write a reference
Serial : serial port object. See the list of available serial ports for each board on the Serial main page.
val : a value to send as a single byte.
str : a string to send as a series of bytes.
buf : an array to send as a series of bytes.
len : the number of bytes to be sent from the array.
Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the print() function instead.