garbuled communication response from modbus secondary

[vijtin]

Hello sir,

I am doing coomunication of temperature controller with Labview. In Industrial Automation OPC server i am creating modbus object with baudrate= 9600,databits= 8,parity= none & stopbit= 1 settings.

using server explorer my instrument is communicating properly & showing correct value but in Industrial Automation OPC Servers window i am getting ERROR as Garbled Communication response from Modbus secondary(10):Response too short

so can u plz tell me what is the meaning of above mentioned error ?

Vijeta

[Ryan.S]

This error means the response data size is shorter than expected, then the modbus driver think of it as a communication failure.

Try to increase the receive gap first. Option->Serial Ports, select the communication port, increase the receive gap to 40 or higher.

Message Edited by Ryan.S on 11-06-2008 01:25 AM

[vijtin]

hii Ryan,

Thanx for answer. I have already kept my receive gap as 100 (i think its maximum value) but still i am getting this error.

Poll rate is 5sec & receive timeout is 500msec (which is more sufficient for my instrument to reply).

So plz suggest me another solution.

vijeta

[Ryan.S]

There is no limit to the receive gap. You can set it to 200 or even higher, but this may reduce the polling speed.

Do you mean that you can still use Server Explorer to connect the IA OPC Server to communicate with Modbus slave device correctly with this response error?

[vijtin]

Hi ryan

ya i am using Server Explorer to connect the IA OPC Server to communicate with Modbus slave device.

so give me solution how i solve my problem?

vijeta

[Ryan.S]

Since you use the Server Explorer to connect the IA OPC Server, it uses the same Modbus driver. If the error message is always active in IA OPC Server, the data in Server Explorer should have some problem. I can only guess that occasionally the communication is not very good, but the communication is not stopped because it will retry after error.

Could you make a log file on the serial port? In IA OPC Server, Option->Serial Port, select the COM port, enable the "Diagnostic file settings", input a file name, such as c:\log.txt. Check "Value in HEX", and "Timestamp Enable". Then, the Modbus communication will be logged into the file. Upload the file and let me check the error. Maybe the error is intermittent, and doesn't affect the communication much.

[Jelly0802]

Sir, aside from the suggestions you mentioned above, do you also have other troubleshooting option for garbled communication response? I have tried all of the above options but to no avail. Also this is my first time to use the cx opc.  Please help. Thanks. 

[Prana]

Hello, I was wondering what you recommend the receive gap be set at? as of now I have mine set to 40. Do you recommend going higher? I am getting these same error messages as well. Thank you in advance for your help.