This command sends a byte to the serial port USIF1.
The input parameter byte can be zero or any Python byte to send to the serial port USIF1.
The return value is a Python integer which is -1 if the timeout period has expired, 1 otherwise.
Example:
b = SER2.sendbyte(0x0d)
sends the byte 0x0d, that corresponds to <CR>, to the serial port USIF1 handling, assigning the return value to b.