Read Modbus Input Registers

[mcook2112]

Hi All,

Apologies if this has been covered before, but this is my first post and I am fairly new to the Labview environment. I am also fairly new to Modbus communication. I am trying to extract the temperature readout from a flowmeter via a Modbus to serial connection. The hardware and connection side is now all OK, and I am able to communicate with the device using QModMaster as per the screenshot below with start address and number of registers identified. I am now trying to duplicate this connection in Labview using the Plasmionique Modbus Master add in. My COM port settings would all appear OK (57600 baud rate, 8 data bits, 1 stop bit, even parity). Any help in getting this communication down would be much appreciated. I am getting an error code about invalid communication as per below. This forum has been a great help to date. 

Thanks,

Marcus

 

 

 

[LucianM · Accepted solution]

I don't have the modbus library to check exactly but it seems you are reading register 4500 decimal with LabVIEW and register 0x4501 with the other app. Could it be that you are trying to read an invalid register?

You can set the radix of numeric constants by right-clicking on the constant and choosing Visible Items -> Radix.

[mcook2112]

Hi Lucian,

Thanks for your help, its enabled me to solve the issue. You were correct in that I had to right click on the constant and change the radix to hex. I actually ended up using the Plasmionique Modbus Master Comms Tester example as it has a more friendly GUI, now I will work back to simplify this down for my application. 

 

 

The conversion to temperature was fairly straightforward from the input register.