diff --git a/stm-firmware/button.c b/stm-firmware/button.c
index 0e402b3..6f0db95 100644
--- a/stm-firmware/button.c
+++ b/stm-firmware/button.c
@@ -20,10 +20,14 @@
 
 #include <stm32/stm32f4xx.h>
 #include <reflow-controller/button.h>
+#include <stm-periph/stm32-gpio-macros.h>
 #include <stm-periph/clock-enable-manager.h>
 #include <stdint.h>
+#include <cmsis/core_cm4.h>
+#include <reflow-controller/systick.h>
 
 static volatile uint64_t to_active_timestamp;
+static volatile enum button_state int_state;
 
 void button_init()
 {
@@ -32,10 +36,33 @@ void button_init()
 	BUTTON_PORT->PUPDR &= PUPDR_DELETE(BUTTON_PIN);
 	BUTTON_PORT->PUPDR |= PULLUP(BUTTON_PIN);
 
+	to_active_timestamp = 0ULL;
+	int_state = BUTTON_IDLE;
 
+	SYSCFG->EXTICR[1] |= 0x3;
+	EXTI->IMR |= (1U<<4);
+	EXTI->FTSR |= (1U<<4);
+	EXTI->FTSR |= (1U<<4);
+	NVIC_EnableIRQ(EXTI4_IRQn);
 }
 
-enum button_state button_read_event();
+enum button_state button_read_event()
+{
+	uint64_t time_delta;
+
+	if (BUTTON_PORT->IDR & (1U<<BUTTON_PIN)) {
+		return int_state;
+		int_state = BUTTON_IDLE;
+	} else {
+		time_delta = systick_get_global_tick() - to_active_timestamp;
+		if (time_delta >= BUTTON_LONG_ON_TIME_MS)
+			return BUTTON_LONG;
+		else if (time_delta >= BUTTON_SHORT_ON_TIME_MS)
+			return BUTTON_SHORT;
+		else
+			return BUTTON_IDLE;
+	}
+}
 
 void button_deinit()
 {
@@ -43,3 +70,23 @@ void button_deinit()
 	BUTTON_PORT->PUPDR &= PUPDR_DELETE(BUTTON_PIN);
 	rcc_manager_disable_clock(&RCC->AHB1ENR, BITMASK_TO_BITNO(BUTTON_RCC_MASK));
 }
+
+void EXTI4_IRQHandler(void)
+{
+	uint64_t time_delta;
+
+	/* Clear interrupts */
+	EXTI->PR = EXTI->PR;
+	__DSB();
+
+	if (BUTTON_PORT->IDR & (1U<<BUTTON_PIN)) {
+		time_delta = systick_get_global_tick() - to_active_timestamp;
+		if (time_delta >= BUTTON_SHORT_ON_TIME_MS && time_delta < BUTTON_LONG_ON_TIME_MS) {
+			int_state = BUTTON_SHORT_RELEASED;
+		} else if (time_delta >= BUTTON_LONG_ON_TIME_MS) {
+			int_state = BUTTON_LONG_RELEASED;
+		}
+	} else {
+		to_active_timestamp = systick_get_global_tick();
+	}
+}
diff --git a/stm-firmware/include/reflow-controller/button.h b/stm-firmware/include/reflow-controller/button.h
index e5a72b7..46d648d 100644
--- a/stm-firmware/include/reflow-controller/button.h
+++ b/stm-firmware/include/reflow-controller/button.h
@@ -21,7 +21,6 @@
 #ifndef __BUTTON_H__
 #define __BUTTON_H__
 
-#define BUTTON_ACTIVE_LEVEL 0
 #define BUTTON_PORT GPIOD
 #define BUTTON_RCC_MASK RCC_AHB1ENR_GPIODEN
 #define BUTTON_PIN 4
@@ -29,7 +28,7 @@
 #define BUTTON_SHORT_ON_TIME_MS 50
 #define BUTTON_LONG_ON_TIME_MS 800
 
-enum button_state {BUTTON_IDLE = 0, BUTTON_SHORT, BUTTON_LONG};
+enum button_state {BUTTON_IDLE = 0, BUTTON_SHORT_RELEASED, BUTTON_LONG_RELEASED, BUTTON_SHORT, BUTTON_LONG};
 
 void button_init();