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

Make AVR Examples/Chapter17_I2C/i2cThermometer/i2cThermometer.c

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+                /* Reads LM75 Thermometer and Prints Value over Serial */
+
+// ------- Preamble -------- //
+#include <avr/io.h>
+#include <util/delay.h>
+#include <avr/power.h>
+
+#include "pinDefines.h"
+#include "USART.h"
+#include "i2c.h"
+
+// -------- Defines -------- //
+
+#define LM75_ADDRESS_W               0b10010000
+#define LM75_ADDRESS_R               0b10010001
+#define LM75_TEMP_REGISTER           0b00000000
+#define LM75_CONFIG_REGISTER         0b00000001
+#define LM75_THYST_REGISTER          0b00000010
+#define LM75_TOS_REGISTER            0b00000011
+// -------- Functions --------- //
+
+int main(void) {
+
+  uint8_t tempHighByte, tempLowByte;
+
+  // -------- Inits --------- //
+  clock_prescale_set(clock_div_1);                             /* 8MHz */
+  initUSART();
+  printString("\r\n====  i2c Thermometer  ====\r\n");
+  initI2C();
+
+  // ------ Event loop ------ //
+  while (1) {
+                        /* To set register, address LM75 in write mode */
+    i2cStart();
+    i2cSend(LM75_ADDRESS_W);
+    i2cSend(LM75_TEMP_REGISTER);
+    i2cStart();                      /* restart, just send start again */
+                              /* Setup and send address, with read bit */
+    i2cSend(LM75_ADDRESS_R);
+                               /* Now receive two bytes of temperature */
+    tempHighByte = i2cReadAck();
+    tempLowByte = i2cReadNoAck();
+    i2cStop();
+
+    // Print it out nicely over serial for now...
+    printByte(tempHighByte);
+    if (tempLowByte & _BV(7)) {
+      printString(".5\r\n");
+    }
+    else {
+      printString(".0\r\n");
+    }
+
+                                                    /* Once per second */
+    _delay_ms(1000);
+
+  }                                                  /* End event loop */
+  return 0;                            /* This line is never reached */
+}