Pico W Prometheus DHT22 Sensor

A simple temperature and humidity monitoring system using a Raspberry Pi Pico W and DHT22 sensor that exposes metrics for Prometheus monitoring.

What It Does

• Measures temperature and humidity using a DHT22 sensor
• Exposes metrics in Prometheus format for monitoring dashboards
• Web interface for device status and configuration
• Over-the-air updates for easy firmware management
• WiFi connectivity for remote monitoring

Quick Start

Hardware Setup

1. Connect DHT22 sensor to GPIO pin 15 on your Pico W
2. Power the Pico W via USB

Software Setup

1. Flash MicroPython to your Pico W
2. Copy all files from the firmware/ folder to your Pico W
3. Create secrets.py with your WiFi credentials:

   secrets = {
       "ssid": "YourWiFiName",
       "pw": "YourWiFiPassword"
   }

4. Reset the device - it will connect to WiFi and start serving metrics

Using the Device

Web Interface

Once connected, visit your device's IP address in a web browser:

• Dashboard (/) - Overview of sensor status and system info
• Health Check (/health) - Detailed system status
• Configuration (/config) - Change device settings
• Logs (/logs) - View system logs
• Updates (/update) - Update firmware over-the-air

Prometheus Metrics

Add your device to Prometheus configuration:

scrape_configs:
  - job_name: "pico-sensors"
    static_configs:
      - targets: ["<device-ip>:80"] # Replace <device-ip> with your device IP

Metrics available at /metrics:

• temperature_celsius - Temperature reading
• humidity_percent - Humidity reading
• pico_sensor_status - Sensor health (1=OK, 0=FAIL)
• pico_uptime_seconds - Device uptime
• pico_version_info - Firmware version

Configuration

Device Settings

Use the web interface (/config) to configure:

• Device name and location - For metric labels
• OTA update settings - Enable/disable automatic updates
• Update repository - GitHub repo for firmware updates

WiFi Settings

Edit secrets.py to change WiFi credentials, then restart the device.

Monitoring Setup

Grafana Dashboard

Import the included dashboard from configs/grafana-dashboard.json for:

• Temperature and humidity graphs
• Device status monitoring
• System health metrics

Prometheus Configuration

Use the sample config in configs/prometheus.yml as a starting point.

Firmware Updates

Automatic Updates

• Enable in device configuration (/config)
• Device checks for updates periodically
• Updates happen automatically when available

Manual Updates

1. Visit /update on your device
2. Confirm the update
3. Device will restart with new firmware
4. Check /health to confirm new version

Troubleshooting

Device Not Connecting

• Check WiFi credentials in secrets.py
• Ensure WiFi network is 2.4GHz (Pico W doesn't support 5GHz)
• Check device logs at /logs

Sensor Not Working

• Verify DHT22 is connected to GPIO pin 15
• Check sensor wiring (VCC, GND, Data)
• View sensor status at /health

Update Issues

• Ensure device has internet access
• Check logs at /logs for error details
• Updates require ~150KB free memory

Hardware Requirements

• Raspberry Pi Pico W - WiFi-enabled microcontroller
• DHT22 sensor - Temperature and humidity sensor
• Jumper wires - For connections
• Breadboard (optional) - For prototyping

Wiring Diagram

DHT22 Sensor    Pico W
VCC       →     3V3 (Pin 36)
GND       →     GND (Pin 38)
Data      →     GPIO 15 (Pin 20)

Support

For issues or questions:

1. Check the logs at /logs on your device
2. Review the troubleshooting section above
3. Check the GitHub issues page

License

This project is licensed under the MIT License.