The ReadInputRegisters doesn't work

[Anonymous]

Hello everybody,

I use a Modicon M221 TCP with EasyModbusTCP library on M.VisualStudio 2015. I have no problem with the connection which works properly.
However when I try to recover some data from my TCP with ReadInputRegisters it send me back only one value which is weird... I actually connect with the TCP simulator with is IP adress (127.0.0.1) and when i switch the inputs in the simulator it doesn't seems to impact on the values...

Here's part of my code, did I do something wrong? Thanks for your help.

Private Sub Button1_Click() Handles Button1.Click
        'This subroutine will communicate using the EasyModbusTCP to the PLC
        Dim ComError = 0 'Set communication error flag to 0
        'Specify the IP Address and Port Number that we are connecting
        Dim ModbusClient As EasyModbus.ModbusClient = New EasyModbus.ModbusClient(TextBox1.Text, 502)   'The IP of the simulator is in the txtBox
        Try
            ModbusClient.Connect() 'Connect to the PLC
        Catch ex As Exception 'What to do when an error occurs
            Label10.ForeColor = Color.Red
            Label10.Text = "Communication Error!"
            ComError = 1 'Set communication error flag to 1
        End Try
        If ComError = 0 Then 'Do the following when communication is OK
            Label10.ForeColor = Color.Black
            Label10.Text = "Logging..."
            Dim Registers As Integer() 'Where to store the information
            Registers = ModbusClient.ReadInputRegisters(0, 3) 'Read three registers starting at the first one
            Label1.Text = Registers(0)     ''''''''''''''''''''''
            Label2.Text = Registers(1)     ''Display the values'' 
            Label3.Text = Registers(2)     ''''''''''''''''''''''
            ModbusClient.Disconnect() 'Disconnect from the PLC

[Rossmann Engineering]

Hello,

I just tried and it worked. I tried with a PLC, as well as Server Simulator. Try to get the new version, otherwise could you trace communication with Wireshark, or with the Client Demo in the Download area, and send it to me.

[Jack]

Many thanks for your answer ! =)

Did you try with my code and with the Somachine BASIC software PLC's simulator ? Is there a specific kind of PLC needed for the library to work ?

I tried with the ClientDemo to connect to the simulator of Somachine Basic, and an error occured (see attached screeshot). I got excatly the same error with the PLC (Modicon TM221CE16R).
However I have not such an error with my code in M.VisualStudio, it just don't work because I can't retrieve the values of my simulator Inputs.

Thanks again for your help.

[Jack]

Just to be clear why I say my values are weird.
Here is my code :

Private Sub Button1_Click() Handles Button1.Click
        'This subroutine will communicate using the EasyModbusTCP to the PLC
        'This will execute when the user clicks the button or at specific intervals from the Timer1

        Dim ComError = 0 'Set communication error flag to 0
        'Specify the IP Address and Port Number that we are connecting
        Dim ModbusClient As EasyModbus.ModbusClient = New EasyModbus.ModbusClient(TextBox1.Text, 502)
        Try
            ModbusClient.Connect() 'Connect to the PLC
        Catch ex As Exception 'What to do when an error occurs
            Label10.ForeColor = Color.Red
            Label10.Text = "Communication Error!"
            ComError = 1 'Set communication error flag to 1
        End Try
        If ComError = 0 Then 'Do the following when communication is OK
            Label10.ForeColor = Color.Black
            Label10.Text = "Logging..."
            Dim Registers As Integer() 'Where to store the information
            Dim Registers2 As Integer()
            Registers = ModbusClient.ReadHoldingRegisters(0, 3)  **'HERE I RECOVER THE HOLDING REGISTERS**
            Registers2 = ModbusClient.ReadInputRegisters(0, 3)   **'HERE I RECOVER THE INPUT REGISTERS**
            Label1.Text = Registers(0) 'Value of 1st Register
            Label2.Text = Registers(1) 'Value of 2nd Register
            Label3.Text = Registers(2) 'Value of 3rd Register
            Label12.Text = Registers2(0) 'Value of 1st Register
            Label13.Text = Registers2(1) 'Value of 2nd Register
            Label14.Text = Registers2(2) 'Value of 3rd Register
            ModbusClient.Disconnect() 'Disconnect from the PLC

You can see in the attached sreenshot that in my form, no matter if it's the holding or input registers, the values are the same (if it's the same starting adress, here 0).
However i have changed my analog input values in the simulator...

[Jack]

Sorry for the multiple posts but I give you the WiresShark report which contained several "value refreshs". I'm not really familiar with this software so I don't really know how to use this report.

Thanks for all the help :)

[Rossmann Engineering]

Hello,

I have a Schneider LMC201C running with SoMachine Motion.
There are no requirements to use a specific PLC. If the PLC supports Modbus-TCP Server, it has to work.

I don't know which version of SoMachine Basic you use, but if you send it to me (Then send an private Message) i'll try. Otherwise we could try to have a look via TeamViewer, if you want to.

What you see for sure in your first post is, that the Client sends a valid request to the server, but the server answers with an error code, that say's that the starting address or the number of values are invalid.

Try to read values from address "2", until the server answers with a valid response. Could be that you somehow limited the amount of Registers in the PLC.

[Jack]

Hello,

Thanks for your answer.

I can't say why but the Client Demo is working today (see ScreenShot) only with the IP of the Simulator with the PLC I got the same error of starting adress, but the values of input registers stay at 0 even if I change my analog inputs on the simulator.
However I can't get the same values of 0 in VB, even with the same starting adress and number of values requested.

EDIT : Now I have the same values in Client Demo and my VB application, but still don't respond to my changes in the simulator. Moreover when I change the number of values requested (without changing the address), it modifies the values and add somme null values. (see the attachement with Client Demo and my VB form with differents numbers of values requested).

I use Somachine BASIC 1.4. I sent you my work in private message.

We could have a look on teamViewer it could be usefull.

Thanks again for your help.

[Rossmann Engineering]

Hello,

thanks for your message. I would love to help find out what is wrong there.

I would really ask you for the whole VB Project AND the SoMachine Project. So I don't have to spend so much time in creating projects out of the Code snippets.

Thanks a lot

Stefan

[Jack]

Hello, thank you for your amazing help.

I gave you a link (Private Message) to Download my all VB program, there's a part of the code that redirect the datas to a database which is not important for you it works well on my pc but won't works on yours because of the direction path, I put a condition IF(false) on it in order it doesn't execute.

I don't have any Somachine BASIC Project I just put an end on the program in order there's no error and run the simulator. In the future many different programs will run on it.

Actually that is one of my questions, do I need, and if yes, how I write in the different registers the informations I want to recover ?

[Jack]

Did you receive my private messages ? I can't see where MY private messages arrive... Where is it ?

Thanks.

[Rossmann Engineering]

Hi,

received your message. THANKS. i did not download the file so far. I will take care at the weekend.

[Jack]

Hi,

Thank you ! Another precision, my VB code works perfectly with the server simulator =)

[Jack]

Hi ! =)

Did you have a look at my work ? Any idea why the recover datas don't change with the PLC simulator ?

Thanks! =)

[Rossmann Engineering]

Hi Jack,

I tried a little bit with the SoMachine Basic Simulator, and I must say it was working perfectly.

See some screenshots attached. Maybe I did not understand the whole problem.

[Rossmann Engineering]

The Console Output

[Rossmann Engineering]

Damn small C# Programm

[Jack]

Hi,
Thank you again !

I tried exactly the same thing as you but still have some unknown values coming out (see screenshot)
My code is very similar to yours and i can't say why I don't get the values of the Memory Words back ...
**EDIT : even with your code in C# I got the same values... Furthemore, is there any reason that you used the WriteSingleRegister function ? I guess this is to test if you recover the enter values then, but that is not my case, even if I read the registers just after writing in it, I can't recover the 123 and 1234 values... **

Moreover, I think I need some explainations about registers. I thought that you didn't need to write anything in the PLC program (for the input registers) to get the values of inputs back ?

[Rossmann Engineering]

Hello,

do you use the latest dll? Otherwise we try to have a look via teamviewer. Write me pn for the connection details and when it would be possible.

Stefan

[Jack]

Hi !

I have to thank you a lot for your patience and your work, I just update the library and it's working perfectly !!! =D Both with the simulator and the real PLC.

Just one more question which i hope it'll be easy to answer to :

Why the values are the same for the inputregisters and the holdingRegisters ? I thought that the inputregisters would directly give me the values of my inputs. However I need for now, to copy the values of the analog inputs to the %MWx to get those values. It's not a real problem but just a little question ^^

Thank you again, your help was amazing .

[Rossmann Engineering]

Hello !

I also realized that, when I was working with the SoMachine Software.

normally the MODBUS-Server has four data types. Discrete Inputs, Coils, Holding Registers and Input Registers.

Coils(single bit) and holding registers (16 bit) can be transfered in both directions (Client <-> Server)

Discrete Inputs (single bit) and input registers (16 bit) can only be transfered from Server to client (Server->Client)

The mapping is different from device to device. In this case it seems that the PLC has just Bit and Word Datatypes. that means coils and discrete inputs are the same, as well as holding registers and input registers.

STEFAN

[Jack]

Hello :)

Thanks for this answer, happy to see that it's not only on my device.

I would like to thank you once again and for the last time. My project is a success and it's thank to you.

By !

[Anonymous]

[Anonymous]