8.3 Temperature and Humidity Monitoring via @AdafruitIO

In this project, you’ll explore Adafruit IO, a powerful and user-friendly IoT platform. Using MicroPython, your Raspberry Pi Pico W connects to Wi-Fi and integrates with Adafruit IO to demonstrate its real-time communication and control capabilities.

The project features a DHT11 sensor that measures temperature and humidity, sending data to the Adafruit IO dashboard using the MQTT protocol. Additionally, the status of a virtual switch on the dashboard allows remote control of an LED. The code also utilizes the Adafruit IO REST API during setup to synchronize the LED’s state with the hardware, ensuring smooth operation.

By combining MQTT for real-time data exchange and REST APIs for setup synchronization, this project provides an excellent introduction to IoT programming concepts.

1. Build the circuit

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Pico 2 W Starter Kit	450+	Pico 2 W Kit

You can also buy them separately from the links below.

SN	COMPONENT	QUANTITY	LINK
1	Getting to Know Pico 2 W	1
2	Micro USB Cable	1
3	Breadboard	1	BUY
4	Jumper Wires	Several	BUY
5	DHT11 Humiture Sensor	1	-

2. Setting up the Adafruit IO Dashboard

1. Visit Adafruit IO and click Start for Free to create a free account.

   

2. Fill out the sign-up form to create your account.

   

3. Once your account is created, navigate back to Adafruit IO. Click on Dashboards, then select New Dashboard.

   

4. Create a New Dashboard.

   

5. Enter the newly created Dashboard and create a new block.

   

6. Add a Toggle Block to your dashboard.

   

7. Create a new feed for this block. This feed will control the LED, so name it LED.

   

8. Select the LED feed and proceed to the next step.

   

9. Complete the block settings (mainly Block Title, On Text, and Off Text), then click on the Create block button at the bottom right to finish.

   

10. Create two additional Text Blocks to display temperature and humidity. For these blocks, create feeds named temperature and humidity.

    

11. After creating the blocks, your dashboard should look similar to this:

    

12. Adjust the layout as needed using the Edit Layout option.

    

13. Click on API Key to view your username and API key. Make a note of these credentials, as they will be required in your code.

    

3. Run the Code

1. Then, connect pico 2 w board to the computer using the USB cable.

2. Open the 8.3_adafruitio.py file under the path of pico-2w-kit/micropython/iot/8.3_adafruitio, or copy this code into your IDE.

   Note

   This code depends on the lib/umqtt/simple.mpy file. Make sure to upload it to the Pico board before running the script.

   Note

   Before running the code, ensure you have updated the Wi-Fi credentials and Adafruit IO configuration (as mentioned in Step 2.13).

   import network
   import time
   from umqtt.simple import MQTTClient
   from machine import Pin
   import utime
   import dht
   import urequests
   
   # Wi-Fi configuration
   SSID = "your_wifi_ssid"            # modify this
   PASSWORD = "your_password"         # modify this
   
   # Adafruit IO configuration
   AIO_SERVER = "io.adafruit.com"
   AIO_PORT = 1883
   AIO_USER = "your_name_adafruitIO"  # modify this
   AIO_KEY = "aio_xxxxxxxxx"          # modify this
   AIO_FEED_HUM = "humidity"
   AIO_FEED_TEMP = "temperature"
   AIO_FEED_LED = "led"
   
   # DHT11 and LED configuration
   sensor = dht.DHT11(Pin(15))
   led = Pin("LED", Pin.OUT)
   
   # Timestamp for periodic tasks
   last_update = time.ticks_ms()
   
   # Connect to Wi-Fi
   def connect_wifi():
      wlan = network.WLAN(network.STA_IF)
      wlan.active(True)
      wlan.connect(SSID, PASSWORD)
      while not wlan.isconnected():
         print("Connecting to WiFi...")
         time.sleep(1)
      print("WiFi Connected:", wlan.ifconfig())
   
   # Handle received MQTT messages
   def message_callback(topic, msg):
      global led
      message = msg.decode()
      print("Received message on topic {}: {}".format(topic, message))
      if message.lower() == "on":
         led.value(1)  # Turn LED on
      elif message.lower() == "off":
         led.value(0)  # Turn LED off
   
   # Connect to Adafruit IO
   def connect_adafruit():
      client = MQTTClient("pico", AIO_SERVER, AIO_PORT, AIO_USER, AIO_KEY)
      client.set_callback(message_callback)
      client.connect()
      print("Connected to Adafruit IO")
      return client
   
   # Fetch the last value from a feed
   def get_feed_value(feed_name):
      url = f"https://io.adafruit.com/api/v2/{AIO_USER}/feeds/{feed_name}/data/last"
      headers = {"X-AIO-Key": AIO_KEY}
      try:
         response = urequests.get(url, headers=headers)
         if response.status_code == 200:
               data = response.json()
               print(f"Feed {feed_name} last value: {data['value']}")
               return data["value"]
         else:
               print(f"Failed to get feed value: {response.status_code}")
               return None
      except Exception as e:
         print("Error fetching feed value:", e)
         return None
   
   # Main program
   def main():
      global last_update
   
      connect_wifi()
      client = connect_adafruit()
   
      # Subscribe to LED feed
      led_topic = f"{AIO_USER}/feeds/{AIO_FEED_LED}"
      client.subscribe(led_topic)
      print(f"Subscribed to {led_topic}")
   
      # Sync initial LED state
      led_state = get_feed_value(AIO_FEED_LED)
      if led_state:
         if led_state.lower() == "on":
               led.value(1)
         elif led_state.lower() == "off":
               led.value(0)
   
      while True:
         # Check for new MQTT messages
         client.check_msg()
   
         # Update DHT11 data every 10 seconds
         if time.ticks_diff(time.ticks_ms(), last_update) > 10000:
               try:
                  sensor.measure()
                  temperature = str(sensor.temperature)  # Temperature
                  humidity = str(sensor.humidity)        # Humidity
   
                  print("Temperature: {}C   Humidity: {}%".format(temperature, humidity))
   
                  # Publish data to Adafruit IO
                  client.publish(f"{AIO_USER}/feeds/{AIO_FEED_TEMP}", temperature)
                  client.publish(f"{AIO_USER}/feeds/{AIO_FEED_HUM}", humidity)
   
                  last_update = time.ticks_ms()  # Update timestamp
               except Exception as e:
                  print("Error:", e)
   
   try:
      main()
   except Exception as e:
      print("Error:", e)
   

3. Once the code is successfully saved to the Pico and executed, you will see the following message in the serial monitor, confirming successful communication with Adafruit IO.

   

4. Navigate back to Adafruit IO. You can now view the temperature and humidity readings on the dashboard or use the LED toggle switch to control the on/off state of the external LED connected to the circuit.