Why am I only receiving the first address byte? (I2C Protocol) Expecting the slave to ACKnowledge and return data, but it does not. This is my protocol. This is my Datasheet.

Also FYI I'm on an Arduino Fio but I am not inheriting the Arduino library.

#include &lt;avr/io.h&gt;
#include &lt;util/delay.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;uart.h&gt;
#include &lt;i2c_master.h&gt;

#define LED PB5

#define I2C_READ 0x5A

char buffer[1];

//char data[9];
uint16_t val = 0;
uint8_t status = 0;


void getVal()
{
  if(i2c_start(I2C_READ))
    {
        uart_puts("Start ");

        val = ((uint8_t)i2c_read_ack())&lt;&lt;8; 
        val |= i2c_read_ack();

    status = ((uint8_t)i2c_read_nack());

      i2c_stop();

    } else
  {
        uart_puts("Error");

        i2c_stop();
    }
}

int main(void)
{
  init_uart(57600);
  i2c_init();

  DDRB = _BV(5);

    for(;;)
    {

      getVal();

            itoa(status, buffer, 10); //convert decimal to string base 10
            uart_puts(buffer);

      PORTB = 0xFF;
      _delay_ms(500);
      PORTB = 0x00;
      _delay_ms(500);
    }
    return 0;   /* never reached */
}
(Acknowledging this is an old question.) The TI article &quot;Troubleshooting I2C Bus Protocol&quot;, suggests several common reasons for no ACK:
1. Timing
2. Missing / Unexpected SCL pulses
3. Incomplete 8 bit block
4. Missing Bytes
5. False slave address
6. Unsuccessful address change