Get Mitsubishi Electric MELSEC data to MQTT and the cloud.
If your MELSEC iQ-F can serve Modbus, an AppBlocks gateway polls its registers, scales the values, and publishes them to any MQTT broker, an HTTP API, Azure IoT, or AppBlocks Cloud. The gateway is a separate device next to the controller, and its logic is a flowchart your whole team can read.
One mapping on the PLC, then the gateway does the rest.
A one-time Modbus mapping
You decide which values the PLC exposes as Modbus registers. Everything else in the program stays as it is.
Read-only unless you say so
The gateway only reads. If you choose to send setpoints back, limits are checked in the flow before anything reaches the PLC.
Secure on the way out
MQTT over TLS with QoS 0, 1, or 2, and HTTPS for API calls, so plant-side Modbus never leaves the plant.
Two steps from register map to broker.
The flow uses real block names. Open the Designer and you’ll find each one in the palette.
Step 1: Serve Modbus from the Mitsubishi controller
MELSEC iQ-F (FX5) CPUs support Modbus communication, as Modbus/TCP on the built-in Ethernet port and as Modbus RTU on a serial port. In GX Works3 you set up the Modbus device assignment, so each register the gateway reads lines up with the device memory you want to expose.
Larger MELSEC series typically add Modbus with an Ethernet or serial communication module. Older CPUs without either can use a Modbus protocol converter.
- Modbus/TCP on the built-in Ethernet port, or RTU over RS-485
- Expose only the device memory you choose
- The PLC program stays in charge; the gateway reads
PLC device Modbus address Gateway variable D100 (tank level) 40001 tank_level D101 (pump state) 40002 pump_running D102 (line speed) 40003 line_speed
Step 2: Poll the registers and publish
A timer sends a Modbus Request. When the PLC answers, On Modbus Response scales the value and publishes it. If the PLC stops answering, On Modbus Timeout publishes a status topic, so your dashboard can tell zero from offline.
- Function codes 01–06, 15, and 16
- Fast tags every second, slow ones every minute
- Report by exception to save cellular data
Build your first gateway in an afternoon.
Mitsubishi Electric MELSEC and the other product names on this page are trademarks of their owners. AppBlocks is not affiliated with or endorsed by them.
Questions, answered.
Do older Mitsubishi PLCs work?
If the CPU or a communication module supports Modbus RTU or Modbus/TCP, yes. Otherwise a Modbus protocol converter bridges the gap. Check your model’s manual for the details.
Can I use a serial port instead of Ethernet?
Yes. Modbus RTU over RS-485 works with the RS-485 module on a Tibbo gateway, and one bus can carry several slaves.
Is Modbus TCP secure?
Modbus has no authentication or encryption of its own, so keep the PLC-to-gateway link on the plant network. The gateway then publishes outward over MQTT with TLS or over HTTPS.
What hardware do I use for the gateway?
A Tibbo Project System device with an Ethernet port and an RS-485 module is the usual choice, in a DIN-rail enclosure. Add a 4G LTE module for sites without a network. AppBlocks also runs on Zephyr boards such as the ESP32. Supported boards.
Ready to connect your first device?
Start free in your browser, follow the tutorials, or book a free one-on-one session. No board yet? We’ll demonstrate everything on ours.