Fortunately, this has been done for you already in the assignment. See the updated connected-devices/Lampi/lampi/lampi_app.py
The following behavior is critical to understand.
There is a new MQTT topic on the lamp lamp/associated that the Kivy application subscribes to. It expects to receive JSON-encoded messages that are dictionaries of the form
| Device State | Message |
|---|---|
| unassociated | {"code": "da3c72cf84e04f1ab6440132cdf0a087", "associated": false} |
| associated | {"associated": true} |
(where the value of 'code' is just an example value).
When a device is unassociated (associated with the parked_device_user account), the mqtt-daemon will publish a message to that LAMPI's lamp/associated topic with a payload of the form above (with code having a 32 character hexadecimal string and associated having a value of false). The message will be published with QoS of 2 and retained.
When a device has been associated with a user account (Django account other than the parked_device_user account), the Django app will publish a message to that LAMPI's lamp/associated topic with a payload of the form above (with associated having a value of true). The message will be published with QoS of 2 and retained.
When associated, the LAMPI touchscreen behavior is exactly as it has been for previous assignments.
When unassociated, the LAMPI touchscreen behavior changes to displaying a Kivy Popup with a message and the first six characters of the code:
Note: when unassociated and the popup is showing, the LAMPI is unusable. That's not ideal from a UX standpoint, but it simplifies things for the course.
You can update your LAMPI wih the latest code and test this behavior by connecting (via SSH or Serial) and using the mosquitto_pub command (Hint: this is your first testing seam). Probably best not to use Retained messages when testing (otherwise, you have to remember to remove the retained message later).
To simulate an unassociated message:
mosquitto_pub -t "lamp/associated" -m '{"code": "da3c72cf84e04f1ab6440132cdf0a087", "associated": false}'that should cause the popup to be displayed.
You can simulate an associated message:
mosquitto_pub -t "lamp/associated" -m '{"associated": true}'that should cause the popup to disappear and restore the normal LAMPI UI.
The lamp/associated topic must be mapped across the MQTT bridge so that the mqtt-daemon can publish messages to LAMPI. It should be mapped with QoS of 2.
Next up: go to Updating the Django Model and MQTT Daemon
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