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

Make AVR Examples/Chapter06_Digital-Input/toggleButton_debounced/toggleButton_debounced.c

@@ -0,0 +1,42 @@
+/*
+   Demonstrates using state to detect button presses
+*/
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include "pinDefines.h"
+
+#include <util/delay.h>
+#define DEBOUNCE_TIME  5                               /* microseconds */
+
+uint8_t debouncePress(void) {
+  if (bit_is_clear(BUTTON_PIN, BUTTON)) {      /* button is pressed now */
+    _delay_ms(DEBOUNCE_TIME);
+    if (bit_is_clear(BUTTON_PIN, BUTTON)) {            /* still pressed */
+      return (1);
+    }
+  }
+  return 0;
+}
+
+int main(void) {
+  // -------- Inits --------- //
+  uint8_t buttonWasPressed=0;                                 /* state */
+  BUTTON_PORT |= (1 << BUTTON);     /* enable the pullup on the button */
+  LED_DDR = (1 << LED0);                      /* set up LED for output */
+
+  // ------ Event loop ------ //
+  while (1) {
+    if (debouncePress()) {
+      if (buttonWasPressed == 0) {     /* but wasn't last time through */
+        LED_PORT ^= (1 << LED0);                        /* do whatever */
+        buttonWasPressed = 1;                      /* update the state */
+      }
+    }
+    else {                                /* button is not pressed now */
+      buttonWasPressed = 0;                        /* update the state */
+    }
+
+  }                                                  /* End event loop */
+  return 0;                            /* This line is never reached */
+}