ex01 mod04 not stable

module04/ex00/main.c

@@ -1,8 +1,43 @@
 #include "header.h"
 
+// 14.3.3 : alternate functions on port D
+// PD2 : - INT0 (External Interrupt 0 Input)
+//       - PCINT18 (Pin Change Interrupt 18)
+// 12.4 : Interrupt Vectors in ATmega328 and ATmega328P
+//       - INT0 : External Interrupt Request 0
 
-// led RGB D5 must turns on in a loop of colors using PWM
+typedef enum {
+    DOWN,
+    UP
+} State;
+volatile uint8_t button_state = UP;
+
+// Table 13-2 : interrupt types
+#define INT0_LOW		((0 << ISC01) | (0 << ISC01))
+#define INT0_LOGICAL	((0 << ISC01) | (1 << ISC01))
+#define INT0_FALLING	((1 << ISC01) | (0 << ISC01))
+#define INT0_RAISING	((1 << ISC01) | (1 << ISC01))
+
+// use interruption to change led1 state when button1 is pressed
 int main() {
+	MODE_OUTPUT(LED1);
+	CLEAR_ELEM(LED1);
+	MODE_INPUT(BUTTON1);
+    PULLUP_ON(BUTTON1);
+
+	SREG |= ENABLE_GLOBAL_INTERRUPT;
+
+    EIMSK = (1 << INT0);							// 13.2.2 : Enable INT0 interrupt (EIMSK – External Interrupt Mask Register)
+	EICRA = INT0_LOGICAL;							// Table 13-2 : trigger type (EICRA – External Interrupt Control Register A)
+
     while (1);
 }
 
+ISR(INT0_vect) {
+	_delay_ms(50);
+	button_state = (button_state == UP) ? DOWN : UP;
+	if (button_state == UP) {
+		TOGGLE_ELEM(LED1);
+	}
+	// EIFR = (1 << INTF0);							// 13.2.3 : clear flag, why ? i think it only indicates that a trigger event has occured
+}