How to decode communication

[Christopher4187]

I have a device that uses wired communication and need to decode it, however, I don't know anything about the protocol. I've never done this before (attempted to decode data where I don't know the protocol) and I'm hoping someone can give me some pointers as to the most efficient method to figure it out.

Here is what I know:

1. It's for a little league football scoreboard.
2. It travels about 300 feet.
3. It's wired and there are two wires going to the scoreboard.
4. When I measured the wires with a DMM it is about 14.9 VDC.
5. The data appears to be PWM as data is constantly flowing whether a button is pushed or not.
6. The frequency appears to be approximately 1.6 kHZ and I can see the data using an oscilloscope.
7. There are a lot of 74HCxx's on the PCB.
8. I tried using hyperterminal and while I could see data nothing appeared to be valid data. The speed does appear to be around 4800 bps.
9. There is an RJ11 jack on the PCB but I don't know if this is used for the communication or not. I was taking measurements from another connector on the PCB.

That's pretty much all I know. This is an area where I have very little experience (data communication) so any pointers would be appreciated.

[Jerson]

You can start by making educated guesses by looking at the chips on the communication board. That will give clues to what is going on there. A photo of the board might help you get ideas here. It could be a current loop communication which was used to cover long distances before RS485 became the norm.

[Christopher4187]

I know the board was manufactured in 1998 by Daktronics. I don't have it with me but I will try to post a picture when I get home tonight. I'm stuck on two problems.

1. The constant data makes it hard for me to determine where the comms starts and ends.

2. The PWM (or at least that's what it appears to be) seems like it isn't steady. This could be my probe so I'll recheck it when I get home.

Maybe this will help.....maybe not. Here is a log from Hyperterminal. Most of it was automatically sent by the controller and I pushed a button five or six times during this log. I connected the output pin of the scoreboard to pin 2 of the Max232. I was using 4800 bps:

   $      	 @  	 @@    $    $      	 @      	 €     $     	 @  	 @  	 €     $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @@    $    $      	 @  	 @  	 €     $     	 @  	 @  	 €     $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $         $ 	 @  	 € 	 @  	 €  	 @  	 €          $    ’    $      	 @    @  	 @  	 @  	 @     	 	 @     $    $    $  @     $$	 @  	 @  	 @  	 @  	 @  	  $    	    $    $ 	 €       	 @    @  	 @  	 @     $    $      	 @  	 @H    $    $      	 @  	 @     $    $      	 @  	 @  	 €     $    $ 	 @  	 @  	 @     $$	  $ 	 @     $         $      	 €    @  	 @H $ @  	 @       	 @     $ 	 @     $   @I    $ 	 @  	 €  	 @  	 @  	 @  	 €       	 €     $$	 €       	 @I      	 @  	     	 @       	 €     $ 	 €     $ 	 @       	 @  	      	 @     $    $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @@    $    $      	 @  	 @  	 €     $     	 @  	 @  	 €     $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	 €     $    	 	 @  	 @  	 €     $    $ 	 @  	 @       	 €     $ ) €     $ 	 @I    ’ 	 @  	 € 	 @  	  $ 	 @     $         $   @  	 €    @  	 @H  @  	 @       	 @H    $ 	 @     $   @     $ 	 @  	 €  	 @  	 @  	 @  	 €       	 @  	 @     $    $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @$    $    $      	 @  	 @  	  $    $ 	 A     $ 	 @  	   	 @  	 €  	 @  	            $    ’    $   @  	 @    @  	 @  	 @  	 @      	 @     $    $    $  @@    $$	 @  	    	 @  	 @  	       $     	 @  	 @  	       $    $ 	 @  	 @  	       $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $ 	         	       $ 	       $$	 @I      	 @  	 * 	 @  	  $ 	 @     $         $      	      @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @       	 @       	 @  	   	 @     I 	 @     $         $   @     $ $ @  	 @  	 @  	 @       	 @     I 	 @  	 @  	 @     $    $ 	 @  	 @  	 @     $    $      	 €          $      	 @    @  	 @  	 @  	 @       	 @     $    $    $ $ @H  @  	 @  	       $    $ 	 @  	 @  	 @I    $    $      	 @  	 @H    $    $      	 @     $ 	 @H    $    I    $   @  	    	 @  	 @@ 	 @  	 @       	       $ 	       $ 	 @I    $    $      	 @  	 @@    $    $      	 @  	 @  	 €     $     	 @  	 @       	 @H    $ 	 @     $   @     $ 	 @  	 €  	 @  	 @  	 @  	 €       	 €     $H   $    ’      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $      	 @  	 @H    $    $      	 @  	 @     $    $      	 @  	 @  	       $    I 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $      	 @  	 @H    $    $      	 @  	 @  	       $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @H    $    $      	 @  	 @  	       $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @@    $    $      	 @  	 @  	       $     	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $      	 @  	 @H    $    $      	 @  	 @     $    $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @     $    $      	 @  	 @H    $    $      	 @  	 @  	       $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @H    $    $      	 @  	 @  	       $      	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @@         $      	 @  	 @  	       $     	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $ 	 @  	 @  	 @I    $    $      	 @  	 @     $    $      	 @  	 @  	       $    	 	 @  	 @  	       $    $ 	 @  	 @  	 @     $    $

[Christopher4187]

I can't get the code box to be any larger. It's missing the spaces but here is the data:

$ @ @@ $ $ @  € $
@ @ € $ $ @ @ @ $ $ @ @ @I $ $ @ @@ $ $ @ @ € $
@ @ € $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ $ @ €
@ € @ € $ ’ $ @ @ @ @ @ @ $ $ $  @ $$ @ @ @ @ @ $ $ $ € @ @ @ @ $ $ @ @H $ $ @ @ $ $ @ @ € $ $ @ @ @ $$ $ @ $ $ € @ @H $ @ @ @ $ @ $ @I $ @ € @ @ @ € € $$ € @I @
 @ € $ € $ @ @  @ $ $ $ @ @ @ $ $ @ @ @I $ $ @ @@ $ $ @ @ € $
@ @ € $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ @ @ € $ @ @ € $ $ @ @ € $ ) € $ @I ’ @ €
@ $ @ $ $ @ € @ @H  @ @ @H $ @ $ @ $ @ € @ @ @ € @ @ $ $ @ @ $ $ @ @ @ $ $ @ @ @$ $ $ @ @ $ $ A $ @
@ € @ $ ’ $ @ @ @ @ @ @
@ $ $ $  @@ $$ @ @ @ $
@ @ $ $ @ @ $ $ @ @ @I $ $ @ @ $ $ $$ @I @ *
@ $ @ $ $ @ @I $ $ @ @ $ $ @ @ $ @ @ $ $ @ @ @  @ I @ $ $ @ $ $ @ @ @ @ @ I @ @ @ $ $ @ @ @ $ $ € $ @ @ @ @ @ @ $ $ $ $ @H  @ @ $ $ @ @ @I $ $ @ @H $ $ @ $ @H $ I $ @ @ @@ @ @ $ $ @I $ $ @ @@ $ $ @ @ € $
@ @ @H $ @ $ @ $ @ € @ @ @ € € $H $ ’ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @H $ $ @ @ $ $ @ @ $ I @ @ $ $ @ @ @ $ $ @ @H $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @H $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @@ $ $ @ @ $
@ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @H $ $ @ @ $ $ @ @ $ $ @ @ @ $ $ @ @ @ $ $ @ @H $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @H $ $ @ @ $ @ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @@ $ @ @ $
@ @ $ $ @ @ @ $ $ @ @ @I $ $ @ @ $ $ @ @ $ @ @ $ $ @ @ @ $ $

[Dave]

Chris, Measure the time of the smallest pulse and that should be the the baudrate.

Dave Purola,

[Christopher4187]

I'll check it but it's either 2400 or 4800. When I figure out the exact baudrate, how can I decode the data?

[richard]

it could be a stream of data for 7 segment display array, that's updated 50 times a second . ie every bit represents a segment

[Christopher4187]

It actually worked! Some of my times are off a bit so the numbers looked a little funny but overall the comms works well. What I also found interesting is that the controller sent the data every 2.5mS but it's not even necessary. I sent it once and the numbers stayed on the scoreboard.

Thanks to all who helped.

[Art]

Sending the message constantly would reduce potential for noise interpreted as data interfering with the display too long,
but checksumming the message would better achieve that.