Started following some tutorial on att85 usi. Downloaded example code from make avr book.

Make AVR Examples/Chapter08_Hardware-Interrupts/helloPinChangeInterrupt/helloPinChangeInterrupt.c

@@ -0,0 +1,39 @@
+     /* Demo using pin-change interrupts and in-ISR debouncing routine */
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include <util/delay.h>
+#include <avr/interrupt.h>
+#include "pinDefines.h"
+
+
+ISR(PCINT2_vect) {              /* Run every time button state changes */
+  if (bit_is_clear(BUTTON_PIN, BUTTON)) {
+    LED_PORT |= (1 << LED1);
+  }
+  else {
+    LED_PORT &= ~(1 << LED1);
+  }
+}
+
+void initPinChangeInterrupt18(void) {
+  PCICR |= (1 << PCIE2);        /* set pin-change interrupt for D pins */
+  PCMSK2 |= (1 << PCINT18);      /* set mask to look for PCINT18 / PD2 */
+  sei();                          /* set (global) interrupt enable bit */
+}
+
+int main(void) {
+  // -------- Inits --------- //
+  LED_DDR = 0xff;                                   /* all LEDs active */
+  BUTTON_PORT |= (1 << BUTTON);                              /* pullup */
+  initPinChangeInterrupt18();
+
+  // ------ Event loop ------ //
+  while (1) {
+
+    _delay_ms(200);
+    LED_PORT ^= (1 << LED0);
+
+  }                                                  /* End event loop */
+  return 0;                            /* This line is never reached */
+}