Backend

Python GPS and Arduino telemetry service for Smart Serow. Connects to gpsd and Arduino serial, buffers data, exposes HTTP API.

Setup

# Install uv if you haven't
curl -LsSf https://astral.sh/uv/install.sh | sh

# Install dependencies
cd pi/backend
uv sync

Run

uv run python main.py

Or for development:

uv run flask --app main run --host 0.0.0.0 --port 5000 --reload

API

Endpoint	Description
`GET /health`	Health check, shows gpsd and Arduino connection status
`GET /gps`	Latest GPS fix (lat, lon, alt, speed, track)
`GET /gps/history`	Last 100 buffered GPS positions
`GET /arduino`	Latest Arduino telemetry (voltage, rpm, eng_temp, gear)
`GET /arduino/history`	Last 100 buffered Arduino readings

Test from SSH

curl http://localhost:5000/health
curl http://localhost:5000/gps
curl http://localhost:5000/gps/history | jq
curl http://localhost:5000/arduino
curl http://localhost:5000/arduino/history | jq

gpsd Setup (Pi)

# Install
sudo apt install gpsd gpsd-clients

# Configure (edit DEVICES to match your GPS serial port)
sudo nano /etc/default/gpsd

# Example /etc/default/gpsd:
# DEVICES="/dev/ttyUSB0"
# GPSD_OPTIONS="-n"
# START_DAEMON="true"

# Restart
sudo systemctl restart gpsd

# Test gpsd directly
gpsmon
cgps -s

Arduino Setup (Pi)

The Arduino Nano connects via USB serial (typically /dev/ttyUSB0 or /dev/ttyACM0).

# Check available ports
ls /dev/tty*

# May need dialout group for serial access
sudo usermod -aG dialout $USER
# Then log out and back in

Arduino Protocol

Production format (JSON at 115200 baud):

{"v":12.45,"rpm":4500,"eng":85,"gear":3}

Legacy text format (also supported):

V_bat: 12.45V
RPM: 4500
ENG: 85C

The parser tries JSON first, falls back to regex for legacy format.

Configuring the Port

Edit main.py to change the default port:

arduino = ArduinoService(port="/dev/ttyACM0", baudrate=115200)

Stub Mode

GPS: If gpsdclient isn't installed or gpsd isn't running, generates fake GPS data
Arduino: If pyserial isn't installed or serial port unavailable, generates fake telemetry

Both services run in stub mode for UI testing without hardware.

Deploy

TODO: Add to scripts/deploy.py as second target + systemd service.