Protocol for Traffic Light Control
==================================

RS232 settings
--------------
Baudrate:     19200 Baud (or 9600 if jumper is installed)
Bits:         8 bits
Parity:       None
Stopbits:     1
Flow control: No

Communication Protocol
----------------------
Contents of control message to Traffic Light: "!" R Y G "#" (no spaces)
With:
"!" (0x21) = Start of Message
R          = Value for Red
Y          = Value for Yellow
G          = Value for Green
"#" (0x23) = End of Message

Value can be:
"0" (0x30) = Off
"1" (0x31) = On
"2" (0x32) = Blink

Traffic Light returns: "Y" or "N"
With:
"Y" (0x59) = Acknowledge
"N" (0x4E) = Negative Acknowledge

Note that the Traffic Light sends one "Y" after startup

As soon as an error is detected, a "N" is sent and the whole message must be re-sent