Modbus TCP: Setup TCP communication step by step and use the data in the PLC
Disclaimer and Topology
The goal is to set up the Modbus TCP app from scratch and communicate with a device. Here we have an example with Wago 750-881 buscoupler equipped with 2 digital Inputs, 2 digital Outputs and 2 analog Outputs. Additionally the communication with a XM22 device will be shown.
Modbus TCP connection
IP addresses
XM22: 192.168.1.25
ctrlX CORE: 192.168.1.1
WAGO buskoppler: 192.168.1.15
Requirements
ctrlX CORE - x3 or x7 or a ctrlX OS installation
Modbus TCP app installed>=1.20 + license
Some Slave/Server device
1 - Setup the communication
With Wago
Open the app page and click on "Add Modbus TCP Device".
Add device In the window we have to insert the Modbus TCP device infos and click over save:
A name of choice
The device IP address
The device port
The unit ID: Normally 255 (Remark to the unit ID, it depends on the device, normally default is 255. On Modbus TCP it has to match with the connected hardware, but can be present multiple times. In Modbus RTU it's the unique slave address)
Device Parameters
Click on "add subscription" button.
Add subscription
The subscription should be fulfilled with the right parameters:
Name chosen
Function Code: the function that the subscription should fulfill, it depends by what we need to do and can be found in the device description/datasheet:
FC1: Read Multiple Coils
FC3: Read Multiple Holding Registers
FC4: Read Multiple Input Registers
FC6: Write Single Holding Registers
FC15: Write Multiple Coils
FC16: Write Multiple Holding Registers
FC23: Read/Write multiple Holding Registers
The address that we want to read/write
Sometimes (if needed) the datatype contained by the register
The number of the addresses that we want to use
The Polling interval
Setup Subscription
Once I have added all the subscriptions the overall setup looks like this:
Modbus Wago
All the data are then present in the datalayer for editing and reading and can be used by any app.
Modbus TCP Datalayer
with XM22 device
Open the app page and click on "Add Modbus TCP Device" and add the device data.
TCP server and settingsWe have shared the following data: an array of 100 uint so they will be 200 bytes. Any register from ctrlX side is then an uint16 variable. Additionally we have 8 coils.
Data shared
We add the right configurations, since we want to keep updated all the 100 variables the register configuration will look like this:
Registers configuration
The overall configuration will be the following:
Global Configuration2 - Import the data inside PLC Engineering
Login on time in the PLC with an empty project (or with your project) and then logout. Right click on the datalayer, select real time data and then selectively from ctrlX CORE.
Import Data Modbus Datalayer
To select the modbustcp_client entry, click on the import button and after this all the data will be in the Datalayer_Realtime tree.
ModbusTCP PLC app ImportNow we can use the Modbus TCP data inside the PLC App
