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