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

Make AVR Examples/Chapter13_Advanced-PWM-Tricks/fatSaw/fatSaw.h

@@ -0,0 +1,36 @@
+
+// ------- Preamble -------- //
+#include <avr/io.h>		/* Defines pins, ports, etc */
+#include <util/delay.h>		/* Functions to waste time */
+#include <avr/interrupt.h>	
+#include <avr/power.h>
+#include "pinDefines.h"
+#include "macros.h"
+#include "fullSaw15.h"
+
+#define BASEPITCH       220 /* in tuningWord steps, which are ~1/2 Hz */
+#define PHASE_RATE      7   /* controls speed of phasing effect */
+
+#define NUMBER_OSCILLATORS  4
+/* 2 and 4 work just fine.
+   8 and 16 take too long to maintain our 31.25kHz sample rate
+   so the pitch shifts downwards and there's all sorts of aliasing.  
+   If you're just after scary sounds, 8 and 16 are awesome, but you may want 
+   to increase the BASEPITCH to compensate. */
+
+#define  OSCILLATOR_SHIFT   2
+/* This is the number of bits to shift when volume mixing. 
+   2**OSCILLATOR_SHIFT = NUMBER_OSCILLATORS 
+   If you don't change this to match the number of oscillators, you'll
+   get clipping and digital distortion.  */
+
+
+static inline void initTimer0(void){
+  set_bit(TCCR0A, WGM00);	/* Fast PWM mode */
+  set_bit(TCCR0A, WGM01);	/* Fast PWM mode */
+
+  set_bit(TCCR0A, COM0A1);	/* PWM output on OCR0A */
+  set_bit(SPEAKER_DDR, SPEAKER); /* enable output on pin */
+
+  set_bit(TCCR0B, CS00);	/* Clock with /1 prescaler */
+}