74 lines
2.8 KiB
Markdown
74 lines
2.8 KiB
Markdown
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MQTT Demo
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=========
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The MQTT client can be used to:
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* Publish sensor readings to an MQTT broker.
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* Subscribe to a topic and receive commands from an MQTT broker
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The demo will give some visual feedback with the green LED:
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* Very fast blinking: Searching for a network
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* Fast blinking: Connecting to broker
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* Slow, long blinking: Sending a publish message
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Note that before any MQTT messages can be sent or received you'll
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need to configure an IPv6 connection to the device and assign a routable
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IPv6 address.
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For details how to do this please refer to sections 'Establishing an IPv6 connection'
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and 'Distributing routable IPv6 prefix' in `platform/nrf52dk/README-BLE-6LoWPAN.md`.
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Broker setup
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------------
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By default the example will attempt to publish readings to an MQTT broker
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running on the IPv6 address specified as `MQTT_DEMO_BROKER_IP_ADDR` in
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`project-conf.h`. This functionality was tested successfully with
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[mosquitto](http://mosquitto.org/).
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On Ubuntu you can install and run mosquitto broker using the following
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commands:
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apt-get install mosquitto mosquitto_clients
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killall mosquitto
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mosquitto -p 1883 -v
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Publishing
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----------
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The publish messages include sensor readings but also some other information,
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such as device uptime in seconds and a message sequence number. The demo will
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publish to topic `iot-2/evt/status/fmt/json`. The device will connect using
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client-id `d:quickstart:cc2538:<device-id>`, where `<device-id>` gets
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constructed from the device's IEEE address.
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Subscribing
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-----------
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You can also subscribe to topics and receive commands, but this will only
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work if you use "Org ID" != 'quickstart'. To achieve this, you will need to
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change 'Org ID' (`DEFAULT_ORG_ID`). In this scenario, the device will subscribe
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to:
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`iot-2/cmd/+/fmt/json`
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You can then use this to toggle LEDs. To do this, you can for example
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use mosquitto client to publish to `iot-2/cmd/leds/fmt/json`. So, to change
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the state of an LED, you would do this:
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`mosquitto_pub -h <broker IP> -m "1" -t iot-2/cmd/leds/fmt/json`
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Where `broker IP` should be replaced with the IP address of your mosquitto
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broker (the one where you device has subscribed). Replace `-m "1'` with `-m "0"`
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to turn the LED back off.
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Bear in mind that, even though the topic suggests that messages are of json
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format, they are in fact not. This was done in order to avoid linking a json
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parser into the firmware. This comment only applies to parsing incoming
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messages, outgoing publish messages use proper json payload.
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IBM Quickstart Service
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----------------------
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It is also possible to publish to IBM's quickstart service. To do so, you need
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to undefine `MQTT_DEMO_BROKER_IP_ADDR`.
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If you want to use IBM's cloud service with a registered device, change
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'Org ID' (`DEFAULT_ORG_ID`) and provide the 'Auth Token' (`DEFAULT_AUTH_TOKEN`),
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which acts as a 'password', but bear in mind that it gets transported in clear
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text.
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