stm32f1/lib/rtc_ds1307.c

/* 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/>.
 *
 */
/** library to communicate with the Maxim DS1307 I2C RTC IC (code)
 *  @file rtc_ds1307.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016
 *  @note user RAM is not handled 
 *  @note peripherals used: I2C @ref rtc_ds1307_i2c, GPIO & timer @ref rtc_ds1307_square_wave_timer
 */

/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdio.h> // standard I/O facilities
#include <stdlib.h> // general utilities

/* STM32 (including CM3) libraries */
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/i2c.h> // I2C library
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/stm32/timer.h> // timer utilities

#include "global.h" // global utilities
#include "rtc_ds1307.h" // RTC header and definitions

#if defined(RTC_DS1307_SQUARE_WAVE_TICKS)
volatile uint32_t rtc_ds1307_ticks = 0;
volatile bool rtc_ds1307_tick_flag = false;
#endif

void rtc_ds1307_setup(void)
{
	// configure I2C peripheral (see RM008 26.3.3, I2C master)
	rcc_periph_clock_enable(RTC_DS1307_I2C_PORT_RCC); // enable clock for I2C I/O peripheral
	gpio_set_mode(RTC_DS1307_I2C_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, RTC_DS1307_I2C_PIN_SDA | RTC_DS1307_I2C_PIN_SCL); // setup I2C I/O pins
	rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function
	rcc_periph_clock_enable(RTC_DS1307_I2C_RCC); // enable clock for I2C peripheral
	i2c_reset(RTC_DS1307_I2C); // reset configuration
	i2c_peripheral_disable(RTC_DS1307_I2C); // I2C needs to be disable to be configured
	i2c_set_clock_frequency(RTC_DS1307_I2C, rcc_apb1_frequency/1E6); // configure the peripheral clock to the APB1 freq (where it is connected to)
	i2c_set_standard_mode(RTC_DS1307_I2C); // the DS1307 has a maximum I2C SCL freq if 100 kHz (corresponding to the standard mode)
	i2c_set_ccr(RTC_DS1307_I2C, rcc_apb1_frequency/(100E3*2)); // set Thigh/Tlow to generate frequency of 100 kHz
	i2c_set_trise(RTC_DS1307_I2C, rcc_apb1_frequency/1E6); // max rise time for 100 kHz is 1000 ns (~1 MHz)
	i2c_peripheral_enable(RTC_DS1307_I2C); // enable I2C after configuration completed

#if defined(RTC_DS1307_SQUARE_WAVE_TICKS)
	// setup timer to generate tick from square wave output
	rcc_periph_clock_enable(RTC_DS1307_SQUARE_WAVE_GPIO_RCC); // enable clock for GPIO peripheral
	gpio_set_mode(RTC_DS1307_SQUARE_WAVE_GPIO_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, RTC_DS1307_SQUARE_WAVE_GPIO_PIN); // set pin as input
	gpio_set(RTC_DS1307_SQUARE_WAVE_GPIO_PORT, RTC_DS1307_SQUARE_WAVE_GPIO_PIN); // enable pull-up
	rcc_periph_clock_enable(RTC_DS1307_SQUARE_WAVE_TIMER_RCC); // enable clock for timer peripheral
	timer_reset(RTC_DS1307_SQUARE_WAVE_TIMER); // reset timer state
	timer_ic_set_input(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TIMER_IC, RTC_DS1307_SQUARE_WAVE_TIMER_IN); // configure channel as input capture
	timer_ic_set_filter(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TIMER_IC, TIM_IC_OFF); // use no input capture filter
	timer_ic_set_polarity(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TIMER_IC, TIM_IC_FALLING); //capture on falling edge
	timer_slave_set_trigger(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TIMER_TS); // select trigger
	timer_slave_set_mode(RTC_DS1307_SQUARE_WAVE_TIMER, TIM_SMCR_SMS_ECM1); // select external clock more 1 as input
	timer_ic_enable(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TIMER_IC); // enable input capture   
	timer_set_mode(RTC_DS1307_SQUARE_WAVE_TIMER, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
	timer_set_prescaler(RTC_DS1307_SQUARE_WAVE_TIMER, 0); // no need to prescale
	timer_set_period(RTC_DS1307_SQUARE_WAVE_TIMER, RTC_DS1307_SQUARE_WAVE_TICKS-1); // set the tick period
	timer_enable_irq(RTC_DS1307_SQUARE_WAVE_TIMER, TIM_DIER_UIE); // enable interrupt for timer
	nvic_enable_irq(RTC_DS1307_SQUARE_WAVE_TIMER_IRQ); // allow interrupt for timer
	rtc_ds1307_tick_flag = false; // reset RTC tick flag
	timer_enable_counter(RTC_DS1307_SQUARE_WAVE_TIMER); // enable timer to count ticks
	rtc_ds1307_write_square_wave(RTC_DS1307_SQUARE_WAVE_FREQUENCY); // set square wave output frequency
#endif
}

/** read memory from RTC IC
 *  @param[in] addr start address for memory to read
 *  @param[out] data buffer to store read memory
 *  @param[in] len number of byte to read from the memory
 *  @return if read succeeded
 */
static bool rtc_ds1307_read_memory(uint8_t addr, uint8_t* data, size_t len)
{
	bool to_return = false; // return if read succeeded
	if (data==NULL || len==0) { // verify there it data to be read
		goto error;
	}
	i2c_send_start(RTC_DS1307_I2C); // send start condition to start transaction
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_SB)); // wait until start condition is transmitted
	if (!(I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_MSL)) { // verify if in master mode
		goto error;
	}
	i2c_send_7bit_address(RTC_DS1307_I2C, RTC_DS1307_I2C_ADDR, I2C_WRITE); // select slave
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_ADDR)); // wait until address is transmitted
	if (!((I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_TRA))) { // verify we are in transmit mode (and read SR2 to clear ADDR)
		goto error;
	}
	i2c_send_data(RTC_DS1307_I2C, addr); // send memory address we want to read
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_TxE)); // wait until byte has been transmitted
	i2c_send_start(RTC_DS1307_I2C); // send restart condition to switch from write to read mode
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_SB)); // wait until start condition is transmitted
	i2c_send_7bit_address(RTC_DS1307_I2C, RTC_DS1307_I2C_ADDR, I2C_READ); // select slave
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_ADDR)); // wait until address is transmitted
	if ((I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_TRA)) { // verify we are in read mode (and read SR2 to clear ADDR)
		goto error;
	}
	for (size_t i=0; i<len; i++) { // read bytes
		if (i==len-1) { // prepare to sent NACK for last byte
			i2c_disable_ack(RTC_DS1307_I2C); // NACK received to stop slave transmission
			i2c_send_stop(RTC_DS1307_I2C); // send STOP after receiving byte
		} else {
			i2c_enable_ack(RTC_DS1307_I2C); // ACK received byte to continue slave transmission
		}
		while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_RxNE)); // wait until byte has been received
		data[i] = i2c_get_data(RTC_DS1307_I2C); // read received byte
	}
	to_return = true;
error:
	if (I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_BUSY) { // release bus if busy
		i2c_send_stop(RTC_DS1307_I2C); // send stop to release bus
	}
	while (I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_MSL); // wait until bus released (non master mode)
	return to_return;
}

bool rtc_ds1307_oscillator_disabled(void)
{
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read a single byte containing CH value
	return data[0]&0x80; // return CH bit value to indicate if oscillator is disabled
}

uint16_t rtc_ds1307_read_square_wave(void)
{
	uint16_t to_return = 0; // square wave frequency to return (in Hz)
	uint8_t data[1] = {0}; // to read data over I2C
	const uint16_t rtc_ds1307_rs[] = {1, 4096, 8192, 32768}; // RS1/RS0 values
	rtc_ds1307_read_memory(7, data, LENGTH(data)); // read a single byte containing control register
	if (data[0]&0x10) { // verify if the square wave is enabled (SQWE)
		to_return = rtc_ds1307_rs[data[0]&0x03]; // read RS1/RS0 and get value
	} else {
		to_return = 0; // square wave output is disabled
	}
	return to_return;
}

uint8_t rtc_ds1307_read_seconds(void)
{
	uint8_t to_return = 0; // seconds to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read a single byte containing seconds value
	to_return = ((data[0]&0x70)>>4)*10+(data[0]&0x0f); // convert BCD coding into seconds
	return to_return;
}

uint8_t rtc_ds1307_read_minutes(void)
{
	uint8_t to_return = 0; // minutes to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(1, data, LENGTH(data)); // read a single byte containing minutes value
	to_return = (data[0]>>4)*10+(data[0]&0x0f); // convert BCD coding into minutes
	return to_return;
}

uint8_t rtc_ds1307_read_hours(void)
{
	uint8_t to_return = 0; // hours to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(2, data, LENGTH(data)); // read a single byte containing hours value
	if (data[0]&0x40) { // 12 hour mode
		if (data[0]&0x02) { // PM
			to_return += 12; // add the 12 hours
		}
		to_return += ((data[0]&0x10)>>4)*10; // convert BCD coding into hours (first digit)
	} else {
		to_return = ((data[0]&0x30)>>4)*10; // convert BCD coding into hours (first digit)
	}
	to_return += (data[0]&0x0f); // convert BCD coding into hours (second digit)
	return to_return;
}

uint8_t rtc_ds1307_read_day(void)
{
	uint8_t to_return = 0; // day to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(3, data, LENGTH(data)); // read a single byte containing day value
	to_return = (data[0]&0x07); // convert BCD coding into days
	return to_return;
}

uint8_t rtc_ds1307_read_date(void)
{
	uint8_t to_return = 0; // date to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(4, data, LENGTH(data)); // read a single byte containing date value
	to_return = ((data[0]&0x30)>>4)*10+(data[0]&0x0f); // convert BCD coding into date
	return to_return;
}

uint8_t rtc_ds1307_read_month(void)
{
	uint8_t to_return = 0; // month to return
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(5, data, LENGTH(data)); // read a single byte containing month value
	to_return = ((data[0]&0x10)>>4)*10+(data[0]&0x0f); // convert BCD coding into month
	return to_return;
}

uint8_t rtc_ds1307_read_year(void)
{
	uint8_t data[1] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(6, data, LENGTH(data)); // read a single byte containing year value
	uint8_t to_return = ((data[0]&0xf0)>>4)*10+(data[0]&0x0f); // convert BCD coding into year
	return to_return;
}

uint8_t* rtc_ds1307_read_time(void)
{
	static uint8_t time[7] = {0}; // store time {seconds, minutes, hours, day, date, month, year}
	uint8_t data[7] = {0}; // to read data over I2C
	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read all time bytes
	time[0] = ((data[0]&0x70)>>4)*10+(data[0]&0x0f); // convert seconds from BCD
	time[1] = (data[1]>>4)*10+(data[1]&0x0f); // convert minutes from BCD
	time[2] = 0; // re-initialize hours
	if (data[2]&0x40) { // 12 hour mode
		if (data[2]&0x02) { // PM
			time[2] += 12; // add the 12 hours
		}
		time[2] += ((data[2]&0x10)>>4)*10; // convert BCD coding into hours (first digit)
	} else {
		time[2] = ((data[2]&0x30)>>4)*10; // convert BCD coding into hours (first digit)
	}
	time[2] += (data[2]&0x0f); // convert BCD coding into hours (second digit)
	time[3] = (data[3]&0x07); // convert BCD coding into days
	time[4] = ((data[4]&0x30)>>4)*10+(data[4]&0x0f); // convert BCD coding into date
	time[5] = ((data[5]&0x10)>>4)*10+(data[5]&0x0f); // convert BCD coding into month
	time[6] = ((data[6]&0xf0)>>4)*10+(data[6]&0x0f); // convert BCD coding into year
	return time;
}

/** write memory into RTC IC
 *  @param[in] addr start address for memory to be written
 *  @param[in] data buffer to for memory to be written
 *  @param[in] len number of byte to write into the memory
 *  @return if write succeeded
 */
static bool rtc_ds1307_write_memory(uint8_t addr, uint8_t* data, size_t len)
{
	bool to_return = false; // return if read succeeded
	if (data==NULL || len==0) { // verify there it data to be read
		goto error;
	}
	i2c_send_start(RTC_DS1307_I2C); // send start condition to start transaction
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_SB)); // wait until start condition is transmitted
	if (!(I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_MSL)) { // verify if in master mode
		goto error;
	}
	i2c_send_7bit_address(RTC_DS1307_I2C, RTC_DS1307_I2C_ADDR, I2C_WRITE); // select slave
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_ADDR)); // wait until address is transmitted
	if (!((I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_TRA))) { // verify we are in transmit mode (and read SR2 to clear ADDR)
		goto error;
	}
	i2c_send_data(RTC_DS1307_I2C, addr); // send memory address we want to read
	while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_TxE)); // wait until byte has been transmitted
	for (size_t i=0; i<len; i++) { // write bytes
		i2c_send_data(RTC_DS1307_I2C, data[i]); // send byte to be written in memory
		while (!(I2C_SR1(RTC_DS1307_I2C) & I2C_SR1_TxE)); // wait until byte has been transmitted
	}
	to_return = true;
error:
	if (I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_BUSY) { // release bus if busy
		i2c_send_stop(RTC_DS1307_I2C); // send stop to release bus
	}
	while (I2C_SR2(RTC_DS1307_I2C) & I2C_SR2_MSL); // wait until bus released (non master mode)
	return to_return;
}

bool rtc_ds1307_oscillator_disable(void)
{
	uint8_t data[1] = {0}; // to write CH value data over I2C
	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read seconds with CH value
	data[0] |= 0x80; // set CH to disable oscillator
	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with CH value
}

bool rtc_ds1307_oscillator_enable(void)
{
	uint8_t data[1] = {0}; // to write CH value data over I2C
	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read seconds with CH value
	data[0] &= 0x7f; // clear CH to enable oscillator
	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with CH value
}

bool rtc_ds1307_write_square_wave(uint16_t frequency)
{
	uint8_t data[1] = {0}; // to write control register value data over I2C
	switch (frequency) { // set RS1/RS0 based on frequency
		case 0:
			data[0] = 0;
			break;
		case 1:
			data[0] = 0|(1<<4);
			break;
		case 4096:
			data[0] = 1|(1<<4);
			break;
		case 8192:
			data[0] = 2|(1<<4);
			break;
		case 32768:
			data[0] = 3|(1<<4);
			break;
		default: // unspecified frequency
			return false;
	}
	return rtc_ds1307_write_memory(7, data, LENGTH(data)); // write current seconds with CH value
}

bool rtc_ds1307_write_seconds(uint8_t seconds)
{
	if (seconds>59) {
		return false;
	}
	uint8_t data[1] = {0}; // to read CH value data and write seconds value over I2C
	if (!rtc_ds1307_read_memory(0, data, LENGTH(data))) { // read seconds with CH value
		return false;
	}
	data[0] &= 0x80; // only keep CH flag
	data[0] |= (((seconds/10)%6)<<4)+(seconds%10); // encode seconds in BCD format
	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with previous CH value
}

bool rtc_ds1307_write_minutes(uint8_t minutes)
{
	if (minutes>59) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (((minutes/10)%6)<<4)+(minutes%10); // encode minutes in BCD format
	return rtc_ds1307_write_memory(1, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_hours(uint8_t hours)
{
	if (hours>24) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (((hours/10)%3)<<4)+(hours%10); // encode hours in BCD 24h format
	return rtc_ds1307_write_memory(2, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_day(uint8_t day)
{
	if (day<1 || day>7) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (day%8); // encode day in BCD format
	return rtc_ds1307_write_memory(3, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_date(uint8_t date)
{
	if (date<1 || date>31) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (((date/10)%4)<<4)+(date%10); // encode date in BCD format
	return rtc_ds1307_write_memory(4, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_month(uint8_t month)
{
	if (month<1 || month>12) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (((month/10)%2)<<4)+(month%10); // encode month in BCD format
	return rtc_ds1307_write_memory(5, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_year(uint8_t year)
{
	if (year>99) {
		return false;
	}
	uint8_t data[1] = {0}; // to write time value
	data[0] = (((year/10)%10)<<4)+(year%10); // encode year in BCD format
	return rtc_ds1307_write_memory(6, data, LENGTH(data)); // write time value on RTC
}

bool rtc_ds1307_write_time(uint8_t seconds, uint8_t minutes, uint8_t hours, uint8_t day, uint8_t date, uint8_t month, uint8_t year)
{
	uint8_t data[7] = {0}; // to write all time values
	// seconds
	if (seconds>59) {
		return false;
	}
	if (!rtc_ds1307_read_memory(0, data, 1)) { // read seconds with CH value
		return false;
	}
	data[0] &= 0x80; // only keep CH flag
	data[0] |= (((seconds/10)%6)<<4)+(seconds%10); // encode seconds in BCD format
	// minutes
	if (minutes>59) {
		return false;
	}
	data[1] = (((minutes/10)%6)<<4)+(minutes%10); // encode minutes in BCD format
	// hours
	if (hours>24) {
		return false;
	}
	data[2] = (((hours/10)%3)<<4)+(hours%10); // encode hours in BCD 24h format
	// day
	if (day<1 || day>7) {
		return false;
	}
	data[3] = (day%8); // encode day in BCD format
	// date
	if (date<1 || date>31) {
		return false;
	}
	data[4] = (((date/10)%4)<<4)+(date%10); // encode date in BCD format
	// month
	if (month<1 || month>12) {
		return false;
	}
	data[5] = (((month/10)%2)<<4)+(month%10); // encode month in BCD format
	// year
	if (year>99) {
		return false;
	}
	data[6] = (((year/10)%10)<<4)+(year%10); // encode year in BCD format

	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write time values on RTC
}

#if defined(RTC_DS1307_SQUARE_WAVE_TICKS)
/** timer interrupt service routine called when number of ticks have been received */
void RTC_DS1307_SQUARE_WAVE_TIMER_ISR(void)
{
    if (timer_get_flag(RTC_DS1307_SQUARE_WAVE_TIMER, TIM_SR_UIF)) { // overflow even happened
        timer_clear_flag(RTC_DS1307_SQUARE_WAVE_TIMER, TIM_SR_UIF); // clear flag
		rtc_ds1307_ticks++; // increment count
		rtc_ds1307_tick_flag = true; // update flag
    }
}
#endif