Build a Raspberry Pi Dashcam: Continuous Loop Recording, GPS Overlay, and Impact-Triggered Save

Commercial dashcams work fine, but they're closed boxes: proprietary apps, cloud upsells, and firmware you can't touch. A Raspberry Pi dashcam gets you the same core functionality — continuous loop recording that never fills the storage card, GPS speed and location overlay burned into the footage, and automatic preservation of the clip around a hard braking event or collision — while staying fully open and hackable. This build uses a Pi, a camera module, a GPS receiver, and an accelerometer to detect impacts, with everything tied together by a Python service that manages the loop-recording ring buffer.

How the System Works

The core design challenge with any dashcam is storage: you can't record continuously forever, so the system needs to record in a rolling buffer of short segments, deleting the oldest segment as it fills up, while still being able to "rescue" a segment permanently when something worth keeping happens. This build handles that with three cooperating pieces:

• Loop recording service: records fixed-length video segments (typically 1-3 minutes) to a dedicated recordings directory, and a background cleanup process deletes the oldest segment whenever free space on the card drops below a threshold, keeping the loop running indefinitely.
• GPS overlay: an NMEA GPS module feeds location and speed data to the recording process, which burns a text overlay (timestamp, speed, coordinates) into the video using the camera's on-the-fly annotation or a post-processing overlay pass.
• Impact detection: an accelerometer (MPU-6050 or similar) is polled continuously in a lightweight loop; when acceleration on any axis exceeds a configurable G-force threshold — consistent with hard braking or a collision — the current segment plus the previous one or two segments are copied out of the loop buffer into a protected folder that the cleanup process ignores.

Wiring

ComponentConnection Raspberry Pi Camera Module (v3 recommended for low-light)CSI camera ribbon connector GPS module (NEO-6M/NEO-M8N, UART)Pi UART TX/RX pins (GPIO 14/15), 3.3V, GND — disable the Pi's serial console first so it doesn't fight over the UART MPU-6050 accelerometer/gyroI2C (SDA/SCL, GPIO 2/3), 3.3V, GND Status LED (recording indicator)Any free GPIO through a current-limiting resistor

Software Setup

1. Flash Raspberry Pi OS Lite to a high-endurance microSD card (or better, boot from a USB SSD — dashcams do heavy sustained write cycles that wear out cheap SD cards fast, and an SSD is worth the extra wiring for this specific use case) and enable the camera and I2C/UART interfaces via raspi-config.
2. Disable the serial console on the UART (raspi-config → Interface Options → Serial Port → login shell: No, hardware enabled: Yes) so GPS data isn't fighting with a login prompt on the same pins.
3. Install libcamera-apps (or rpicam-apps on newer OS builds) for camera capture, gpsd and python3-gps for parsing NMEA sentences from the GPS module, and smbus2 for I2C communication with the accelerometer.
4. Write the recording loop as a Python service using rpicam-vid (or the Picamera2 library) to capture fixed-length segments to a ring-buffer directory, naming each file with a timestamp so segments sort naturally.
5. Write a cleanup daemon that checks free disk space on an interval and deletes the oldest unprotected segment when space drops below a configurable threshold (leave meaningful headroom — don't cut it to the last few MB).
6. Write the GPS overlay logic: either use rpicam-vid's built-in text annotation feature to burn in a live-updating string built from the current GPS fix, or overlay text in a post-processing pass with ffmpeg if you'd rather keep raw footage separately and generate an annotated copy.
7. Write the impact-detection loop: poll the MPU-6050 at a reasonably high rate (50-100Hz is typical), compute the magnitude of acceleration, and when it crosses your threshold, copy the current and previous segment files into a protected/ folder that the cleanup daemon skips.
8. Set all services to start automatically on boot via systemd unit files, so the dashcam is recording within seconds of the car's ignition supplying power — no manual startup step.

Power and Automotive Integration

The Pi needs clean, reliable power that survives the car's ignition cycling and voltage transients. A dedicated 5V automotive USB power supply rated for the automotive environment (not a generic USB charger) is worth the extra cost — automotive-rated supplies handle load dump transients that a cheap phone charger can let through to the Pi's power input. For a cleaner installation, wire through a fused accessory circuit so the dashcam only runs with the ignition on, and consider a small supercapacitor or UPS HAT so the Pi can finish writing the current segment cleanly instead of losing power mid-write when the car shuts off — an abrupt power loss during a file write is the most common cause of corrupted dashcam footage.

Enclosure and Mounting

A simple 3D-printed enclosure mounted to the windshield or dash with a suction or adhesive mount keeps the camera module aimed forward with a clear view. Design the enclosure with ventilation slots — the Pi and camera generate real heat in an enclosed space that sits in direct summer sun, and thermal throttling will hurt frame rates and reliability. Keep the GPS antenna (if external) with a clear view toward the windshield, since GPS reception through a metal roof is poor.

Safety and Legal Considerations

• Windshield mounting laws vary by location — some jurisdictions restrict where on the windshield you can mount a device, particularly regarding obstruction of the driver's view. Check your local regulations before choosing a mounting spot.
• Recording laws vary, including whether audio recording requires consent in two-party consent jurisdictions. If your build includes a microphone, research the wiretapping and consent laws in your area — video-only dashcams are less legally sensitive than ones that also record audio.
• Don't let wiring or the mount itself become a driving hazard — route power cabling neatly along the headliner and A-pillar rather than leaving it draped across the dash or steering column area.
• Footage from a dashcam can be discoverable in legal proceedings (both helpful and unhelpful to you) — understand this before relying on it as a defensive tool, and don't tamper with or represent footage inaccurately if it's ever relevant to an incident.

Testing Before You Rely On It

Before trusting this as your daily dashcam, verify the full loop under real conditions: drive with it running, check that old segments are actually being deleted and the storage doesn't fill up, hit a speed bump or brake hard (safely, with no one behind you) and confirm the impact detection actually preserves the right segments, and check GPS overlay accuracy against your phone's GPS. A dashcam that silently stops recording or fails to save the footage you need it for is worse than not having one, because it creates false confidence.