MODBUS Craziness

W

Thread Starter

Wes

I have a Motorola MOSCAD system that is monitored with In Touch WonderWare software. There are two computers, GMC 1 and GMC 2, that are identical. GMC 2 works, GMC 1 does not. GMC 1 is not talking to the MOSCAD RTU. I can swap cables and the problem stays with GMC 1. This tells me the cable and RTU are good and the problem is with GMC 1. Both computers have a piece of hardware called a "Rocketport" that provides multiple serial ports. Port 7 is the port programmed to connect to the MOSCAD RTU. I tried to change ports with no success. The Rocketport has been reseated.

Anybody have any ideas on how to troubleshoot from here? Any thoughts on how to change ports? I have done more during troubleshooting than what is written here, but did not want to make the post too long.

Anybody out there willing to help me with this problem? I have hit a brick wall. Any help will be appreciated.

Wes
 
W

You can try to swap the "Rocketports." Generally for problems like this I look for any recent changes to the computer that is not working and make sure that the computer is sending and receiving with the com lights or a breakout box. I would also make sure that the program on the computer that is doing the Modbus interface is actually running. If that does not provide any relief, I would suggest that you look at the actual modbus traffic to see if you can get a clue. There are comm programs that will allow you to look what is being sent and received. There are free ones and ones that cost but some of them will let you try them out for free for a 30 days (depending on your configuration, you may also need some cabling and maybe an interface device). If you have much Modbus, it is handy to have one of these programs in your pocket and they are generally inexpensive. Google "modbus simulator."

Bill

William (Bill) L. Mostia, Jr. PE
Fellow
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.
 
C

Curt Wuollet

Look in the Rocketport manual for how to do a loopback test, this will tell you if the drivers and board are working properly. If not reload drivers.

Regards
cww
 
I performed a loopback test on port 7, it failed. I then performed a loopback test on port 8, it passed. Would really like to try and move everything over to port 8, but can not find where to configure it. Under MODBUS port configuration the speed needed, 38,400, is greyed out. Wondering if port configuration is in the Wonderware InTouch I/O Server software. If it is, I can not find it.

w
 
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