Roboflow + Modbus TCP
Read and write coils and registers on any Modbus TCP device, so a detection can reject a part, signal a robot or count output.
How to connect Modbus TCP to Roboflow
6 stepsSet up an edge device
Register a device in Deployment Manager and connect it to the same network as the Modbus device, with port 502 reachable. The device runs your Workflows on site.
Get the device's register map
From the device's manual or PLC program, note the coils and registers you need, its unit ID and, for 32-bit values, whether it uses big or little word order.
Add the PLC Relay
On the device's Configuration tab, add the PLC Relay service, choose Modbus TCP and enter the device's IP address (with :port if it is not 502), its unit ID (0 to 255) and the word order.
Define your tags
Add each value by area and address: coil:0 for a BOOL, holding:100 for an INT, DINT or REAL. Discrete inputs and input registers are read-only. Simulation mode lets you test without hardware.
Add PLC blocks to the Workflow
Add a PLC Reader to bring values in and one PLC Writer for each value you send out, pointed at the relay. To skip the relay, set Connection mode to Direct (Modbus TCP) and enter the device's IP address, port and unit ID.
Deploy and monitor
Deploy the Workflow to a stream on the device. The device page shows the relay's connection state and live values, and a PLC Disconnected alert tells you if the link drops.
What teams build with Modbus TCP
Reject a defective part
Set a coil when the Workflow finds a defect, and let the PLC fire the reject mechanism at the right moment.
Signal a robot
Write a part's class or position to holding registers that the robot program reads before it picks.
Count output per shift
Write running counts of good and rejected parts to holding registers the PLC and HMI already display.
Works with
| Product | How Roboflow connects |
|---|---|
| Schneider Electric Modicon | Direct or PLC Relay |
| ABB AC500 | Direct or PLC Relay |
| Mitsubishi MELSEC iQ-F | Direct or PLC Relay |
| Beckhoff TwinCAT | Direct or PLC Relay, with TF6250 |
| Universal Robots | Direct or PLC Relay |
Questions
Any device that acts as a Modbus TCP server, including PLCs, robot controllers, drives and remote I/O. Roboflow connects as the client and reads or writes the addresses you configure.
No. The PLC blocks can connect straight to the device in Direct (Modbus TCP) mode. PLC Relay keeps the address and tag list on the edge device, so the same Workflow runs on every line, and adds live monitoring and a disconnect alert.
The device stores 32-bit values in the other word order. Switch the relay's word order between big and little and read the value again.
No. The PLC blocks run on your own device on the plant network, close to the camera and the equipment, not on Roboflow's hosted API.
The PLC blocks and PLC Relay are part of the Enterprise plan. Talk to our team to add them to your workspace.
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