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

Make AVR Examples/Chapter07_Analog-to-Digital-Conversion-I/lightSensor/lightSensor.c

@@ -0,0 +1,41 @@
+// Quick Demo of light sensor
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include <util/delay.h>
+#include "pinDefines.h"
+
+// -------- Functions --------- //
+static inline void initADC0(void) {
+  ADMUX |= (1 << REFS0);                  /* reference voltage on AVCC */
+  ADCSRA |= (1 << ADPS2);                   /* ADC clock prescaler /16 */
+  ADCSRA |= (1 << ADEN);                                 /* enable ADC */
+}
+
+int main(void) {
+
+  // -------- Inits --------- //
+  uint8_t ledValue;
+  uint16_t adcValue;
+  uint8_t i;
+
+  initADC0();
+  LED_DDR = 0xff;
+
+  // ------ Event loop ------ //
+  while (1) {
+
+    ADCSRA |= (1 << ADSC);                     /* start ADC conversion */
+    loop_until_bit_is_clear(ADCSRA, ADSC);          /* wait until done */
+    adcValue = ADC;                                     /* read ADC in */
+                        /* Have 10 bits, want 3 (eight LEDs after all) */
+    ledValue = (adcValue >> 7);
+                                   /* Light up all LEDs up to ledValue */
+    LED_PORT = 0;
+    for (i = 0; i <= ledValue; i++) {
+      LED_PORT |= (1 << i);
+    }
+    _delay_ms(50);
+  }                                                  /* End event loop */
+  return 0;                            /* This line is never reached */
+}