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

Make AVR Examples/Chapter13_Advanced-PWM-Tricks/arpeggiator/arpeggiator.c

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+/* 
+ *  "Algorithmic Symphonies"
+ *  When you combine modula arithmetic with a counter variable, 
+ *   you can get sequences that sound like 4-bit chiptunes.
+ *  Note that we're just outputting numerical values
+ *   directly as a voltage.  
+ *  Play around with these formulas defined here, or see others
+ *  in the attached file "music_formula_collection.txt".
+ * */
+
+// ------- Preamble -------- //
+#include <avr/io.h>		/* Defines pins, ports, etc */
+#include <util/delay.h>		/* Functions to waste time */
+#include <avr/power.h>
+#include "pinDefines.h"
+#include "macros.h"
+
+static inline void initTimer0(void){
+
+  set_bit(TCCR0A, COM0A1);	/* PWM output on OCR0A */
+  set_bit(SPEAKER_DDR, SPEAKER); /* enable output on pin */
+  set_bit(TCCR0A, WGM00);	/* Fast PWM mode */
+  set_bit(TCCR0A, WGM01);	/* Fast PWM mode, pt.2 */
+  set_bit(TCCR0B, CS00);	/* Clock with /1 prescaler */
+}
+
+static inline void pollButton(void){
+  if (bit_is_clear(BUTTON_PIN, BUTTON)) {
+    set_bit(SPEAKER_DDR, SPEAKER); /* enable output on pin */
+    clear_bit(LED_PORT, LED0);
+  }
+  else {
+    clear_bit(SPEAKER_DDR, SPEAKER); /* disable output on pin */
+    set_bit(LED_PORT, LED0);
+  }
+}
+
+int main(void){
+  uint16_t t=0;  
+
+  // -------- Inits --------- //
+  clock_prescale_set(clock_div_1);                  /* CPU clock 8 MHz */
+  initTimer0();
+   
+  set_bit(BUTTON_PORT, BUTTON);	/* pullup on button */
+
+  set_bit(LED_DDR, LED0);	/* LED on for diagnostics */
+  set_bit(LED_PORT, LED0);
+  _delay_ms(100);
+  clear_bit(LED_PORT, LED0);
+   
+  set_bit(SPEAKER_DDR, SPEAKER);
+  OCR0A = 210;
+  // ------ Event loop ------ //
+  while(1){	
+    
+    t++;
+	OCR0A = (uint8_t) ((t<<1)^((t<<1)+(t>>7)&t>>12))|t>>(4-(1^7&(t>>19)))|t>>7; /* "crowd" */ 
+	// OCR0A = (uint8_t) t;		  /* sawtooth */
+	// OCR0A = (uint8_t) t * (t >> 8);	/* rising pitch + aliases all over */
+	// OCR0A = (uint8_t) t & (t >> 8);     /* arpeggios */
+	// OCR0A = (uint8_t) t*( 42 & t >> 10 );  
+	// OCR0A = (uint8_t)  t*(t>>((t>>9)|(t>>8))&(63&(t>>4))); /* space invaders vs pong */
+	// OCR0A = (uint8_t) t*(t>>8*((t>>15)|(t>>8))&(20|(t>>19)*5>>t|(t>>3)));
+	// OCR0A = (uint8_t) (t*5&t>>7)|(t*3&t>>10);
+	// OCR0A = (uint8_t) (t*9 & t>>4 | t* 5 & t>> 7 | t * 3 & t/1024)-1; 
+	// OCR0A = (uint8_t) (t>>5)|(t>>4)|((t%42)*(t>>4)|(0x15483113)-(t>>4))/(t>>16)^(t|(t>>4)); 
+	// OCR0A = (uint8_t) t*(( (t>>12) | (t>>8)) & (63 & (t>>4)) );		  /* glitchy */
+    pollButton();
+    _delay_us(124);		/* Aiming for 8kHz sample rate */
+    
+  } /* End event loop */
+  return 0;		      /* This line is never reached  */
+}
+
+
+
+