Adds binary data to the packet to send over LoRaWAN. 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.
modem.write(val)
modem.write(str)
modem.write(buf, len)
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 length of the buffer