FIRST Robotic Competition in Oregon: Coprocessor 20040923

Topics

Attendance

Jeff Rice - Scalawags
Terry Heath - PHS
Jane Brandenburg - PHS
Allen Brown - Scalawags
Asumu Takikawa - CV
Doug Edmonds - PHS
Sean Lavelle - CHS

And the following may have attended. I don't know their names well enough to be sure.

Ray Cochran - PHS
Wyatt Fluckiger - PHS
Dave Brim - PHS

The state diagram wasn't quite right, so we spent the meeting developing it. In the process we made a few modifications to the protocol either to make the state diagram cleaner, or in anticipation of the coding process. Or simply because it felt better with the change. :-) I think the resulting protocol definition

Unfortunately I forgot to ask the status on the breaker reset time. This will remain on the AI list.

Packet Definition

Byte#	What	Comment
1	Start	Always '$'.
3	Dest	This is the node number of the destination device.
2	Src	This is the node number of the sourcing device.
4	Commands	This is one or more commands. See the command table
n-2	End	Always '\n'.
n-1	CKSUM1	High Nibble of the Checksum
n	CKSUM0	Low Nibble of the Checksum

Changes made to the table above:

Dest moved to before Src. This is so the packet can be forwarded sooner.
CKSUM moved after End. Makes state machine easier to write.
Commands defn more clearly deferred to the command table.

Command Table

Message Name	Char Length	Mess. Char [1st byte]	Mod. Char	Time	Len.	Data Chars	Comments
WRITE	4	1	Addr: [0-F]	-	-	[0-F] [0-F]	Write one byte of decoded data to the port.
READ	2	2	Addr: [0-F]	-	-	-	Request read from specified port.
DATAIS	4	3	Addr: [0-F]	-	-	[0-F] [0-F]	The value of the requested port is supplied as data. This is the reply to a 'READ' message.
CONFIGWR	4	4	Addr: [0-F]	-	-	[0-F] [0-F]	Write configuration for port X. Data byte following is mode, where 1 bits are OUTPUT and 0 bits are input.
CONFIGRD	2	5	Addr: [0-F]	-	-	-	Read configuration for port X. No data following. Port config byte is returned in a reply message.
CONFIGIS	4	6	Addr: [0-F]	-	-	[0-F] [0-F]	Read configuration reply from port X. This is the reply to a CONFIGRD message.
-	-	[7-9A-D]	-	-	-	-	not used.
PERIODIC	>=6	E	Addr: [0-F]	[0-F] [0-F]	[0-F] [0-F]	any even number of [0-F]	Set a periodic process. The time field is delay in milliseconds, high nibble first. The data field contains twice the number of nibbles specified by "length". That field is treated as a message that is processed at an interval specified by the time value. A periodic process X can be cancelled by sending it a zero length process string. Example: E50000
ERROR	>6	F	Level: [0-F]	-	[0-F] [0-F]	any even number of [0-F]	Error report or other message to be logged or reported to humans.

For example, if the packet was:

$12D51A02122059\n

$ - Start Packet
2 - Node 2, the manifold, is to receive this packet.
1 - Node 1, the LinkSys, sends this packet.
E - This is a PERIODIC message type.
5 - PERIODIC message slot 5.
1A - Time period in hexadecimal milliseconds. 26ms.
02 - Length
1220 - Data to be packetized and executed periodically.
- 1 - Node 1, the LinkSys, sends this packet.
- 2 - Node 2, the manifold, is to receive this packet.
- 2 - READ message.
- 0 - Port 0.
\n - End Packet.
59 - Checksum. (I didn't really calculate the checksum here.)

Changes made to the table above:

LOG and ERROR commands merged into the LOG command. Additional field added to distinguish between them.
ADDR field removed from LOG/ERROR command.

Jeff's picture of the Packet Parsing state diagram:

Asumu's picture of the Command Parsing state diagram:

Action Items before next week

Re-write BNF for the protocol, incorporating changes. -- Asumu
Draw state diagram for the command parser. -- Asumu
Merge the state diagrams for the packet parser and the CRC checker. -- Jeff
Determine breaker reset time. -- (Who was assigned this?)
Logins to scalawags.org. -- Gary

Schedule

Sept 30 - location: Corvallis High School
- Architect the communications protocol software.
- Define the tests for each module.
- Assign coding for the various modules.
- How long is breaker reset time?
Oct 7 - location: Corvallis High School
- Code Reviews.
- Discuss how to optimize FRC code.
Oct 14 - location: ?
- Optimize FRC code.
- What filesystems on laptop?

Last modified 11 Dec 2006
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