Imported from GitHub: alexDickhans/ul-temp-sensor · commit 98d383c

Description

Adaptive BLE Sensor Node System

README

Adaptive BLE Sensor Node System

A complete IoT sensor system featuring adaptive power management, BLE communication, and data logging. The system consists of a Raytac MDBT50Q (nRF52840) sensor node and a Raspberry Pi host application.

🏗️ System Architecture

┌─────────────────┐    BLE Advertisement    ┌─────────────────┐
│   Sensor Node   │ ──────────────────────► │  Raspberry Pi   │
│                 │                         │     Host        │
│ • nRF52840      │                         │                 │
│ • BME280        │                         │ • BLE Scanner   │
│ • Battery       │                         │ • Data Logger   │
│ • Adaptive PM   │                         │ • SQLite DB     │
└─────────────────┘                         └─────────────────┘

📋 Features

MCU Firmware (nRF52840)

• Adaptive Power Management: 4-tier power system based on battery voltage
• BME280 Integration: Temperature, pressure, and humidity sensing
• BLE Advertising: Non-connectable advertisements with sensor data
• Deep Sleep: System OFF mode with RTC wake-up
• Battery Monitoring: ADC-based voltage sensing

Raspberry Pi Host

• BLE Scanner: Continuous scanning for sensor advertisements
• Data Decoding: Parses manufacturer-specific data payloads
• SQLite Database: Local data storage with indexing
• Data Viewer: Query and display sensor data
• Systemd Service: Automatic startup and management

🔋 Power Management Tiers

Tier	Battery Range	Wake Interval	BLE Rate	Description
Normal	4.2V - 3.8V	5 minutes	1 Hz	Full performance
Conserve	3.8V - 3.6V	15 minutes	0.2 Hz	Reduced frequency
Reserve	3.6V - 3.4V	30 minutes	0.1 Hz	Minimal operation
Survival	3.4V - 3.2V	60 minutes	0.1 Hz	Critical battery

📦 Hardware Requirements

Sensor Node

• MCU: Raytac MDBT50Q (nRF52840 inside)
• Sensor: Bosch BME280 (I²C)
• Battery: Li-Po pouch (3.7V, 1000mAh+)
• PMIC: BQ25570 (solar charging)
• Connections: I²C, ADC, RTC

Host System

• Platform: Raspberry Pi (any modern Pi with BLE)
• OS: Raspberry Pi OS or Ubuntu
• Storage: SD card with 8GB+ free space

🚀 Quick Start

1. MCU Firmware Setup

# Install nRF Connect SDK
# Follow: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/gs_installing.html

# Clone and build
cd mcu_firmware
./build.sh

# Flash to device
west flash -d build

2. Raspberry Pi Host Setup

# Install dependencies
sudo apt update
sudo apt install python3-pip python3-venv bluetooth bluez

# Create virtual environment
cd pi_host
python3 -m venv venv
source venv/bin/activate

# Install Python packages
pip install -r requirements.txt

# Run scanner
python3 sensor_scanner.py

3. View Data

# List known devices
python3 data_viewer.py --list-devices

# View recent data
python3 data_viewer.py --hours 24 --stats

# Filter by device
python3 data_viewer.py --device AA:BB:CC:DD:EE:FF

📊 BLE Data Format

The sensor node broadcasts manufacturer-specific data with the following structure:

struct sensor_adv_data {
    uint8_t version;           // Protocol version (1)
    uint8_t tier;              // Power tier (0-3)
    uint16_t battery_mv;       // Battery voltage in mV
    int16_t temperature;       // Temperature * 100 (°C)
    uint16_t pressure;         // Pressure * 10 (hPa)
    uint16_t humidity;         // Humidity * 100 (%)
    uint32_t timestamp;        // Unix timestamp
};

Company ID: Nordic Semiconductor (0x0059)

🔧 Configuration

MCU Configuration

Edit mcu_firmware/prj.conf for:

• BLE power settings
• I²C configuration
• ADC settings
• Power management options

Host Configuration

Command-line options for sensor_scanner.py:

• --db: Database file path
• --scan-duration: BLE scan duration (seconds)
• --log-level: Logging verbosity

📈 Data Analysis

Database Schema

CREATE TABLE sensor_data (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    device_address TEXT NOT NULL,
    device_name TEXT,
    timestamp DATETIME NOT NULL,
    temperature REAL,
    pressure REAL,
    humidity REAL,
    battery_mv INTEGER,
    power_tier INTEGER,
    rssi INTEGER,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

Example Queries

-- Average temperature by hour
SELECT strftime('%Y-%m-%d %H:00:00', timestamp) as hour,
       AVG(temperature) as avg_temp
FROM sensor_data 
GROUP BY hour 
ORDER BY hour DESC;

-- Battery status over time
SELECT timestamp, battery_mv, power_tier
FROM sensor_data 
WHERE device_address = 'AA:BB:CC:DD:EE:FF'
ORDER BY timestamp DESC;

🔍 Troubleshooting

Common Issues

1. No BLE advertisements detected

   • Check device is powered and firmware is flashed
   • Verify BLE is enabled on Raspberry Pi
   • Check for interference or range issues

2. High power consumption

   • Verify deep sleep is working (measure current <3µA)
   • Check BLE advertising intervals
   • Monitor battery voltage thresholds

3. Sensor reading errors

   • Check I²C connections
   • Verify BME280 address (0x76 or 0x77)
   • Check power supply stability

Debug Commands

# Monitor MCU serial output
west espressif monitor -d build

# Check BLE devices
sudo hcitool lescan

# Monitor system logs
journalctl -u sensor-scanner -f

# Check database integrity
sqlite3 sensor_data.db "PRAGMA integrity_check;"

🔄 Systemd Service

Create /etc/systemd/system/sensor-scanner.service:

[Unit]
Description=BLE Sensor Scanner
After=bluetooth.service
Wants=bluetooth.service

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi/sensor-system/pi_host
Environment=PATH=/home/pi/sensor-system/pi_host/venv/bin
ExecStart=/home/pi/sensor-system/pi_host/venv/bin/python sensor_scanner.py
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable sensor-scanner
sudo systemctl start sensor-scanner

📚 Development

Project Structure

temp-sensor-code/
├── mcu_firmware/           # nRF52840 firmware
│   ├── src/               # Source files
│   ├── boards/            # Device tree overlays
│   ├── prj.conf          # Zephyr configuration
│   └── build.sh          # Build script
├── pi_host/              # Raspberry Pi application
│   ├── sensor_scanner.py # Main scanner
│   ├── data_viewer.py    # Data query tool
│   └── requirements.txt  # Python dependencies
└── README.md             # This file

Adding New Sensors

1. Extend the sensor_adv_data structure
2. Update the Python decoder
3. Modify database schema
4. Update data viewer

Power Optimization

• Use forced mode for BME280 (not continuous)
• Minimize BLE advertising duration
• Optimize RTC wake intervals
• Monitor current consumption with multimeter

📄 License

This project is open source. See LICENSE file for details.

🤝 Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Test thoroughly
5. Submit a pull request

📞 Support

For issues and questions:

• Check the troubleshooting section
• Review the code comments
• Open an issue on GitHub

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Note: This system is designed for educational and prototyping purposes. For production use, consider additional security measures and environmental protection.