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

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

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+/*
+bossButton.c
+
+As long as we've got a button wired up to the AVR,
+might as well have some fun.
+
+Upload this code to your AVR, run bossButton.py.
+Press button.
+
+*/
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include <util/delay.h>
+#include "pinDefines.h"
+#include "USART.h"
+
+static inline void blinkLED(void) {
+  LED_PORT = (1 << LED0);
+  _delay_ms(1000);
+  LED_PORT &= ~(1 << LED0);
+}
+
+
+int main(void) {
+
+  // -------- Inits --------- //
+  BUTTON_PORT |= (1 << BUTTON);          /* input mode, turn on pullup */
+
+  LED_DDR = (1 << LED0);
+  blinkLED();
+
+  initUSART();
+  transmitByte('O');
+
+  // ------ Event loop ------ //
+  while (1) {
+
+    if (bit_is_clear(BUTTON_PIN, BUTTON)) {
+      transmitByte('X');
+      blinkLED();
+    }
+
+  }                                                  /* End event loop */
+  return 0;
+}