Method beginTransmission

Sming/Libraries/I2Cdev/I2Cdev.cpp:748–766

added by Jeff Rowberg 2013-05-07: Arduino Wire-style "beginTransmission" function (takes 7-bit device address like the Wire method, NOT 8-bit: 0x68, not 0xD0/0xD1)

    // Arduino Wire-style "beginTransmission" function
    // (takes 7-bit device address like the Wire method, NOT 8-bit: 0x68, not 0xD0/0xD1)
    byte Fastwire::beginTransmission(byte device) {
        byte twst, retry;
        retry = 2;
        do {
            TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO) | (1 << TWSTA);
            if (!waitInt()) return 1;
            twst = TWSR & 0xF8;
            if (twst != TW_START && twst != TW_REP_START) return 2;

            //Serial.print(device, HEX);
            //Serial.print(" ");
            TWDR = device << 1; // send device address without read bit (1)
            TWCR = (1 << TWINT) | (1 << TWEN);
            if (!waitInt()) return 3;
            twst = TWSR & 0xF8;
        } while (twst == TW_MT_SLA_NACK && retry-- > 0);
        if (twst != TW_MT_SLA_ACK) return 4;
        return 0;
    }

    byte Fastwire::writeBuf(byte device, byte address, byte *data, byte num) {
        byte twst, retry;