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61 lines
2.0 KiB
61 lines
2.0 KiB
4 years ago
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# Control your nightlight over the Internet - Virtual IoT Hardware and Raspberry Pi
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In this part of the lesson, you will send telemetry with light levels from your Raspberry Pi or virtual IoT device to an MQTT broker.
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## Publish telemetry
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The next step is to create a JSON document with telemetry and send it to the MQTT broker.
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### Task
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Publish telemetry to the MQTT broker.
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1. Open the nightlight project in VS Code.
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1. If you are using a virtual IoT device, ensure the terminal is running the virtual environment
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1. Add the following import to the top of the `app.py` file:
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```python
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import json
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```
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The `json` library is used to encode the telemetry as a JSON document.
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1. Add the following after the `client_name` declaration:
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```python
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client_telemetry_topic = id + '/telemetry'
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```
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The `client_telemetry_topic` is the MQTT topic the device will publish light levels to.
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1. Replace the contents of the `while True:` loop at the end of the file with the following:
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```python
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while True:
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light = light_sensor.light
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telemetry = json.dumps({'light' : light})
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print("Sending telemetry ", telemetry)
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mqtt_client.publish(client_telemetry_topic, telemetry)
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time.sleep(5)
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```
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This code packages the light level into a JSON document and publishes it to the MQTT broker. It then sleeps to reduce the frequency that messages are sent.
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1. Run the code in the same way as you ran the code from the previous part of the assignment. If you are using a virtual IoT device, then make sure the CounterFit app is running and the light sensor and LED have been created on the correct pins.
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```output
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(.venv) ➜ nightlight python app.py
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MQTT connected!
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Sending telemetry {"light": 0}
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Sending telemetry {"light": 0}
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```
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> 💁 You can find this code in the [code-telemetry/virtual-device](code-telemetry/virtual-device) folder or the [code-telemetry/pi](code-telemetry/pi) folder.
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😀 You have successfully sent telemetry from your device.
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