= Robitronic Overview =
The Robitronic lap counter is an IR based lap counter that communicates using a serial protocol.  

= Connection Information =
To connect to the Robitronic lap counter you must open the COM port with the following settings:
 * 38400 Baud
 * 1 Stop Bit
 * Parity None
 * Length 8 bits

= Initialization =
After you have connected to the Robitronic lap counter you must initialize it for communications.  This is done with a simple command.

{{{
03 B9 01
}}}

After this has been sent the lap counter will respond with a 00 and then beginning transmitting lap information.  There are two know packet types that the lap counter will return, a packet when a car is detected and a periodic time packet.

There appears to be no delimiter character, packets begin with a byte representing the length of the packet.

= Car Detected Packet =

If a car is detected the lap counter will return a packet like the following:

{{{
0D BD 84 1E 08 00 00 E7 36 00 00 55 F9 
}}}

The breakdown of this packet is the following:

{{{ 
Byte 1 is the length of the packet including this byte 0D for car detected packets
Byte 2 is the checksum
Byte 3 is the type of packet, 84 if this has car information
Byte 4-5 represent the UID of the car in reverse byte order
Byte 6-7 unknown, 00 in examples given
Byte 8-11 are the seconds in thousandths of a second in reverse byte order
Byte 12 is the number of hits the lap counter detected
Byte 13 is the signal strength
}}}

There is no specific character used to represent the beginning or end of a packet, instead the protocol has the first byte of the packet set to the length of the packet including that byte.

= Time stamp packet =

Approximately every second the lap counter will send a packet with just the time stamp.  This pack can look like this:

{{{
0B 5C 83 9B 3A 00 00 14 D0 01 02 
}}}

The breakdown of this packet is the following:

{{{
Byte 1 is the length of the packet 0B in the case of just a time stamp
Byte 2 is a checksum
Byte 3 is the packet type, 83 in the case of time stamp only
Byte 4-7 is the seconds in reverse byte order in thousandths of a second
Bytes 8-11 are unknown but in example were always 14 D0 01 02
}}}