTC write protection */
RTC->WPR = 0xff;
}
int rtc_set_time(struct tm *time)
{
/* Enable write access to RTC registers */
periph_clk_en(APB1, RCC_APB1ENR_PWREN);
PWR->CR |= PWR_CR_DBP;
/* Unlock RTC write protection */
RTC->WPR = RTC_WRITE_PROTECTION_KEY1;
RTC->WPR = RTC_WRITE_PROTECTION_KEY2;
/* Enter RTC Init mode */
RTC->ISR |= RTC_ISR_INIT;
while ((RTC->ISR & RTC_ISR_INITF) == 0) {
}
/* Set 24-h clock */
RTC->CR &= ~RTC_CR_FMT;
RTC->DR = ((((uint32_t)byte2bcd(time->tm_year - MCU_YEAR_OFFSET) << 16) & (RTC_DR_YT | RTC_DR_YU)) |
(((uint32_t)byte2bcd(time->tm_mon + 1) << 8) & (RTC_DR_MT | RTC_DR_MU)) |
(((uint32_t)byte2bcd(time->tm_mday) << 0) & (RTC_DR_DT | RTC_DR_DU)));
RTC->TR = ((((uint32_t)byte2bcd(time->tm_hour) << 16) & (RTC_TR_HT | RTC_TR_HU)) |
(((uint32_t)byte2bcd(time->tm_min) << 8) & (RTC_TR_MNT | RTC_TR_MNU)) |
(((uint32_t)byte2bcd(time->tm_sec) << 0) & (RTC_TR_ST | RTC_TR_SU)));
/* Exit RTC init mode */
RTC->ISR &= (uint32_t) ~RTC_ISR_INIT;
/* Enable RTC write protection */
RTC->WPR = 0xFF;
return 0;
}
int rtc_get_time(struct tm *time)
{
time->tm_year = MCU_YEAR_OFFSET;
time->tm_year += (((RTC->DR & RTC_DR_YT) >> 20) * 10) + ((RTC->DR & RTC_DR_YU) >> 16);
time->tm_mon = (((RTC->DR & RTC_DR_MT) >> 12) * 10) + ((RTC->DR & RTC_DR_MU) >> 8) - 1;
time->tm_mday = (((RTC->DR & RTC_DR_DT) >> 4) * 10) + ((RTC->DR & RTC_DR_DU) >> 0);
time->tm_hour = (((RTC->TR & RTC_TR_HT) >> 20) * 10) + ((RTC->TR & RTC_TR_HU) >> 16);
if (RTC->TR & RTC_TR_PM) {
/* 12PM is noon */
if (time->tm_hour != 12) {
time->tm_hour += 12;
}
}
else if ((RTC->CR & RTC_CR_FMT) && time->tm_hour == 12) {
/* 12AM is midnight */
time->tm_hour -= 12;
}
time->tm_min = (((RTC->TR & RTC_TR_MNT) >> 12) * 10) + ((RTC->TR & RTC_TR_MNU) >> 8);
time->tm_sec = (((RTC->TR & RTC_TR_ST) >> 4) * 10) + ((RTC->TR & RTC_TR_SU) >> 0);
return 0;
}
int rtc_set_alarm(struct tm *time, rtc_alarm_cb_t cb, void *arg)
{
/* Enable write access to RTC registers */
periph_clk_en(APB1, RCC_APB1ENR_PWREN);
PWR->CR |= PWR_CR_DBP;
/* Unlock RTC write protection */
RTC->WPR = RTC_WRITE_PROTECTION_KEY1;
RTC->WPR = RTC_WRITE_PROTECTION_KEY2;
/* Enter RTC Init mode */
RTC->ISR |= RTC_ISR_INIT;
while ((RTC->ISR & RTC_ISR_INITF) == 0) {
}
RTC->CR &= ~(RTC_CR_ALRAE);
while ((RTC->ISR & RTC_ISR_ALRAWF) == 0) {
}
RTC->ALRMAR &= ~(RTC_ALRMAR_MSK1 | RTC_ALRMAR_MSK2 | RTC_ALRMAR_MSK3 | RTC_ALRMAR_MSK4);
RTC->ALRMAR = ((((uint32_t)byte2bcd(time->tm_mday) << 24) & (RTC_ALRMAR_DT | RTC_ALRMAR_DU)) |
(((uint32_t)byte2bcd(time->tm_hour) << 16) & (RTC_ALRMAR_HT | RTC_ALRMAR_HU)) |
(((uint32_t)byte2bcd(time->tm_min) << 8) & (RTC_ALRMAR_MNT | RTC_ALRMAR_MNU)) |
(((uint32_t)byte2bcd(time->tm_sec) << 0) & (RTC_ALRMAR_ST | RTC_ALRMAR_SU)));
/* Enable Alarm A */
RTC->CR |= RTC_CR_ALRAE;
RTC->CR |= RTC_CR_ALRAIE;
RTC->ISR &= ~(RTC_ISR_ALRAF);
/* Exit RTC init mode */
RTC->ISR &= (uint32_t) ~RTC_ISR_INIT;
/* Enable RTC write protection */
RTC->WPR = 0xFF;
EXTI->IMR |= EXTI_IMR_MR17;
EXTI->RTSR |= EXTI_RTSR_TR17;
NVIC_SetPriority(RTC_Alarm_IRQn, 10);
NVIC_EnableIRQ(RTC_Alarm_IRQn);
rtc_callback.cb = cb;
rtc_callback.arg = arg;
return 0;
}
int rtc_get_alarm(struct tm *time)
{
time->tm_year = MCU_YEAR_OFFSET;
time->tm_year += (((RTC->DR & RTC_DR_YT) >> 20) * 10) + ((RTC->DR & RTC_DR_YU) >> 16);
time->tm_mon = (((RTC->DR & RTC_DR_MT) >> 12) * 10) + ((RTC->DR & RTC_DR_MU) >> 8) - 1;
time->tm_mday = (((RTC->ALRMAR & RTC_ALRMAR_DT) >> 28) * 10) + ((RTC->ALRMAR & RTC_ALRMAR_DU) >> 24);
time->tm_hour = (((RTC->ALRMAR & RTC_ALRMAR_HT) >> 20) * 10) + ((RTC->ALRMAR & RTC_ALRMAR_HU) >> 16);
if ((RTC->ALRMAR & RTC_ALRMAR_PM) && (RTC->CR & RTC_CR_FMT)) {
time->tm_hour += 12;
}
time->tm_min = (((RTC->ALRMAR & RTC_ALRMAR_MNT) >> 12) * 10) + ((RTC->ALRMAR & RTC_ALRMAR_MNU) >> 8);
time->tm_sec = (((RTC->ALRMAR & RTC_ALRMAR_ST) >> 4) * 10) + ((RTC->ALRMAR & RTC_ALRMAR_SU) >> 0);
return 0;
}
void rtc_clear_alarm(void)
{
/* Disable Alarm A */
RTC->CR &= RTC_CR_ALRAE;
RTC->CR &= RTC_CR_ALRAIE;
rtc_callback.cb = NULL;
rtc_callback.arg = NULL;
}
void rtc_poweron(void)
{
/* RTC on STM32F2 is online even on sleep modes. No need to power on. */
}
void rtc_poweroff(void)
{
/* Enable write access to RTC registers */
periph_clk_en(APB1, RCC_APB1ENR_PWREN);
PWR->CR |= PWR_CR_DBP;
/* Reset RTC domain */
RCC->BDCR |= RCC_BDCR_BDRST;
RCC->BDCR &= ~(RCC_BDCR_BDRST);
/* Disable the RTC */
RCC->BDCR &= ~RCC_BDCR_RTCEN;
/* Disable LSE clock */
RCC->BDCR &= ~(RCC_BDCR_LSEON);
}
void isr_rtc_alarm(void)
{
if (RTC->ISR & RTC_ISR_ALRAF) {
if (rtc_callback.cb != NULL) {
rtc_callback.cb(rtc_callback.arg);
}
RTC->ISR &= ~RTC_ISR_ALRAF;
}
EXTI->PR |= EXTI_PR_PR17;
cortexm_isr_end();
}
/**
* Convert a number from unsigned to BCD
*
* @param[in] value to be converted
* @return BCD representation of the value
*/
static uint8_t byte2bcd(uint8_t value)
{
uint8_t bcdhigh = 0;
while (value >= 10) {
bcdhigh++;
value -= 10;
}
return ((uint8_t)(bcdhigh << 4) | value);
}
#endif /* RTC_NUMOF */