This is the only interface to the serial connection.

def _hm_send_msg(self, message):
        """This is the only interface to the serial connection."""
        try:
            serial_message = message
            self.conn.write(serial_message)   # Write a string
        except serial.SerialTimeoutException:
            serror = "Write timeout error: \n"
            sys.stderr.write(serror)
        # Now wait for reply
        byteread = self.conn.read(159)
        # NB max return is 75 in 5/2 mode or 159 in 7day mode
        datal = list(byteread)
        return datal