/* 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/>.
 *
 */
/** @brief library to get time from a DCF77 module
 *  @file rtc_dcf77.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016
 *  @note peripherals used: GPIO @ref rtc_dcf77_gpio, timer @ref rtc_dcf77_timer 
 */

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

#include <stdio.h>

/* 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/spi.h> // SPI library
#include <libopencm3/stm32/timer.h> // timer library
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities

#include "rtc_dcf77.h" // RTC DCF77 library API
#include "global.h" // common methods

volatile bool rtc_dcf77_time_flag = false;

void rtc_dcf77_setup(void)
{
	// setup enable output
	rcc_periph_clock_enable(RTC_DCF77_ENABLE_RCC); // enable clock GPIO peripherial
	gpio_set_mode(RTC_DCF77_ENABLE_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, RTC_DCF77_ENABLE_PIN); // set pin to output push-pull to be able to enable the module
	rtc_dcf77_off(); // disable module at start

	// setup signal input
	rcc_periph_clock_enable(RTC_DCF77_SIGNAL_RCC); // enable clock for signal input peripheral
	gpio_set_mode(RTC_DCF77_SIGNAL_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, RTC_DCF77_SIGNAL_PIN); // set signal pin to input
	rcc_periph_clock_enable(RCC_AFIO); // enable alternate function clock for external interrupt
	exti_select_source(RTC_DCF77_SIGNAL_EXTI, RTC_DCF77_SIGNAL_PORT); // mask external interrupt of this pin only for this port
	exti_set_trigger(RTC_DCF77_SIGNAL_EXTI, EXTI_TRIGGER_BOTH); // trigger on both edges
	exti_enable_request(RTC_DCF77_SIGNAL_EXTI); // enable external interrupt
	nvic_enable_irq(RTC_DCF77_SIGNAL_IRQ); // enable interrupt

	// setup timer to measure pulses
	rcc_periph_clock_enable(RTC_DCF77_TIMER_RCC); // enable clock for timer peripheral
	timer_reset(RTC_DCF77_TIMER); // reset timer state
	timer_set_mode(RTC_DCF77_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_DCF77_TIMER, RTC_DCF77_TIMER_MAX_TIME*(rcc_ahb_frequency/1000)/(1<<16)); // set prescaler to count up to the maximum time
	timer_enable_counter(RTC_DCF77_TIMER); // start timer to measure time
}

void rtc_dcf77_on(void)
{
	gpio_clear(RTC_DCF77_ENABLE_PORT, RTC_DCF77_ENABLE_PIN); // enable module by pull pin low
}

void rtc_dcf77_off(void)
{
	gpio_set(RTC_DCF77_ENABLE_PORT, RTC_DCF77_ENABLE_PIN); // disable module by pull pin high
}

/** @brief interrupt service routine called when signal edge is detected */
void RTC_DCF77_SIGNAL_ISR(void)
{
	exti_reset_request(RTC_DCF77_SIGNAL_EXTI); // reset interrupt
	static uint16_t old_state = 0; // save last port state to detect difference
	static uint8_t pulse = 0; // next pulse number in the DCF77 frame
	//static uint16_t pulse_rising = 0, pulse_falling = 0; // time on when the last pulse edge has been detected
	static uint16_t pulse_rising = 0;
	uint16_t time = timer_get_counter(RTC_DCF77_TIMER); // get timer value

	uint16_t new_state = gpio_get(RTC_DCF77_SIGNAL_PORT, RTC_DCF77_SIGNAL_PIN); // save last port state to detect difference
	if (old_state!=new_state) { // pulse edge detected
		if (new_state) { // rising edge
			time = (uint32_t)(time-pulse_rising)*RTC_DCF77_TIMER_MAX_TIME/(1<<16); // get time since last rising edge (integer underflow possible)
			if (time < 900) { // ignore glitches
				goto end;
			} else if (time < 1100) { // a normal pulse
				pulse = (pulse+1)%59; // go to next pulse (there should be no more than 59)
			} else if (time < 1900) { // ignore glitch
				goto end;
			} else if (time < 2100) { // first pulse of a frame
				pulse = 0;
			} else { // something is wrong, restart
				pulse = 0;
			}
			led_toggle();
			pulse_rising = 0; // save new edge
			timer_set_counter(RTC_DCF77_TIMER, 0); // reset timer to count
			printf("%u\n", pulse);
		}
	}
end:
	old_state = new_state; // save new state
}