155 lines
6.1 KiB
Markdown
155 lines
6.1 KiB
Markdown
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# ModbusMQTT
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A bridge between Modbus devices and MQTT.
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It is early days, but the plan is:
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* [x] Support custom Modbus transports (Sungrow WiNet-S has been implemented)
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* Modbus RTU has not been tested because I don't have a serial Modbus device, but in principle it should work. Please let me know
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* [x] Support reading input registers
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* [x] Support reading holding registers
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* [ ] Support _setting_ holding registers
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* [ ] Support optional auto-configuration of Home Assistant entities, including using [MQTT Number](https://www.home-assistant.io/integrations/number.mqtt/) et al for holding registers, to allow setting the value.
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* [ ] TLS MQTT connections
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* [ ] WebSocket MQTT connections
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NOTE: For the time being, this does not support MQTTv5.
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## Installing
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For now, use `cargo install` (Rust toolchain required). Soon, I will have release binaries attached to GitHub releases. In the future, there will also be Docker images made available for convenience.
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## Running
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Start the binary, passing in the URL to your MQTT server, including any credentials:
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```sh-session
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$ modbus-mqtt mqtt://$MQTT_HOST[:$MQTT_PORT]/[$CUSTOM_MODBUS_TOPIC]
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```
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The supported protocols are currently just `tcp://`/`mqtt://`, but with intent to support: `mqtts://`, `ssl://`/`tls://`, `ws://`, and `wss://`.
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The default topic which ModbusMQTT monitors and to which it publishes is `modbus-mqtt`. You can vary that by changing the path portion of the MQTT URL.
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Further, you can change other MQTT options by using query params, such as setting a custom client_id:
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```sh
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"mqtt://1.2.3.4/?client_id=$CUSTOM_CLIENT_ID"
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```
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For a full list of supported options, check [the MQTT client library's source code](https://github.com/bytebeamio/rumqtt/blob/c6dc1f7cfb26f6c1f676954a51b398708d49091a/rumqttc/src/lib.rs#L680-L768).
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### Connecting to Modbus devices
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To connect to a Modbus device, you need to post the connection details to MQTT under a topic of `$prefix/$connection_id/connect`. It is intended that such messages are marked as **retained** so that ModbusMQTT reconnects to your devices when it restarts.
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For instance, a simple config might be:
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```jsonc
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// PUBLISH modbus-mqtt/solar-inverter/connect
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{
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"host": "10.10.10.219",
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"proto": "tcp",
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}
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```
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If the connection is successful, you will see the following message like the following sent to the MQTT server:
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```jsonc
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// modbus-mqtt/solar-inverter/state
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"connected"
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```
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#### Full connection examples
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All fields accepted (optional fields show defaults)
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```jsonc
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{
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// Common fields
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"address_offset": 0, // optional
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"unit": 1, // optional, aliased to "slave"
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// TCP:
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"proto": "tcp",
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"host": "1.2.3.4",
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"port": 502, // optional
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// RTU / Serial:
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"proto": "rtu",
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"tty": "/dev/ttyACM0",
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"data_bits": "Eight", // optional (TODO: accept numeric and lowercase)
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// valid: Five, Six, Seven, Eight
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"stop_bits": "One", // optional (TODO: accept numeric and lowercase)
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// valid: One, Two
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"flow_control": "None", // optional (TODO: accept lowercase)
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// valid: None, Software, Hardware
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"parity": "None", // optional (TODO: accept lowercase)
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// valid: None, Odd, Even
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// Sungrow WiNet-S dongle
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"proto": "winet-s",
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"host": "1.2.3.4",
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}
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```
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#### Monitoring registers
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Post to `$MODBUS_MQTT_TOPIC/$CONNECTION_ID/$TYPE/$ADDRESS` where `$TYPE` is one of `input` or `holding` with the following payload (optional fields show defaults):
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```jsonc
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{
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"name": null, // OPTIONAL - gives the register a name which is used in the register MQTT topics (must be a valid topic component)
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"interval": "1m", // OPTIONAL - how often to update the registers value to MQTT
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// e.g.: 3s (every 3 seconds)
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// 2m (every 2 minutes)
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// 1h (every 1 hour)
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"swap_bytes": false, // OPTIONAL
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"swap_words": false, // OPTIONAL
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"type": "s16", // OPTIONAL
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// valid: s8, s16, s32, s64 (signed)
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// u8, u16, u32, u64 (unsigned)
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// f32, f64 (floating point)
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"scale": 0, // OPTIONAL - number in register will be multiplied by 10^(scale)
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// e.g.: to turn kW into W, you would provide scale=3
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// to turn W into kW, you would provide scale=-3
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"offset": 0, // OPTIONAL - will be added to the final result (AFTER scaling)
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// Additionally, "type" can be set to "array":
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"type": "array",
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"of": "u16" // The default array element is u16, but you can change it with the `of` field
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}
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```
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Further, the `type` field can additionally be set to `"array"`, in which case, a `count` field must be provided. The array elements default to `"s16"` but can be overriden in the `"of"` field.
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NOTE: this is likely to change such that there is always a `count` field (with default of 1) and if provided to be greater than 1, it will be interpreted to be an array of elements of the `type` specified.
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There is some code to accept `"string"` type (with a required `length` field) but this is experimental and untested.
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##### Register shorthand
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When issuing the `connect` payload, you can optionally include `input` and/or `holding` fields as arrays containing the above register schema, as long as an `address` field is added. When present, these payloads will be replayed to the MQTT server as if the user had specified each register separately, as above.
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This is a recommended way to specify connections, but the registers are broken out separately so that they can be dynamically added to too.
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## Development
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TODO: set up something like https://hub.docker.com/r/oitc/modbus-server to test with
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## Similar projects
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* https://github.com/Instathings/modbus2mqtt
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* https://github.com/TenySmart/ModbusTCP2MQTT - Sungrow inverter specific
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* https://github.com/bohdan-s/SunGather - Sungrow inverter specific
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