mqtt publish example created

examples/06-mqtt-thingspeak/mqtt_publish.py

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+"""
+MicroPython script to read data from a BME280 sensor and
+publish it to ThingSpeak using MQTT.
+
+Authors
+-------
+- Marcelo Rovai, `IoT Made Easy: ESP-MicroPython-MQTT-ThingSpeak <https://towardsdatascience.com/iot-made-easy-esp-micropython-mqtt-thingspeak-ce05eea27814>`_
+- Mike Teachman, `MQTT protocol with Thingspeak using Micropython <https://github.com/miketeachman/micropython-mqtt-thingspeak/tree/master>`_
+- Gunter Spanner, MicroPython for Microcontrollers, ISBN 978-3-89576-436-3
+- Tomas Fryza
+
+Modification history
+--------------------
+- **2024-12-14** : Example created and tested.
+"""
+
+from machine import I2C
+from machine import Pin
+import time
+import bme280
+import network
+import wifi_module
+import config
+from umqtt.robust import MQTTClient
+
+PUBLISH_TIME_SEC = 300
+
+# MQTT parameters
+BROKER_ADDRESS = "mqtt3.thingspeak.com"
+MQTT_CLIENT_ID = "your_client_id"
+MQTT_USERNAME = "your_mqtt_username"
+MQTT_PASSWORD = "your_mqtt_password"
+CHANNEL_ID = "your_thingspeak_channel_id"
+
+# Setup I2C for BME280 sensor
+i2c = I2C(0, scl=Pin(22), sda=Pin(21), freq=100_000)
+bme = bme280.BME280(i2c)
+T, RH, P, _ = bme.read_values()
+
+# Wi-Fi Station interface
+wifi = network.WLAN(network.STA_IF)
+wifi_module.connect(wifi, config.SSID, config.PSWD)
+
+# Setup MQTT client
+# Note: Connection uses unsecure TCP (port 1883)
+client = MQTTClient(
+    server=BROKER_ADDRESS,
+    client_id=MQTT_CLIENT_ID, 
+    user=MQTT_USERNAME, 
+    password=MQTT_PASSWORD, 
+    ssl=False)
+# MQTT topic
+topic = "channels/{}/publish".format(CHANNEL_ID)
+
+# Initialize previous sensor data
+prev_T = T + 10  # Make sure the first readings are published
+prev_RH = RH
+prev_P = P
+
+# Publish sensor data if changed
+def publish_data(T, RH, P):
+    global prev_T, prev_RH, prev_P
+
+    # Check if the data has changed (ignore small fluctuations)
+    # if (T != prev_T) or (RH != prev_RH) or (P != prev_P):
+    if abs(T - prev_T) > 0.1 or abs(RH - prev_RH) > 1 or abs(P - prev_P) > 1:
+        # Prepare payload
+        payload = "field1={:.1f}&field2={:.1f}&field3={:.1f}".format(T, RH, P)
+
+        try:
+            client.connect()
+            client.publish(topic, payload)
+            client.disconnect()
+            print(f"[I] Data published to topic: {topic}")
+
+            # Update previous values after publishing
+            prev_T = T
+            prev_RH = RH
+            prev_P = P
+        except Exception as e:
+            print(f"[E] Failed to publish data: {type(e).__name__}{e}")
+    else:
+        print("[I] No (small) changes in sensor data, skipping publish")
+
+print("[I] Start publishing data to MQTT broker")
+print("[I] Press `Ctrl+C` to stop")
+print()
+
+# Main loop to read and publish data
+try:
+    while True:
+        # Read the sensor data
+        T, RH, P, _ = bme.read_values()
+        print(f"[BME280] temp(°C), humi(%), pres(hPa): {T:.1f}, {RH:.1f}, {P:.1f}")
+
+        # Publish data if it has changed
+        publish_data(T, RH, P)
+
+        # Wait before next reading
+        time.sleep(PUBLISH_TIME_SEC)
+
+except KeyboardInterrupt:
+    # This part runs when Ctrl+C is pressed
+    print("\r\n[I] Program stopped. Exiting...")
+
+    # Optional cleanup code
+    try:
+        client.disconnect()
+    except Exception as e:
+        print(f"[E] Failed to disconnect from MQTT server {type(e).__name__}{e}")
+    wifi_module.disconnect(wifi)