Is it an RS-232 compatibility issue?

Question

1.00/5 (1 vote)

See more:

I've been working on a VxWorks-based IPC. My mission is now to update S/W for changing touch panel, which is connected to the mother board through RS-232. According to relative data & original codes, what I need to update is from interpretation of touch panel's protocol. The old & new panel's baud rates are both 9600. But unfortunately, IPC can't even get characters from new touch panel correctly. Below are what I did as experimenting on old & new panels:

1. Coonect PC terminal tool to new panel: Panel sends packets to PC correctly.
2. Connect PC terminal tool to old panel: Panel sends packets to PC correctly.
3. Old panel connecting to IPC mother board: working fine.
4. Use scope to measure the pulse of signal from RS-232 of both panels: the voltage are the same.

From the above data, it seems that IPC should be able to receive character string from new panel. But the result is that IPC can't get character from the new panel. Is there anything I still missed to check? What makes IPC can't get characters from new panel?

What I have tried:

Discussed with my coworkers, googled it, posted to other group but was rejected and deleted.

Posted 24-May-17 17:53pm

Stan Huang

Updated 24-May-17 21:07pm

Add a Solution

2 solutions

Solution 2

Quote:
Coonect PC terminal tool to new panel: Panel sends packets to PC correctly.

Quote:
But the result is that IPC can't get character from the new panel

It looks the original program is not able to receive the (correctly sent) packets. It could be a protocol problem. check out the documentation of the old and new touch panel in order to clarify it.

Posted 24-May-17 21:07pm

CPallini

Comments

Stan Huang 25-May-17 3:39am

In my opinion, it's not protocol issue so far. There may be protocol issue, but it should come after character string are received. That is, even the original codes can't interpret the protocol of new panel correctly, at least, it must be able to receive the character string. Now, the trouble is that IPC can't receive characters from new panel.

CPallini 25-May-17 3:52am

Well, you have the opportunity to debug the code at very low level, so you can actually see if nothing arrives from the serial line. In such a case, follow Griff's suggestion and check all the serial port settings.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2017-05-24T20:03:00

RS232 is a funny beast at times - it's not just the baud rate that is configurable, it's also the bits per character, parity, stop bits, and control lines.
Start by checking with Hyperterminal (or similar) that the computer receives similar (or better identical) data from both panels when you use them without changing any communications parameters - if you do, then the basic communications are fine, and your software shouldn't need any parameter changes. Then start looking at control lines (and 232 has several output lines from your computer end which can be used to prevent the remote device transmitting, so check RTS/CTS, DTR/DSR/DCD for starters and make sure that they are the same when you compare your software to the terminal program.
When you have data transfer, you can start looking at the data content that your software receives - and bear in mind that if the panels come from different manufacturers they may not use the same protocol so the packets may be wildly different.
I'd change the software to log raw inputs to a file, and run the old and new panels through the same range of tests, then examine the data using a hex editor to find out what they are sending.

Sorry - but we can't just tell you "do this" because there are far, far too many variables in play here! You will have to do some research and experimentation to find out what is going on before you can start coding for any differences.