> For the complete documentation index, see [llms.txt](https://wiki.inels.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.inels.com/inels-bus/inels-design-manager-idm3/idm3-external-systems-mqtt-modbus-cloud.md). # External systems — MQTT, Modbus, Cloud *Part 3 — Reference.* *** ## 24.1 Four ways out iNELS3 can talk to things that are not iNELS. There are four routes, and they suit different jobs: | Route | Direction | Use for | | ----------------------------------------- | --------- | --------------------------------------------------------------------------------------- | | **iNELS 3 export** / third-party protocol | both | visualisation systems, custom integrations | | **MQTT** | both | home-automation platforms, IoT | | **Modbus** | both | industrial equipment, meters, HVAC plant — **RTU needs a CU3-10M; IP works on all CUs** | | **Cloud** | both | phone apps, remote access | **MQTT and Modbus-IP are among the biggest additions since the Rev19 manual**, which covers neither. *** ## 24.2 Exposing devices Whatever the route, external systems only see what you have deliberately exposed. | Setting | Where | Effect | | -------------------------- | ------------------------------------- | -------------------------------------------------- | | **Add to iNELS 3 export:** | system bits, system integers, devices | Makes the object visible externally | | **Read only:** | the same | External systems may read but not write | | **Alias:** | the same | An alternative name for the external system to use | In the **Device manager**, the **Export** tools mark devices in bulk: * **Select all for export** * **Select all for export and use description** * **Unselect all for export** For function block templates there is **Add all to iNELS 3 export** / **Delete all to iNELS 3 export**. > **Expose the minimum.** Every exposed object is something an external system can read — and, unless **Read only** is ticked, write. A visualisation that only shows temperatures does not need write access to your heating outputs. > **Use aliases and keep them stable.** External systems reference objects by name. Renaming an exposed object breaks whatever was reading it. *** ## 24.3 The third-party protocol A plain-text protocol over TCP. Configure it in `[☰]` → **CU configuration** → **Third part setting**: | Field | Meaning | | ------------------ | -------------------------------------------------------------- | | **Port** | TCP port | | **Mode** | Protocol mode | | **Separator** | Field separator character | | **Numeral system** | How numbers are represented | | **Event enable** | Send events as they happen, rather than only answering queries | **Turn Event enable on** if the other system should react to changes. Leave it off if it polls — polling a busy installation is much heavier than pushing events. > Rev19 §20.2 lists the ASCII symbols that survive iNELS 3 export. Consult it if your object names contain accented characters. *** ## 24.4 MQTT Configured in `[☰]` → **CU configuration** → **MQTT setting**: | Field | Meaning | | ------------------------------ | --------------------- | | **Mode:** | MQTT mode | | **User name:** / **Password:** | Broker credentials | | **Version:** | MQTT protocol version | ### What can be published Per `Advance/Documentation/BUS unit to MQTT.txt`: | Category | | | ------------------------ | ------------------------------ | | **MQTT CU Status** | central unit state | | **MQTT Gateway Status** | gateway state | | **MQTT System bits** | your system bits | | **MQTT System integers** | your system integers | | **Units** | around 50 supported unit types | Supported units include the ADC3, DA3 and DAC3 families, the GSB3 and MSB3 button ranges (including the `-V2` and `/S` variants), GRT3-50, IDRT3-1, IM3 inputs, IOU3-108M, JA3 blind actuators, the SA3 relay family, WSB3 units including the `-Hum` humidity versions, GBP3-60, GCH3-31, GCR3-11, GDB3-10, GSP3-100, DMD3-1 and RC3-610M/DALI. **The file in `Advance/Documentation/` is authoritative and ships with your version** — check it rather than this list, which will age. ### Firmware requirement MQTT needs **CU firmware 02.97.02 or later** on CU3-07M, CU3-08M and CU3-09M. Update first — [Chapter 25](/inels-bus/inels-design-manager-idm3/idm3-firmware-update-manager.md). *** ## 24.5 Modbus Three roles: | Role | The CU is | Use for | | -------------------------- | ------------------------ | ------------------------------------------------------------------- | | **Modbus-IP-Master** | the client, over TCP | reading meters and plant — **any central unit** | | **Modbus-IP-Slave** | the server, over TCP | letting a SCADA or PLC read the installation — **any central unit** | | **Internal-Modbus-Master** | master on the serial bus | RTU/ASCII equipment — **CU3-10M only** | | **Internal-Modbus-Slave** | slave on the serial bus | being polled over RS-485 — **CU3-10M only** | Modbus devices are added in the **Device manager** like any other unit, and their values then work in wires and conditions as normal. Notable behaviour from the change log: * Analog **copy** functions work to and from Modbus IP devices * Modbus values support **multiplication** for scaling * **Modbus Address** can be entered in **decimal** as well as hexadecimal * One device can be set as the **default** in a Modbus unit * Modbus units can be published **in MQTT JSON format** [**Chapter 32**](/inels-bus/inels-design-manager-idm3/idm3-modbus-rtu-and-ip-integration.md) **covers Modbus in full** — RTU wiring, master and slave setup, register mapping, third-party integration, and a complete worked example. *** ## 24.6 Cloud `[☰]` → **CU configuration** → **Cloud setting** — **Mode:**, **User name:** and **Password:**. The cloud connection is what phone apps and remote access use. See [Chapter 22](/inels-bus/inels-design-manager-idm3/idm3-central-unit-configuration.md). *** ## 24.7 Choosing a route | You want | Use | | --------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- | | A phone app for the client | **Cloud** | | Integration with Home Assistant, openHAB, Node-RED | **MQTT** | | To read an energy meter or heat pump | **Modbus master** ([Ch. 32](/inels-bus/inels-design-manager-idm3/idm3-modbus-rtu-and-ip-integration.md)) | | To let a building-management system read the installation | **Modbus slave** ([Ch. 32](/inels-bus/inels-design-manager-idm3/idm3-modbus-rtu-and-ip-integration.md)) or **third-party protocol** | | An iNELS visualisation | **iNELS 3 export** | *** ## 24.8 Before you integrate | | | | ------------------------------------------------- | -------------------------------------------------- | | **Check CU firmware first** | MQTT and Modbus-IP both need recent firmware | | **Expose the minimum, and use Read only** | Every exposed object is an attack surface | | **Fix your aliases early** | External systems break when names change | | **Test with the external system before handover** | Integration failures are hard to diagnose remotely | | **Document what you exposed** | Nobody will guess later | *** **Next:** [Chapter 25 — Firmware update](/inels-bus/inels-design-manager-idm3/idm3-firmware-update-manager.md).