/* 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 get time from a DCF77 module (code)
 *  @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

/* 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;
volatile uint64_t rtc_dcf77_frame = 0; /**< the received DCF77 frame bits */

void rtc_dcf77_setup(void)
{
	// setup enable output
	rcc_periph_clock_enable(RTC_DCF77_ENABLE_RCC); // enable clock GPIO peripheral
	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
}

uint8_t* rtc_dcf77_time(void)
{
	static uint8_t to_return[6] = {0}; // arrays with date values to return
	uint8_t parity = 0; // to check parity
	if (rtc_dcf77_frame==0) { // no time received yet
		return NULL;
	}
	if (!(rtc_dcf77_frame&((uint64_t)1<<20))) { // start of encode time should always be 1
		return NULL;
	}
	// check minute parity
	parity = 0;
	for (uint8_t bit=21; bit<=28; bit++) {
		if (rtc_dcf77_frame&((uint64_t)1<<bit)) {
			parity++; // count the set bits
		}
	}
	if (parity%2) { // parity should be even
		return NULL;
	}
	to_return[0] = 1*((rtc_dcf77_frame>>21)&(0x1))+2*((rtc_dcf77_frame>>22)&(0x1))+4*((rtc_dcf77_frame>>23)&(0x1))+8*((rtc_dcf77_frame>>24)&(0x1))+10*((rtc_dcf77_frame>>25)&(0x1))+20*((rtc_dcf77_frame>>26)&(0x1))+40*((rtc_dcf77_frame>>27)&(0x1)); // read minute (00-59)
	if (to_return[0]>59) { // minutes should not be more than 59
		return NULL;
	}
	// check hour parity
	parity = 0;
	for (uint8_t bit=29; bit<=35; bit++) {
		if (rtc_dcf77_frame&((uint64_t)1<<bit)) {
			parity++; // count the set bits
		}
	}
	if (parity%2) { // parity should be even
		return NULL;
	}
	to_return[1] = 1*((rtc_dcf77_frame>>29)&(0x1))+2*((rtc_dcf77_frame>>30)&(0x1))+4*((rtc_dcf77_frame>>31)&(0x1))+8*((rtc_dcf77_frame>>32)&(0x1))+10*((rtc_dcf77_frame>>33)&(0x1))+20*((rtc_dcf77_frame>>34)&(0x1)); // read hour (00-23)
	if (to_return[1]>23) { // hours should not be more than 23
		return NULL;
	}
	// check date parity
	parity = 0;
	for (uint8_t bit=36; bit<=58; bit++) {
		if (rtc_dcf77_frame&((uint64_t)1<<bit)) {
			parity++; // count the set bits
		}
	}
	if (parity%2) { // parity should be even
		return NULL;
	}
	to_return[2] = 1*((rtc_dcf77_frame>>36)&(0x1))+2*((rtc_dcf77_frame>>37)&(0x1))+4*((rtc_dcf77_frame>>38)&(0x1))+8*((rtc_dcf77_frame>>39)&(0x1))+10*((rtc_dcf77_frame>>40)&(0x1))+20*((rtc_dcf77_frame>>41)&(0x1)); // read day of the month (01-31)
	if (to_return[2]==0 || to_return[2]>31) { // day of the month should be 1-31
		return NULL;
	}
	to_return[3] = 1*((rtc_dcf77_frame>>42)&(0x1))+2*((rtc_dcf77_frame>>43)&(0x1))+4*((rtc_dcf77_frame>>44)&(0x1)); // read day of the week (1=Monday - 7=Sunday)
	if (to_return[3]==0 || to_return[3]>7) { // day of the week should be 1-7
		return NULL;
	}
	to_return[4] = 1*((rtc_dcf77_frame>>45)&(0x1))+2*((rtc_dcf77_frame>>46)&(0x1))+4*((rtc_dcf77_frame>>47)&(0x1))+8*((rtc_dcf77_frame>>48)&(0x1))+10*((rtc_dcf77_frame>>49)&(0x1)); // read month of the year (01-12)
	if (to_return[4]==0 || to_return[4]>12) { // month of the year should be 1-12
		return NULL;
	}
	to_return[5] = 1*((rtc_dcf77_frame>>50)&(0x1))+2*((rtc_dcf77_frame>>51)&(0x1))+4*((rtc_dcf77_frame>>52)&(0x1))+8*((rtc_dcf77_frame>>53)&(0x1))+10*((rtc_dcf77_frame>>54)&(0x1))+20*((rtc_dcf77_frame>>55)&(0x1))+40*((rtc_dcf77_frame>>56)&(0x1))+80*((rtc_dcf77_frame>>57)&(0x1)); // read year of the century (00-99)
	if (to_return[5]>99) { // year should be <100
		return NULL;
	}
	return to_return;
}

/** interrupt service routine called when signal edge is detected, decoding the received DCF77 frame (composed by high pulses) */
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_edge = 0; // time on when the last pulse (rising edge) has been detected
	static uint64_t rtc_dcf77_frame_tmp = 0; // the DCF77 frame bits as they get filled
	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
		time = (uint32_t)(time-pulse_edge)*RTC_DCF77_TIMER_MAX_TIME/(1<<16); // get time since last rising edge (integer underflow possible)
		if (new_state) { // rising edge
			if (time < 980) { // glitch
				goto end; // ignore glitch
			} else if (time < 1030) { // a normal pulse
				pulse++; // go to next pulse
				if (pulse>58) { // something wrong happened
					pulse = 0; // restart
				}
			} else if (time < 1980) { // glitch
				goto end; // ignore glitch
			} else if (time < 2130) { // first pulse of a frame
				if (pulse==58) { // full frame received
					rtc_dcf77_frame = rtc_dcf77_frame_tmp; // save received complete frame
					rtc_dcf77_time_flag = true; // notify user
				}
				pulse = 0;
			} else { // something is wrong, restart
				pulse = 0;
			}
			pulse_edge = 0; // save new edge
			timer_set_counter(RTC_DCF77_TIMER, 0); // reset timer to count
		} else { // falling edge
			if (time < 90) { // glitch
				goto end; // ignore glitch
			} else if (time < 120) { // 0 received
				rtc_dcf77_frame_tmp &= ~((uint64_t)1<<pulse); // save 0 bit
			} else if (time < 190) { // glitch
				goto end; // ignore glitch
			} else if (time < 220) { // 1 received
				rtc_dcf77_frame_tmp |= ((uint64_t)1<<pulse); // save 1 bit
			}	
		}	
	}
end:
	old_state = new_state; // save new state
}