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In one of our previous projects, we wrote about how to connect Modbus RTU slave devices to WolkAbout IoT Platform by using WolkGateway and WolkGatewayModule-Modbus.
This time, the focus is on a Modbus TCP/IP slave (server) device that communicates with WolkGatewayModule-Modbus acting as a master (client) using Ethernet as its physical layer. The parameters of the connection, the slave’s IP address and port, are configurable through a.json file.
Finally, the data from the slave’s registers are exchanged with WolkGateway through WolkGatewayModule-Modbus and then with WolkAbout IoT Platform.
The Modbus TCP/IP slave used in this project is actually a simulation of an offset printing machine described in the related Hackster project. A list of Modbus registers present on the slave is defined in a .json file. Finally, a visualisation dashboard is created on the Platform, providing insight and control over the simulated offset printing machine.
Here is an overview of the architecture of this project.
Connecting multiple Modbus TCP/IP slaves (servers) is possible by deploying additional WolkGatewayModule-Modbus and editing their register mapping and connectivity details files.
This project can be easily modified to work with a different Modbus TCP/IP slave instead.
Hardware SetupMake a hardware connection following the diagram below. Do note that both the hardware connection of the offset printing machine simulator and WolkGateway device which can run on a generic Linux device (specifically Raspberry Pi Model B+ is used in this demo) are presented here.
WolkGateway bridges communication between WolkAbout IoT Platform and multiple non-IP-enabled devices connected to it through modules. The modules enable communication with subordinate devices by implementing the device’s network communication protocol on one end (Modbus TCP/IP in this project) and parse data between the Local Mosquitto MQTT broker on the other end.
Start with connecting to the Raspberry Pi and cloning the WolkGateway repository:
git clone --recurse-submodules https://github.com/Wolkabout/WolkGateway.gitAfter that, install WolkGateway’s dependencies by running:
sudo apt-get install mosquitto cmake python python-pip && sudo python -m pip install conanNow that the dependencies are installed change directory into WolkGateway and run the configure.sh script. This script prepares the build system and compiles OpenSSL. This step takes some time (up to 10 minutes), so while waiting for this step to finish, create a gateway on WolkAbout IoT Platform.
Head over to demo.wolkabout.com and register/log in with your account. Next, switch to the Device Management tool from the application menu.
Press + and from the dropdown menu select Create device without device type.
Enter the name for the gateway and the optionally a device key.
Set the Protocol to WolkAbout MQTT Gateway, Connectivity Type to MQTT and Sub device Management to GATEWAY.
Tick the checkbox for Create Default Semantic and click Save.
A pop-up will appear with the gateway name and the key, as well as its password.A pop-up appears with the gateway name and the key, as well as its password. Save this information by using one of the options from the bottom on the left as you need to enter them into WolkGateway/out/gatewayConfiguration.json.
After the configure.sh script finishes, change directory to WolkGateway/out/ and run make. To run the application correctly, you need to enter the device credentials into gatewayConfiguration.json:
{
"name": "",
"key": "",
"password": "",
...Before running the gateway application, make sure that Mosquitto is running by invoking
systemctl start mosquittoThen start the application with
./WolkGatewayApp gatewayConfiguration.jsonAfter a couple of seconds, the gateway connects to the Platform and performs its initial configuration. Now, it is possible to register devices through the gateway.
For easier use, create a service that runs the gateway by creating a new file wolk_gateway.service and copy the content from the project’s attachments. Make changes to the username and the path if necessary. Then move it and enable it with the following commands:
sudo mv wolk_gateway.service /lib/systemd/system/wolk_gateway.service
sudo chmod 644 /lib/systemd/system/wolk_gateway.service
sudo systemctl daemon-reload
sudo systemctl enable wolk_gateway.service
sudo systemctl start wolk_gateway.serviceTo check the state of the service use
sudo systemctl status wolk_gateway.service, and also use restart, stop and disable commands if needed.
All of this completes the setup for WolkGateway repository, resulting in a service that routes the data from the Modbus module to WolkAbout IoT Platform.
Then change the directory to WolkGatewayModule-Modbus and run the configure.sh script. This time the configure.sh script takes considerably less time to finish as OpenSSL is already compiled and cached. Next, change the directory to WolkGatewayModule-Modbus/out/ and run make.
Now that you have built the project, the next step is to edit the configuration files needed to run this module correctly: devicesConfiguration.json and moduleConfiguration.json
moduleConfiguration.json holds information related to Modbus connectivity, while devicesConfiguration.json contains the details of Modbus registers and how to interpret them.
After configuring these files and running the WolkGateway application, you can start the Modbus module with:
./modbusModule modbusConfiguration.json devicesConfiguration.jsonStarting the Modbus module tries to poll the registers of the slave devices and sends a device registration request based on devicesConfiguration.json through WolkGateway to WolkAbout IoT Platform.
By following the same steps as for wolk_gateway.service, create a service for the Modbus module using the modbus_module.service file from the project’s attachments.
Now that the Modbus module has been registered on the Platform and the register data is being sent to the Platform, you need a way to display it and send new values and have them written into the Modbus registers of your slave devices. To achieve this, first, create a Dashboard.
Then start adding widgets that fit your slave device: Actuator widgets for coils and holding registers (read/write) and Reading widgets for input contacts and input registers (read-only).
ConclusionNote: There may be slight differences between the production version of WolkAbout IoT Platform and the Tutorial
By connecting a Modbus TCP/IP slave (server) to WolkAbout IoT Platform, you can have an in-depth insight into the overall operation, including alarm notifications, productivity, as well as control over your device. Most importantly, you can do all of this remotely instead of on-premise, which has been the case so far.
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Do you have an IoT project in mind? Share it with the WolkAbout Community through Hackster.io. We'd love to see what you can do using WolkAbout IoT Platform!
If you need help developing it, we've got you covered! Read our team’s projects and stay tuned for the new ones.
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