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

Make AVR Examples/Chapter17_I2C/loggingThermometer/i2c.c

@@ -0,0 +1,39 @@
+#include "i2c.h"
+
+void initI2C(void) {
+                                     /* set pullups for SDA, SCL lines */
+  I2C_SDA_PORT |= ((1 << I2C_SDA) | (1 << I2C_SCL));
+  TWBR = 32;   /* set bit rate (p.242): 8MHz / (16+2*TWBR*1) ~= 100kHz */
+  TWCR |= (1 << TWEN);                                       /* enable */
+}
+
+void i2cWaitForComplete(void) {
+  loop_until_bit_is_set(TWCR, TWINT);
+}
+
+void i2cStart(void) {
+  TWCR = (_BV(TWINT) | _BV(TWEN) | _BV(TWSTA));
+  i2cWaitForComplete();
+}
+
+void i2cStop(void) {
+  TWCR = (_BV(TWINT) | _BV(TWEN) | _BV(TWSTO));
+}
+
+uint8_t i2cReadAck(void) {
+  TWCR = (_BV(TWINT) | _BV(TWEN) | _BV(TWEA));
+  i2cWaitForComplete();
+  return (TWDR);
+}
+
+uint8_t i2cReadNoAck(void) {
+  TWCR = (_BV(TWINT) | _BV(TWEN));
+  i2cWaitForComplete();
+  return (TWDR);
+}
+
+void i2cSend(uint8_t data) {
+  TWDR = data;
+  TWCR = (_BV(TWINT) | _BV(TWEN));                  /* init and enable */
+  i2cWaitForComplete();
+}