diff --git a/lib/rtc_dcf77.c b/lib/rtc_dcf77.c
new file mode 100644
index 0000000..ad4559c
--- /dev/null
+++ b/lib/rtc_dcf77.c
@@ -0,0 +1,110 @@
+/* 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
+}
+
+
diff --git a/lib/rtc_dcf77.h b/lib/rtc_dcf77.h
new file mode 100644
index 0000000..40dfc92
--- /dev/null
+++ b/lib/rtc_dcf77.h
@@ -0,0 +1,53 @@
+/* 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.h
+ *  @author King Kévin <kingkevin@cuvoodoo.info>
+ *  @date 2016
+ *  @note peripherals used: GPIO @ref rtc_dcf77_gpio, timer @ref rtc_dcf77_timer 
+ */
+#pragma once
+
+/** @defgroup rtc_dcf77_gpio output to enable DCF module and input to capture DCF signal
+ *  @{
+ */
+#define RTC_DCF77_ENABLE_RCC RCC_GPIOA /**< GPIO peripheral clock to enable the module */
+#define RTC_DCF77_ENABLE_PORT GPIOA /**< GPIO port to enable the module */
+#define RTC_DCF77_ENABLE_PIN GPIO2 /**< GPIO pinto enable the module */
+#define RTC_DCF77_SIGNAL_RCC RCC_GPIOA /**< GPIO peripheral clock to capture the DCF signal */
+#define RTC_DCF77_SIGNAL_PORT GPIOA /**< GPIO port to capture the DCF signal */
+#define RTC_DCF77_SIGNAL_PIN GPIO3 /**< GPIO pin to capture the DCF signal */
+#define RTC_DCF77_SIGNAL_EXTI EXTI3 /**< GPIO external interrupt to capture the DCF signal */
+#define RTC_DCF77_SIGNAL_IRQ NVIC_EXTI3_IRQ /**< GPIO line interrupt */
+#define RTC_DCF77_SIGNAL_ISR exti3_isr /**< GPIO line interrupt service routine */
+/** @} */
+
+/** @defgroup rtc_dcf77_timer timer to measure signal puls
+ *  @{
+ */
+#define RTC_DCF77_TIMER TIM4 /**< timer peripheral */
+#define RTC_DCF77_TIMER_RCC RCC_TIM4 /**< timer peripheral clock */
+#define RTC_DCF77_TIMER_MAX_TIME 2200 /**< the maximum time in ms the timer can count. DCF77 have pulses < 2s */
+/** @} */
+
+/** @brief set when time information has been received */
+extern volatile bool rtc_dcf77_time_flag;
+
+/** @brief setup DCF77 time receiver module */
+void rtc_dcf77_setup(void);
+/** @brief switch on DCF77 time receiver module */
+void rtc_dcf77_on(void);
+/** @brief switch off DCF77 time receiver module */
+void rtc_dcf77_off(void);