def get_char_size(baudrate):
    """ Get the size of 1 character in seconds.

    From the implementation guide:

        "The implementation of RTU reception driver may imply the management of
        a lot of interruptions due to the t 1.5  and t 3.5  timers. With high

        communication baud rates, this leads to a heavy CPU load. Consequently
        these two timers must be strictly respected when the baud rate is equal
        or lower than 19200 Bps. For baud rates greater than 19200 Bps, fixed
        values for the 2 timers should be used:  it is recommended to use a
        value of 750us for the inter-character time-out (t 1.5) and a value of
        1.750ms for inter-frame delay (t 3.5)."
    """
    if baudrate <= 19200:
        return 11 / baudrate
    return 0.0005
