RS485 - data trap

Posted on 2005-02-27
Medium Priority
Last Modified: 2010-08-05
Some data is retrieved on a win2000 PC using the RS485 protocol and used by a 3rd party application.  How can I trap this data and re-use it for another application without disrupting the 3rd party application ?
Question by:pascalvercammen
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Expert Comment

ID: 13416348
You would need  software that could hook into the com port prior to starting your 3rd party application.

An application that can hook into a com port in this way is Portmon from http://www.sysinternals.com however this is only used to monitor the data. You would need to modify your software to work in a similar way.
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Expert Comment

ID: 13416364
The other way that may work is to have a second RS485 port, use your software to listen in to the data without interacting.

Author Comment

ID: 13417662
Hi Snerkel,

Suppose I install a second RS485 port, how can I listen to data flowing in the 1st port.  I don't understand how you can do this.
Or is this a hardware method to split the data flowing into port 1 ?
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Accepted Solution

snerkel earned 1000 total points
ID: 13417733
Basically the RS485 cable is looped into both physical ports, the application on the second port sees the data that is being sent/received by the 3rd party software.

A way to do it on an RS232 line http://www.lammertbies.nl/comm/cable/RS-232-spy-monitor.html I use this method on a regular basis RS485 can be monitored in a similar way... how many wires are used in your project for RS485?


Author Comment

ID: 13417844
Great !
At this moment I don't know yet how many wires are being used because the app I'm talking about is installed at our customer and I have not seen it yet.  But I needed a possible solution before I go on site.
At least now I know it's possible.

Many thanks.

Expert Comment

ID: 13417855
Personally, I would install a second RS485 port and so long as it doesn't exceed the maximum number of allowed devices you can listen in on everything.  Is it 2 pair or 1 pair?  RS485 backbone?  Either way... you need software that'll read your RS485 port.


Author Comment

ID: 13417876
OK, thanks for the advice

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