Q06UDVCPU MODBUS TCP

[schulzkj]

Hi, I'm having issues getting Modbus TCP communication with my Q06UDVCPU built in ethernet port and a windows based unit being used as a slave.

I'm able to use the tester from schneider to run my laptop as a master and get communication with the slave.

I'm also able to use the pyModSlave on my laptop and use my laptop as a slave with the PLC as the master. 

However, I can't get it to work with the PLC as master and the unit as the slave.

I have a connection, and am using Predefined Protocol Function 

I open the connection, confirm I have a connection, but when I run the SP.ECPRTCL, I don't get modbus communication between the two.

I have a device set for Predefined Protocol Operation Status, and see:

+0      3H

+1      3006H

+2      1005H

+3-16  FFFFH

As I mentioned, I assume I have all my parameters and control data set correctly, as I'm able to use the testers on my laptop to operate them both as I intend to use them, but when I connect them to one another, this is all I get.

I don't have a ton of info on the unit I'm using as a slave, as it's an outside supplier.  They sent us the registers and and bit data we need to accomplish our goal, which I confirmed with the schneider tester, but I have little other information on its programming.

Any help is appreciated!

[Gambit]

What error are you getting and why not use wireshark. to check te messages

[schulzkj]

I'm not getting an error.  In the operation status register, it's telling me that it's waiting for data to be received, and data not matched.  I don't have any issues like that when I use the SE tester with the slave unit, or if I use the pyModSlave tester with the PLC CPU.

I don't know anything about the wireshark, so I'm currently looking into that.

[Gambit]

Hmm looks like you got a reply though.

never got this message. But i think the identifier in the reply message is different. (wireshark should be a good way to check it recognizes the modbus  protocol )

[schulzkj]

Here's a wireshark capture of when I run SP.SOCOPEN  192.168.3.39 is PLC, 192.168.3.205 is the slave

[Gambit]

Ok But this is juts the opening of the socket(port) . this is working right ?

you have a connection to the slave.

In order to capture the traffic with wireshark you will need to mirror one of the used ports of your switch ?