Communication issues with MODNET driver

[nicolas.goubin]

Dear all,

I am struggling with communication issues on CITECT STUDIO 2018 R2. I need to use citect generic MODBUS TCP/IP driver : MODNET since I want to read data from a non-schneider device (usually i would use MODNET30 for M340 and M580 devices, which is working fine).

I set up MODNET configuration using the I/O setup wizard with the correct IP adress and port (502) and i setup the address of my variable of type LONG as '402055'. I get no compilation errors, yet i keep having #BAD value on my runtime.

I tried using a Modbus poll tool to talk to my slave device and it is communicating correctly.

I quickly checked the citect.ini file, i see that there are no parameters or section 'Modnet' written in it. May that be the cause of the problem ?

(See attached screenshots...)

Sincerely yours,

Nicolas.

[olivier_vallee]

Hi @nicolas.goubin,

What is the slave address of your "non-schneider device"? Typically if it is just a stand alone Modbus on TCP, it would have slave address 1. But in your screen shot you gave it number 26?

What Modbus Test Client tool did you use? Can you attach a screen shot of successful comms with this device and the tool?

Does your device have all the Modbus address ranges? E.g. 0x 1x 3x 4x address spaces?

Since the MODNET will attempt to read address 400001 on startup before bringing the unit online.

You shouldn't need to modify the MODNET parameters to get it working, unless there is something unique about your device, that requires customization of the driver. It might also be helpful to enable driver logging to see what message is being returned, any error code or how far into the driver initialization it gets.

[MODNET]

Debug=1

DebugStr = <port name> ALL

[nicolas.goubin]

Hi,

Thank you for your reply.

I thought the port number '26' was to identify each port on the API card in the SCADA system. Thus, i usually increment it by 1 every time i add a new I/O device. I just tried to put 1 as number port instead of 26, same issue occuring...

I used 'Generic Modbus/JBus Tester' from 'Square D Company' to call my device (See the screenshot  attached to this post). You can see a successful test with 400001 address targeted.

[olivier_vallee · Accepted solution]

Hi @nicolas.goubin,

I just ran up a simulator (ModSim32) and Plant SCADA, with similar settings, and I was able to communicate successfully with it. So from your screen shots, I can't see where the error in your config is.

The two approaches which I think will bear most fruit would be:

1. Create a new test project with just this one device and one tag, see if it can communicate

2. If not able to communicate, enable driver debugging and look in the log file for hints on what is failing

The only other thing that could be causing issues is if the Modbus device has a special address structure (gaps in address range) and Plant SCADA is trying to access (via block read request) non-existent address space.