Panic Button Emergency Locator

A Raspberry Pi emergency device that turns one deliberate button press into a location-aware SMS alert for trusted contacts.

PEL is a capstone prototype for situations where a phone may be unavailable or too slow to operate. It combines a physical hold-to-arm control, LTE messaging, GNSS location, clear LED/buzzer feedback, and a cancel window in a small offline-first device. The design favors deliberate activation and local operation over cloud dependencies.

When the button is pressed and held, the device acquires a GPS fix via the SIMCOM A7670E LTE module's built-in GNSS, builds a Google Maps link, and sends personalized SMS messages to all configured emergency contacts.

• One-button operation — press and hold for 3 seconds to arm, with a cancel window
• Real-time GPS — GNSS coordinates via A7670E built-in receiver
• LTE SMS delivery — sends alerts over LTE Cat-1 (no 2G dependency)
• Multi-contact support — configurable list of emergency contacts
• Customizable SMS template — personalized messages with contact name, owner name, and map link
• Audio/visual feedback — buzzer patterns and LED indicators for every state
• Local event logging — all panic events logged to file with timestamps and coordinates
• 4-phase safety sequence — hold-to-arm → confirmation → cancel window → execute

Important: The A7670E draws up to 2A during transmission bursts. Use a dedicated regulated 5V supply. Share a common GND with the Pi.

The A7670E communicates over the Pi's hardware UART. On Pi 3/4/5, Bluetooth uses this UART by default and must be disabled.

Add to /boot/config.txt:

dtoverlay=disable-bt
enable_uart=1

Edit /boot/cmdline.txt and remove console=serial0,115200 if present.

Reboot after making these changes:

sudo reboot

sudo systemctl disable hciuart

After reboot, confirm /dev/serial0 exists:

ls -la /dev/serial0

git clone https://github.com/CharlesNaig/PEL.git
cd PEL

pip install -r requirements.txt

This installs:

• pyserial — UART communication with A7670E
• RPi.GPIO — GPIO control for LEDs, relay, and button

Contact details are intentionally excluded from Git. Create a local deployment file:

cp config/contacts.example.json config/contacts.json

Edit config/contacts.json with trusted contacts in E.164 format, then set the owner label without changing tracked source:

export PEL_OWNER_NAME="My PEL Device"

For systemd or a secrets-mounted deployment, set PEL_CONTACTS_FILE to an absolute JSON path. Never commit real contact details, SIM information, or alert logs.

If your wiring differs from the default, update the pin assignments in main/config.py:

PIN_GREEN_LED = 17
PIN_RED_LED   = 27
PIN_RELAY     = 18
PIN_BUTTON    = 22

sudo python3 main/main.py

sudo is required for GPIO access on most Pi configurations.

The system uses a 4-phase safety sequence to prevent accidental triggers:

To cancel: Press the button during Phase 3 (the cancel window). You'll hear a cancel sound and see both LEDs turn off.

During idle, the green LED is solid ON, indicating the system is ready. The main loop polls the button every 50ms.

All settings are in main/config.py:

PEL/
├── assets/               # Portfolio branding
├── config/
│   └── contacts.example.json  # Safe deployment template
├── main/
│   ├── main.py          # Application entry point (setup, loop, shutdown)
│   ├── config.py         # Hardware settings and private contact loader
│   ├── a7670e.py         # A7670E LTE driver (AT commands, GNSS, SMS)
│   ├── buzzer.py         # Relay/buzzer control (patterns, Active LOW)
│   ├── led.py            # LED control (solid, blink, threaded patterns)
│   ├── logger.py         # File-based event logging
│   └── panic.py          # 4-phase panic state machine
├── tests/
│   ├── test_a7670e.py    # A7670E 9-test diagnostic suite + AT terminal
│   ├── test_buzzer_relay.py  # Buzzer pattern verification (6 tests)
│   └── test_led.py       # LED pattern verification (8 tests)
├── requirements.txt      # Python dependencies
└── README.md

Run these to verify individual hardware components before full deployment.

sudo python3 tests/test_a7670e.py

Runs 9 sequential tests:

1. AT communication
2. Module information
3. SIM card status
4. Signal quality (RSSI)
5. Network registration
6. Operator info
7. GNSS power on
8. GPS fix acquisition
9. SMS send (interactive)

After tests complete, enters an interactive AT terminal for manual commands.

sudo python3 tests/test_buzzer_relay.py

Tests 6 buzzer patterns: tick, double beep, cancel sound, success sound, fail sound, and continuous ON.

sudo python3 tests/test_led.py

Tests 8 LED patterns: solid green, solid red, solid both, red blink fast, green blink slow, green blink fast, alternating, and rapid cycle.

• Verify /dev/serial0 exists (ls -la /dev/serial0)
• Confirm dtoverlay=disable-bt and enable_uart=1 are in /boot/config.txt
• Check that console=serial0,115200 is removed from /boot/cmdline.txt
• Ensure the A7670E has a dedicated 5V 2A power supply
• Run sudo python3 tests/test_a7670e.py for diagnostics

• Ensure clear sky view (GNSS needs line-of-sight to satellites)
• First cold fix may take 30–60 seconds; subsequent fixes are faster
• Check that the A7670E's GNSS antenna is connected
• Increase GPS_TIMEOUT in main/config.py if needed

• Verify SIM card is inserted and has SMS credit
• Check signal quality: RSSI should be > 10 (run test_a7670e.py, Test 4)
• Ensure network registration shows "home" or "roaming" (Test 5)
• Verify contact numbers include country code (e.g., +63 for Philippines)

• Confirm GPIO 22 wiring: one side to GPIO 22, other side to GND
• The software enables an internal pull-up resistor; no external pull-up needed
• Check PIN_BUTTON value in main/config.py

• Check RELAY_ACTIVE_LOW in main/config.py matches your relay module
• Verify relay module has separate 5V power
• Run sudo python3 tests/test_buzzer_relay.py to test patterns

• GPIO access requires root: use sudo python3 main/main.py
• Alternatively, add your user to the gpio group: sudo usermod -aG gpio $USER

To start PEL automatically when the Pi boots, create a systemd service:

sudo nano /etc/systemd/system/pel.service

[Unit]
Description=Panic Button Emergency Locator
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/bin/python3 /home/pi/PEL/main/main.py
WorkingDirectory=/home/pi/PEL
Restart=on-failure
RestartSec=5
Environment=PEL_OWNER_NAME=My PEL Device
Environment=PEL_CONTACTS_FILE=/etc/pel/contacts.json

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl enable pel.service
sudo systemctl start pel.service

Check status:

sudo systemctl status pel.service

Released under the MIT License.

Created by Charles Naig as an embedded-systems capstone exploring accessible, offline-first emergency communication.