Initiate the Wire library and join the I2C bus as a master or slave. This should normally be called only once. Slave mode is not supported yet

Wire.begin(address, scl, sda);
Wire.begin(address, scl, sda, *buffer, len);
address: the 7-bit slave address (optional); if not specified, join the bus as a master. For master device the default address is 0. scl: pin SCL. sda: pin SDA. buffer: pointer to memory buffer. In case of master device buffer is used for outgoing data; In case of slave device the half of buffer is used for incoming data and the second half is used for outgoing data. len: buffer size in bytes. nothingreturns error code. 0 means success.