I2C_REP_START

uint8_t i2c_start(uint8_t address)

{

    // reset TWI control register

    TWCR = 0;

    // transmit START condition

    TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);

    // wait for end of transmission

    while( !(TWCR & (1<<TWINT)) );

    // check if the start condition was successfully transmitted

    if((TWSR & 0xF8) != TW_START){ return 1; }

    // load slave address into data register

    TWDR = address;

    // start transmission of address

    TWCR = (1<<TWINT) | (1<<TWEN);

    // wait for end of transmission

    while( !(TWCR & (1<<TWINT)) );

    // check if the device has acknowledged the READ / WRITE mode

    uint8_t twst = TW_STATUS & 0xF8;

    if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;

    return 0;

}

    // transmit START condition

    TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);