Writes data from a slave device in response to a request from a master, or queues bytes for transmission from a master to slave device (in-between calls to beginTransmission() and endTransmission()).
- value: a value to send as a single byte
- string: a string to send as a series of bytes
- data: an array of data to send as bytes
- length: the number of bytes to transmit
byte write() will return the number of bytes written, though reading that number is optional