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Old April 1st, 2005, 07:35 AM   #1
mordred
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Omron CPM2a communication serial vs USB

I have 5 packaging/label lines that use the Omron CPM2A processor that is interfacing with the following. Noax touchscreen, GSE 650 scale head, datalogix 2400 scanner and two strapmasters. The PLC is used primarily to handle these devices including the conveyers, a couple of photoeyes and passes communications to the touchscreen which is also connected to a database server.
The main problem I have been experiencing is due to our high rate of boxes per minute. We encounter communication drop outs and the processes will intermittantly hang or take longer at various points. This in turn causes the CPU to semmingly lose track of certain sequences of events. I know the system was originally designed to utilyze USB connections however at that time USB had too great of a tendency to change its Comm ports.

Does anyone know of either a USB to RS 232 adaptor or a means of fixing the comm ports?
Would the USB offer me a greater rate of communication from the PLC to touchscreen than offered by a standard RS 232 connection?
Also the PLC is written event driven. Would changing the source code to interupt driven offer any advantages?
I would post the source code however not being my program I am unwilling to infringe on copy writes.

Any help in either diagnostics or suggestions would be appreciated.
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Old April 1st, 2005, 03:12 PM   #2
mordred
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I guess no one has any suggestions?
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Old April 1st, 2005, 03:50 PM   #3
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Have you considered using serial analyzer to determine where the comm dropouts originate? IMHO that would probably tell you the next step to take.

USB adapted to serial would still limit you to a serial baud rate.
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Old April 1st, 2005, 04:04 PM   #4
ArikBY
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I would try to change the communication speed to 19200 or higher.

Omron originaly come with 9600-7-E-2 But the port is flexible.
I dont know your HMI but in most of them the speed can be change.
USB adapter would not help as Ron mentioned.
If you need help how to change the speed let me know
I will direct you.
All the best
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Old April 5th, 2005, 07:15 AM   #5
mordred
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they have already tried various speed changes. I will look into a serial communications test probably have to hire someone to test it as we don't have that particular tester. The research we've done so far is showing the dropouts occurring between the server database and the touchscreen.

Last edited by mordred; April 5th, 2005 at 07:18 AM.
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