PLC and PC communication via SLMP Protocol

PLC and PC communication via SLMP Protocol

Overview of document

Overview of PC and PLC communication via SLMP

The purpose of this document is to provide simple solution for PC and PLC communication via SLMP. 

A the beginning, there will be presented how to set communication parameters in GX Works3 for SLMP protocol. Then it will be show how to read a registry value from PLC using Hercules SETUP utility program. In addition, presented document contains information how to create your own console application in C# language.   

Example effects

SLMP communication using Hercules SETUP utility

SLMP communication via Console Application

Details of PC and PLC communication via SLMP

Parametrization in GX Works3 

PC and PLC connection

To establish connection between PC and PLC:
Connect devices with Ethernet wire → Create new project for your PLC select → Select Online → Current Connection Destination… 



For Direct Coupled Setting we need only to put IP Address of Adapter and confirm settings (if communication test was positive).

Otherwise select Other Connection Method (Open the specify Connection Destiny window) →  CPU Module Direct Couple Setting → select Ethernet → put IP Address → Yes

Remember to set IP Address of your PC in the same subnet as the PLC

Execute Communication Test  and confirm the settings.


Module Configuration

Double click on Module Configuration from the project tree → by drag and drop place hardware components that represent the actual state.

 
You can also select Online → Read Module Configuration from PLC.



Ethernet Port

To start using SLMP Protocol set parameters as follow:



Set External Device Configuration by double click on <Detailed Settings> next to this parameter.

Add SLMP Connection Module from Ethernet Devices by drag and drop it → set TCP protocol → set Port No. on 2000 → Close with Reflecting the Setting.



After this operations select Check and Apply.

Write to PLC...

To write your project to PLC  select Online →click Write to PLC... →  select  Parameter + Program(F) → Execute


Reset PLC and go to RUN mode.

Monitor D200 parameter

Add parameter D200 twice to the Watch window by clicking on the row and putting “D200”. For the first case choose Decimal display format, and Hexadecimal for second one. To monitor and change current value click on Start Monitoring.



Hercules SETUP utility


Connection with PLC

Open Hercules SETUP utility application → select Test mode  → set Module IP: 192.168.3.250 (IP address of PLC set in GX Works3) → set Port: 2000 (as in Ethernet Configuration in GX Works3)

If you don’t have the application installed yet, here there is a link to the website with the software:  

https://www.hw-group.com/software/hercules-setup-utility




Make sure that IP address and Port No. are the same as those set in GX Works3.

After this operation you should be able to start communication. To do this, press Connect.




Connection operation status will be displayed in Received data: Connected to 192.168.3.250 (PLC address).

Sending request to  PLC

Before you will send request to PLC, make sure the settings look like these: 


 
Put the request into Send section:

“50 00 00 FF FF 03 00 0C 00 10 00 01 04 00 00 C8 00 00 A8 01 00”

Which is synonymous with: 

Request

50

00

00

FF

FF

03

00

0C

00

 

Subheader

(without serial No.)

Request destination

network No.

Request destination station No.

Request destination module I/O No.

Request destination multidrop station No.

Request data length

Response

D0

00

00

FF

FF

03

00

04

00

 

10

00

01

04

00

00

C8

00

00

A8

01

00

Monitoring timer

Comand (0401:Read)

Subcommand

Head Device No.

 (0xC8 => 200DEC)

Device code (D register)

No. of device  points

00

00

BE

DC

 

Error code

Response data

 

Select Hex option and click Send.

In presented situation, sent command asks PLC about D200 register.

All sent commands are displayed in the Sent data section.



Data from the PLC are received and displayed in hexadecimal form in Received data section.

Observing  this register in Watch window in  GX Works3 you can confirm that data was sent properly.

C# Console Application

Run ready application

Write the IP address of PLC into byAdres[] as shown below → put ipAdress and 2000 (Port No. - value as in GX Works3 settings) as arguments of ConnectTCP function

 

using System;

using System.Net.Sockets;

using System.Net;

using System.Net.NetworkInformation;

 

namespace SLMP_SampleFrame

{

    class Program

    {

        static TcpClient tcpC = new TcpClient(); // Global TcpClient object

        static void Main(string[] args)

        {

            byte[] byAdres = new byte[4];

            // set IP address of PLC

            byAdres[0] = 192; byAdres[1] = 168; byAdres[2] = 3; byAdres[3] = 250;

            IPAddress ipAdress = new IPAddress(byAdres);

            ConnectTCP(ipAdress, 2000);//connection for set IP address and Port No.

            if(tcpC.Connected) //if TcpClient is connected perform next lines

            {

                Read_D200(); // read D200 register

            }

            Console.ReadKey();

        } 

    }

}

 

Main program

In “Part of code for read D200 register” section, put the request into payload variable: 

“0x50, 0x00, 0x00, 0xff, 0xff, 0x03, 0x00, 0x0C, 0x00, 0x10, 0x00, 0x01, 0x04, 0x00, 0x00, 0xC8, 0x00, 0x00, 0xA8, 0x01, 0x00” 

Which is synonymous with: 

Request

50

00

00

FF

FF

03

00

0C

00

 

Subheader

(without serial No.)

Request destination

network No.

Request destination station No.

Request destination module I/O No.

Request destination multidrop station No.

Request data length

Response

D0

00

00

FF

FF

03

00

04

00


10

00

01

04

00

00

C8

00

00

A8

01

00

Monitoring timer

Comand (0401:Read)

Subcommand

Head Device No.

 (0xC8 => 200DEC)

Device code (D register)

No. of device  points

00

00

BE

DC

 

Error code

Response data


Each byte in created table is hexadecimal and  separated by a comma.                                                                                

In presented situation, sent command asks PLC about D200 register.

 

#region Part of code for read D200 register

        static void Read_D200()

        {

            //Request frame for read D200 register

            byte[] payload = new byte[] { 0x50, 0x00, 0x00, 0xff, 0xff, 0x03, 0x00, 0x0C, 0x00, 0x10, 0x00, 0x01, 0x04, 0x00, 0x00, 0xC8, 0x00, 0x00, 0xA8, 0x01, 0x00 };

            NetworkStream stream = tcpC.GetStream();

            stream.Write(payload, 0, payload.Length);

            byte[] data = new Byte[20];

            stream.ReadTimeout = 1000;

            try

            {

                Int32 bytes = stream.Read(data, 0, data.Length);

                if (data[9] == 0 && data[10] == 0)

                {

                    byte lowbyteResponse = data[11];

                    int hibyteResponse = data[12];

                    int afterConversion = (hibyteResponse << 8) + lowbyteResponse;

 

                    // Show information about D200 register and operation status

                    Console.WriteLine("Read D200 finished correct!");

                    Console.WriteLine("Readed value D200 (HEX): Hi byte[" + hibyteResponse.ToString("X") + "], Low byte [" + lowbyteResponse.ToString("X") + "]");

                    Console.WriteLine("Readed value D200 (DEC + Converted): " + afterConversion.ToString());

                }

                else

                {

                    Console.WriteLine("Error in Answere");

                }

            }

            catch

            {

                Console.WriteLine("Error in interpreter");

            }

        }

        #endregion

 

Part of code for read D200 register


Launch your application.



Data from the PLC are received and displayed in console. Firstly in hexadecimal form, detail Low and High byte. Secondly this bytes are converted and displayed in decimal form.

Before displaying register value, information about operation status is shown.

Observing  this register in Watch window in GX Works3 you can confirm that data was sent properly.

Caution!

Presented code is only a sample program, so it should not be run directly on a real object! Customize the created application to your needs.

The number of sent and receive data can vary. In presented example, the number of frame elements is static.

Modifications

MakePingTest

Adding this function will make establishing a connection easier. User gets information whether the device responds.  

#region Function for perform Ping test with real PLC

        static bool MakePingTest(IPAddress IPAddressForTest)

        {

            bool pingAns = false;

            Ping pingSender = new Ping();

            PingReply reply = pingSender.Send(IPAddressForTest);

            if (reply.Status == IPStatus.Success)

            {

                pingAns = true;

            }

            return pingAns;

        }

        #endregion

 
Function for perform Ping test with real PLC

SelfTest

You can also add function that will check the correctness of the sent data frame. This function compares sent and received data (in this case the test is performed on a 5-element set). If data match, then data can be exchanged between devices and communication starts

       #region Part of code used to verify whether the communication function operates normally or not

        static bool SelfTest()

        {

            bool loopTestAns = false;

 

            byte[] loopMessage = new byte[5] {0x41, 0x42, 0x43,0x44, 0x45}; // 5 elements for test - "ABCDE"

 

 

            //Request data length

            int needByteMessage = 2 + 4 + 2 + loopMessage.Length;

            byte lowByte = (byte)(needByteMessage & 0xff);

            byte highByte = (byte)(needByteMessage >> 8 & 0xff);

 

       

            byte[] payload = new byte[] { 0x50, 0x00, 0x00, 0xff, 0xff, 0x03, 0x00, lowByte, highByte, 0x10, 0x00, 0x19, 0x06,0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

 

            //number of loopack data

            lowByte = (byte)(loopMessage.Length & 0xff);

            highByte = (byte)(loopMessage.Length >> 8 & 0xff);

            payload[15] = lowByte; payload[16] = highByte;

 

            // loopack data

            for (int i = 0; i < loopMessage.Length; i++)

            {

                payload[17 + i] = loopMessage[i];

            }

 

            NetworkStream stream = tcpC.GetStream();

            stream.Write(payload, 0, payload.Length);

            byte[] data = new Byte[20];

            stream.ReadTimeout = 1000;

            try

            {

                Int32 bytes = stream.Read(data, 0, data.Length);

                if (data[9] == 0 && data[10] == 0 && data[11] == lowByte && data[12] == highByte)

                {

                    loopTestAns = true;

                    for (int i = 0; i < loopMessage.Length; i++)

                    {

                        if (loopMessage[i] != data[13 + i])

                        {

                            loopTestAns = false;

                        }

                    }

                }

            }

            catch

            {

                loopTestAns = false;

            }

            return loopTestAns;

        }

        #endregion

 
Function for check the correctness of the sent data frame

Simple library

It is possible to use simple library. All data you can find in attached file: „Simple Library for SLMP communication.zip”. Inside you can find necessary DLL file to import your project and sample program where this library was used.

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