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This lesson is part of the OPC-UA and Devices in Ignition course. You can browse the rest of the lessons below.
2:54Connecting to Modbus Device
4:21About Modbus Address Mapping
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Modbus Over Serial Device Connection
Learn how to connect to a device via Modbus over serial, using the Serial Support Gateway module and a Modbus RTU device connection.
Video recorded using: Ignition 8.1
Transcript(open in window)
[00:00] Ignition is able to communicate with Modbus PLC devices over a serial link using the Modbus RTU protocol. To be able to establish disconnection, you must first have both the Modbus driver module, as well as the serial support gateway module. Once those two modules are installed, you will be able to create the Modbus RTU over a serial device connection. Let's take a quick look at how to create the device itself. To do that from the configure page, I will head to the device connection section under OPCUA here on the left. From there, you can see I have no devices created. So let's press the create new device button to launch the device creation wizard. Here, we see a list of all the communication drivers available in my gateway. We are interested in the Modbus RTU driver. As you can see from the description, it will allow for our RTU over serial connection. I will head to the bottom and click next. I will name the device serial one and give it a description. Under connectivity settings, we see our serial port setting, which allows us to select our communication port. In my case, my device is on serial port comm three. So I will type that on here. I also need to configure my bit rate to be 9,600. Everything else looks correctly configured for my application. So I will move on to a few settings I want to highlight under advanced properties. Most of these properties can be left alone. But one important property to point out would be the zero-based addressing. The driver defaults to one base. Meaning that the address range will start at one. However, you can toggle this property to start the address range at zero if needed. The device I'm trying to connect to is one base. So I can leave this setting alone. The next property down, span gaps, optimizes requests by grouping them into large chunks. But if a bad address is present in that range, then every other address in that request will also be flagged with bad quality. This leads to a larger amount of bad quality tags that appear in the tag browser. In this scenario, toggling span gaps can aid in finding those bad addresses as only the badly addressed tags will be flagged as bad quality. I am done with my devices configuration, so I'm going to click the create new device button. That's it. We have created our device connection. Now that we're connected, we can start creating tags manually or with Ignition's address mapping feature. We'll see examples of both methods in upcoming videos.