Reverse Engineer Inova Lightlink Wallboard

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Re: Reverse Engineer Inova Lightlink Wallboard

Postby merlinn31 » September 19th, 2014, 12:54 pm

This is all great stuff. One more question before I dig in too much: How much of a voltage swing should I see when typing into Putty?
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby bandersnatch » September 19th, 2014, 1:13 pm

merlinn31 wrote:This is all great stuff. One more question before I dig in too much: How much of a voltage swing should I see when typing into Putty?

No idea ;^)))
This depends on the specific RS232 interface in your computer. The standard allows anything between +3...+15v / -3...-15v
but the actual voltages vary wildly in the field.
The multimeter idea is just to get an indication of "something" there.
You are actually measuring a +/- stream of irregular pulses.
Set your multimeter to AC, low voltage and measure between Gnd and the jumpered RxData-TxData pins
when using the "null modem" cable to check that characters typed in putty are echoec back to putty.
This will give you an idea of the reading you should get from the correct TxData pin after you remove
the RxData-TxData jumper and measure pin 2 then pin 3 while typing in putty.
The correct TxData pin should show the same value you got before. and this value should change when
you stop and start typing
Rxdata will never change...

In summary: 3 steps
- Make a "null modem" cable and check that putty echoes back
- Remove the RxData-TxData jumper and find the "true" TxData pin
- Wire TxData to MAX232 pin 13 and experiment with RxData on MAX232 pin 14 or pin 7
- If you receive wierd characters then play with the Baudrate, Databits, stopbits, or parity settings in putty

Get stuck in!!! ;^)))
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby merlinn31 » September 20th, 2014, 4:01 pm

So maybe some progress... I looked at the Null Modem pinout that you linked and I found I had a null modem adapter lying around. Just to be safe, I ran a multimeter against all the pins to make sure it matched up with the table on the website and it did.

So I noticed that when I connected the ground pin, I didn't get any echo feedback. When I connect the Tx to pin 13 and watch Rx on pin 14 of the Max232 and the sign is powered off, putty echoes correctly. When I power the sign on and type some things in, the characters don't show up correctly anymore. If I hold "a" for example, I'll see a string of "A's" followed by erratic "@'s" and "'s". To switch it up, I moved the Rx from Max232 pin 14 to pin 7 and I get the exact same behavior.

My sign displays serial settings the same as shown in this pic: http://i.ebayimg.com/00/s/MTIwMFgxNjAw/ ... d/$_57.JPG

I don't know what S is, I'm assuming parity is Space, so my putty settings are 9600, 8, 1, space parity, no flow control.

No bootup messages are visible. Additionally, after looking up some specs about my Voltmeter, I'm wondering if the sample rate is too slow to pick up large swings in Voltage (1 sample / sec). I get .02-.06 volt shifts coming straight out of my laptop, and I see similar volt shifts coming out of 14 and 7 on the Max232.

No idea where to go from here. Weird that I get the predictable erratic behavior from both receive pins when banging on the keyboard. Is it ever the case that a Max232 chip isn't used for serial communication? :?: :?:

Edit: Switched baud settings to 1200 despite what the sign tells me when booting up. Now I successfully get data echoed back to me via putty correctly, but still no response from the sign when I do so.
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby bandersnatch » September 20th, 2014, 10:28 pm

Kool to hear that you have made progress.
Just one question. Have you disconnected the pin2-pin3 connection on your null modem cable?
This jumper is ONLY for testing that putty is working. You must remove it when connecting to the wallboard
or the serial comms will get confused.

If you have disconnected the pin2-pin3 connection and are getting wierd characters from the board
then this is great, 'cos the board isat least sending something.
You then need to play with comms settings, step-by-step until you find the right settings.
Not sure if putty has a "hex" display mode but you should definitely check the ascii values of the "wierd" characters being received.
It is possible that the comms settings are correct and you are actually receiving (non-printable) ACK/NAK ascii characters..
Possibly log the putty traffic to a file and check the input with a hex editor
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby merlinn31 » September 20th, 2014, 10:50 pm

Clarification:

Laptop connected to Null modem cable connected to Nothing: Putty shows nothing
Laptop connected to Null modem cable bridged Tx/Rx pins: Putty shows proper echo
Laptop connected to Null modem cable unbridged connected to Tx/Rx pins on Max232: Putty at 1200 echos keypresses

Sign doesn't respond to anything on the keyboard, no status messages on boot. The sign doesn't send any messages, I'm only getting the signals back that I'm sending. Is it possible that the serial port has been disabled somehow?
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby bandersnatch » September 21st, 2014, 11:30 am

merlinn31 wrote:Clarification:

Laptop connected to Null modem cable connected to Nothing: Putty shows nothing
Laptop connected to Null modem cable bridged Tx/Rx pins: Putty shows proper echo
Laptop connected to Null modem cable unbridged connected to Tx/Rx pins on Max232: Putty at 1200 echos keypresses

Sign doesn't respond to anything on the keyboard, no status messages on boot. The sign doesn't send any messages, I'm only getting the signals back that I'm sending. Is it possible that the serial port has been disabled somehow?


Hmmm...
".. Laptop connected to Null modem cable unbridged connected to Tx/Rx pins on Max232: Putty at 1200 echos keypresses.."
This would indicate either:
1/ the the board is echoing your keypresses back to your computer
- Kool 'cos this means the board is swallowing serial data and sending it back...
- Confirm this by checking that it ONLY works at 1200 baud
- If so, play with the databits, stop bits and parity settings to see if the response changes.
Only ONE configuration of Baud Rate, databits, stop bits and parity settings should work correctly
Then write a simple program to send all ascii characters to the board.
One after another followed by CR, or LF or CR+LF
and log the values echoed by the board
i.e. Send
0X0 0xD & log response
0X0 0xA & log response
0X0 0xD 0xA & log response
0X1 0xD & log response
0X10xA & log response
0X1 0xD 0xA & log response
...
0XFF 0xD & log response
0XFF 0xA & log response
0XFF 0xD 0xA & log response

One of these sequences should get a repsonse (if only "NAK"= board says whaaat???)
The idea here is to try and deduce the protocol expected by the board.
Many serial protocols expect each packet to always start with a special character

It is also possible that the serial comms needs to be enabled in some fashion
but then one would not expect the port to echo characters sent...


2/ The Max232 is wired as a "null modem" (unlikely)
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby merlinn31 » September 21st, 2014, 2:18 pm

Note that I don't get any successful keyboard echoes if I connect ground to db9 pin 5. It doesn't matter what speed or port settings. Not sure what that means.

I'll throw a program together and start hammering at it with data and see if it barfs anything up.
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby merlinn31 » September 22nd, 2014, 9:16 pm

No luck. I wrote a program to iterate through every ascii value 1-255 followed by a carriage return and all it did was echo out everything I sent at it.

I think I suck at this.
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby bandersnatch » September 23rd, 2014, 2:29 am

merlinn31 wrote:No luck. I wrote a program to iterate through every ascii value 1-255 followed by a carriage return and all it did was echo out everything I sent at it.

I think I suck at this.


You are doing fine. Think about how far you have already come.
Finding out what doesn't work is also useful information.
This sort of investigative work is immensly frustrating & not easy, which is what makes it interesting.
Two (paraphrased) quotes:
Edison: "..Genius is 1% inspiration and 99% perspiration.."
Murphy (from Murphy's law fame): "..When you are standing up to your neck in sh*t, dont let your head hang down.."

This is the time where you need show some staying power & remain persistent.
Step back from the low-level stuff & look for a different approach:
- Try holding down CR when the unit powers up
- Look for jumpers to enable/disable RS232 comms
- Follow the Tx/Rx lines from the Max232 & find out where they go to
- Look for other possible serial connections (maybe you missed something)

- Repeat the test process on the network ports
- Use a port scanner to check for available ports
- Connect to all available ports & watch for http traffic..

Hit the thing with a large hammer (!) ... Won't help, but you'll feel MUCH better ;^))
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Re: Reverse Engineer Inova Lightlink Wallboard

Postby danolgb » September 29th, 2014, 6:53 pm

Let me know if you have any luck. I have access to a similar board and the person who manages it threw out the software last week. Inova focusses on support desk and has an ongoing subscription model for support. So, getting the software from them without a current support contract is impossible.
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