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We are actually using Schneider electric OTB1SODM9LP and TM2AMI2HT remote IO modules for our applications.

We wanted to read the digital input status connected to the OTB1SODM9LP module through modbus RTU. For that We framed modbus commands and sent it to the module. After we send the command, we could not get the reponse back from the module.
We used "30" as our module address. With that we framed a command like below.

1E 03 00 00 00 01 C6 64..

How do we get the response from OTB1SODM9LP module. we checked the data through serial port, it is showing only the command data, but not response data.

Please let us know whether the read command framed to read the holding register value is correct ? or do we need to change the data frame or any other settings.

Similarly the TM2AMI2HT analog input module also not sending us the response.

Note: we have data sheets and other info which we got the website. but nothing helped us.

The crc appears incorrect. Try this...
1E 03 00 00 00 01 86 65

Hello,

Try use Modbus tester from www.modbus.pl

Using the tester you can see the all frames send/receive over Modbus RTU.

Regards,
Andrzej

I see you put your address in hex. perhaps when you set it it was actually 30 hex. You can also check the status of the transmission to see if you are communicating, if there are any. Many times, it is just a loose wire. We usually measure the DC bias voltage across the terminals to verify you are communicating.

If all else fails, you can try our modules and we offer free tech support.

http://daq.icpdas-usa.com/m_7000_remote_data_acquisition_modules_vi a_modbus_protocol.html