As I promised in my previous article, I will show you how to connect a temperature sensor to a Raspberry Pi, read real telemetry data, and send it to the Azure IoT Hub:
I am using a Raspberry Pi 4, a DHT11 temperature sensor, and a GPIO Extension Board to connect the sensor to the Raspberry. We’ll be using Azure IoT Python SDK enabling connection to the Azure IoT Hub. And we need DHT11 Python library for reading temperature and humidity from DHT11 sensor on Raspberry Pi.
First, we need to create an IoT Hub and to set up a Raspberry Pi. Repeat the steps described in my article “Connect Raspberry Pi 4 to Azure IoT Hub“:
Connect the sensor to Raspberry Pi
The DHT11 sensor can collect temperature and humidity data. Use the following wiring to connect the sensor to GPIO pins:
| DHT11 Sensor pins | GPIO pins |
|---|---|
| Vcc (+) | 5V (pin 2) |
| Ground (-) | GND (pin 6) |
| Data | GPIO17 (pin 11) |
Turn on your Raspberry Pi and connect it to your network.
Run the application
When it is done, clone the azure-iot-blog GitHub repository into a folder in your Raspberry Pi:
git clone https://github.com/jevgenij-p/azure-iot-blog.gitFind the Python application send_sensor_data.py in the raspberry-to-iot-hub/send-telemetry folder:
import asyncio
import time
import board
import RPi.GPIO as GPIO
import dht11
from azure.iot.device import Message
from azure.iot.device.aio import IoTHubDeviceClient
CONNECTION_STRING = ""
DELAY = 5
TEMPERATURE = 20.0
HUMIDITY = 60
PAYLOAD = '{{"temperature": {temperature}, "humidity": {humidity}}}'
async def main():
try:
# Create instance of the device client
client = IoTHubDeviceClient.create_from_connection_string(CONNECTION_STRING)
# Initialize GPIO
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.cleanup()
# Read data using pin GPIO17
dhtDevice = dht11.DHT11(pin=17)
print("Simulated device started. Press Ctrl-C to exit")
while True:
try:
result = dhtDevice.read()
if result.is_valid():
temperature = result.temperature
humidity = result.humidity
data = PAYLOAD.format(temperature=temperature, humidity=humidity)
message = Message(data)
# Send a message to the IoT hub
print(f"Sending message: {message}")
await client.send_message(message)
print("Message successfully sent")
else:
# print("Error: %d" % result.error_code)
continue
await asyncio.sleep(DELAY)
except KeyboardInterrupt:
print("Simulated device stopped")
GPIO.cleanup()
break
except Exception as error:
print(error.args[0])
if __name__ == '__main__':
asyncio.run(main())
IMPORTANT
Make sure you copy-paste the Primary Connection String you saved when you created your IoT device, into the quotes in the Line 9.
Now, open your Raspberry Pi terminal and install Python packages:
pip3 install azure-iot-device
pip3 install asyncio
pip2 install dht11Run the application:
python3 send_sensor_data.pyIf everything is configured and connected correctly, the program will be sending sensor data every 5 seconds to your IoT hub:
Open Azure Portal, find your IoT hub, and select Overview in the left navigation menu. You should see number of messages received by your IoT hub from your device:
Stay tuned. I’ll continue the “Azure IoT” series.
Jevgenijs Pankovs 
pi@raspberrypi:~/azure-iot-blog/raspberry-to-iot-hub/send-telemetry $ pip2 install dht11
Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
Collecting dht11
Could not find a version that satisfies the requirement dht11 (from versions: )
No matching distribution found for dht11
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pi@raspberrypi:~/azure-iot-blog/raspberry-to-iot-hub/send-telemetry $ python3 send_sensor_data.py
Traceback (most recent call last):
File “send_sensor_data.py”, line 5, in
import dht11
ModuleNotFoundError: No module named ‘dht11’
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Sorry Yhhaw for the typo. It should be:
pip3 install dht11
I’ve been using DHT11 Python library: https://pypi.org/project/dht11/
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Great. It works! Thank you very much.
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Is there DHT22 Python library?
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As to the DHT22 library, you can use adafruit library. You can find all the details in my article “How to make a thermometer”: https://jev-pankov.com/2021/03/27/how-to-make-a-thermometer/
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Thanks for the help. I tried to use the code in DHT22 article and “blend” into code in DHT11 article, but it didn’t work.. is it possible to check my code and correct my mistakes?
Here is my code:
import asyncio
import time
import board
import adafruit_dht
from azure.iot.device import Message
from azure.iot.device.aio import IoTHubDeviceClient
CONNECTION_STRING = “XXXX”
DELAY = 5
TEMPERATURE = 20.0
HUMIDITY = 60.0
PAYLOAD = ‘{{“temperature”: {temperature}, “humidity”: {humidity}}}’
async def main():
dhtDevice = adafruit_dht.DHT22(board.D4, use_pulseio=False)
print(“Measurement started. Press Ctrl-C to exit”)
while True:
try:
temperature = dhtDevice.temperature
humidity = dhtDevice.humidity
data = PAYLOAD.format(temperature=temperature, humidity=humidity)
message = Message(data)
# Send a message to the IoT hub
print(f”Sending message: {message}”)
await client.send_message(message)
print(“Message successfully sent”)
except KeyboardInterrupt:
dhtDevice.exit()
raise SystemExit
except RuntimeError as error:
print(error.args[0])
time.sleep(DELAY)
continue
time.sleep(DELAY)
if __name__ == ‘__main__’:
asyncio.run(main())
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