def send_arduino(msg, serial_connection):
    """
    Send the *msg* over the *serial_connection*

    Adds a hexadecimal number of 6 bytes to the start of the message before
    sending it. "hello there" -> "0x000bhello there"

    Parameters
    ----------
    msg : str or bytes
        the message you want to send
    serial_connection : object
        the :code:`serial.Serial` object you want to use for sending
    """
    if not isinstance(msg, bytes):
        msg = str(msg).encode()
    length = '{0:#0{1}x}'.format(len(msg), 6).encode()
    data = length + msg
    serial_connection.write(data)
