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Sanchez

Modbus RTU Slave

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Hello,

I have created a serial device with protocol Modbus RTU Slave. I also created some channels and asigned the respective modbus addresses. I can monitor the activity in the port but there is no response from DAQfactory, I see only RXs. I am not sure how to configure the channel table (see attached). Where do I specify the modbus address (i.e 40001) in Ch# or Mod Slave#? What effect does the I/O Type parameter has? I can not change it.

Thanks

post-915-1226694525_thumb.jpg

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You should never create channels with a device type attached to the Modbus Slave protocol. Slave means that some other device does the querying and DAQFactory responds. So, creating channels is rather moot. What you need to do is tell DAQFactory what to do when a query comes in from the external Modbus Master. The query is going to have a tag number on it. This is what goes in Mod Slave #, but it should go into the Mod Slave # column for an existing channel that is getting data from somewhere else, probably a local device.

Please review the help for using Modbus Slave. There are some specifics on what tag #'s you should use. Note that DAQFactory uses 0 indexed addressing, so tag #1 in DAQFactory is 40,002 for some modbus masters. Note also that tag #0 is not supported (indicates not used) and so 40,001, and 30,001 are also not supported.

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