Architecture version 1.

The project of a microcontroller program for an escape room has the following structure:

• config.json
• boot.py
• main.py
• app.py

These files are necessary for making a device for an escape room.

The config.json file contains the configuration of the device.

Key	Description
topic	The topic that MQTT client will subscribe
mqtt_host	The address of MQTT broker
mqtt_user	The login for MQTT broker
mqtt_password	The password for MQTT broker
ssid	The SSID of the wireless network
psk	The Wi-Fi access password

For exapmle:

{
    "topic": "TOPIC",
    "mqtt_host": "HOST",
    "mqtt_user": "USER",
    "mqtt_password": "PASS",
    "ssid": "SSID",
    "psk": "PSK"
}

The microcontroller executes boot.py when it starts. It connects the device to the network using “ssid” and “psk” from config.json. Usually, you should not modify it.

The microcontroller executes main.py when boot.py terminates. It checks a network connection then it tries to connect to the MQTT broker using credentials (“mqtt_host”, “mqtt_user”, “mqtt_password”) from config.json.

If the attempt fails the microcontroller sleeps for a minute, then restarts.

Otherwise, it subscribes on device topic, creates an App instance, calls instance start() method for a time, and executes the infinite loop that periodically checks income messages and calls loop() method of App instance. Usually, you should not modify it.

The App.py file contains the main class of microcontroller escape room application.

class App(client, topic)

App is the main class of microcontroller escape room application. You need to implement it’s methods to make an application.

The arguments are:

• client is a MQTT client.
• topic is a MQTT topic that microcontroller is subscribed.

The __init__ should make this arguments members.

App.on_message(topic, message)

The MQTT messages handler. The main.py calls this method when any MQTT message is received.

The arguments are:

• topic is a MQTT topic that microcontroller is subscribed (as bytearray). To convert to string you need to call .decode('utf-8').
• message is a MQTT message (as string).

Returns None.

App.start()

Make some things after connection to MQTT. Usually, this method sends greating message. You should not initialize peripheral devices here. Do it in __init__ instead.

Returns None.

App.loop()

Make main periodically logic.

Returns None.

File template:

import gc
import utime


class App:
    def __init__(self, client, topic):
        self.client = client
        self.topic = topic

    def on_message(self, topic, message):
        print(topic)
        print(message)
        self.client.publish("micropython", "hello")

    def start(self):
        pass

    def loop(self):
        utime.sleep_ms(1000)
        print(gc.mem_free())