blinkenxmas.mqtt

The blinkenxmas.mqtt module defines the MessageThread class, the thread used by bxweb and bxcli to communicate with the MQTT broker.

Classes

class blinkenxmas.mqtt.MessageThread(config, queue)

The blinkenxmas MQTT thread class wraps an instance of paho.mqtt.client.Client in a Thread for background execution. Instances of this class may be used as a context manager that will start the thread upon entry, and stop it (re-raising any exception that occurred during execution) on exit. This is the recommended method of running this thread.

Parameters:

• config (argparse.Namespace) – The application configuration

• queue (queue.Queue) – The queue to submit animations to for transmission to the broker

listen()

The “main” routine of the background thread. Retrieves animations from the associated Queue, calls render() to convert them to bytes strings, before posting them to the configured MQTT broker.

stop()

Stop the MQTT background thread.

Support functions

blinkenxmas.mqtt.render(animation, fps, chunk_size=4096)

Given an animation (which is a list of lists of strings of HTML color specifications), and an fps speed, returns a byte-string representation of the animation.

The byte-string returned consists of:

• An unsigned byte containing the fps value

• An unsigned short (2 bytes in network order) containing the number of frames following

• For each frame:

  • An unsigned byte containing the number of LED changes following

  • For each LED change:

    • An unsigned byte with the zero-based index of the LED

    • An unsigned short (2 bytes in network order) containing the color of the LED in RGB565 format

For example, an animation that switches the first and second LEDs between red and blue at 1fps would be rendered as:

b"\x01\x02\x02\x00\xF8\x00\x01\x00\x00\x02\x00\x00\x00\x01\x00\x1F"