Using labview to read from flow computer using modbus

[frustrated44]

I am doing a project for my final term in instrumentation and attempting to create an HMI in LabView to interface with a Floboss 103 flow computer through modbus.  All I need to do is display temp static and pressure like a meter run. 

I am using the com1 port RS 485 and converting to RS 232 to the computers Comm1 Serial port.  I have the modbus libraries and have attempted to communicate with several examples to no success.  I have set up the modbus I/O server and made my shared variables in ranges of 400100-400103 for the first parameter.  When i have the block in the block diagram from dragging it over from the project manager and run it it gives me error that the response in unreadble. 

Registers in RocLink are configured to 100-103, 200-203, 300-303, with a conversion code of 71 to make it a floating point.

Any ideas on what could be wrong or an example of how to get a value to display on the screen would be much appreciated

Also I am using Labview 2009

[Robbob]

Frustrated,

A few questions for ya:

1) You mention modbus library but also a modbus I/O server. Which one are you using?

2) What type of serial cable are you using - null modem or straight through?

3) Can you open hyperterminal and do a loopback test to verify the serial port is working?

4) Are there any coils you can read from the device instead? These are a little easier to read and we don't have to worry about conversion codes

5) Are you getting any sort of error codes?

6) Do you have an extra computer that you can run the serial modbus slave and serial modbus master examples on?

7) Have you tried using any other software to communicate to verify everything is set up correctly? Modbus poll is a useful shareware tool to make sure everything is set up correctly. If this doesn't work, then we know the problem isn't with labview, but with hardware. If it does work, something is wrong on the software side.

I have also seen issues with 485/232 converters in the past causing issues.