pidashcam 1.0.0.b2

A Raspberry Pi dashboard camera

A python package to deliver dashcam functionality using a Raspberry Pi.

Prerequisites

• various standard libraries

• python-camera

• python-gps

• python-rpi.gpio

Hardware

• Raspberry Pi (I used a Model B+)

• Raspberry Pi Camera Module V2

• Adafruit Ultimate GPS breakout board connected using the UART on GPIO 14 and 15

• UPS PIco with 450mAh battery from ModMyPi. PICo uses GPIO 22 and 27

• Pi Camera HDMI extender from Tindie

• Two momentary push buttons

  • Button A uses GPIO 23

  • Button B uses GPIO 24

• One LED

  • LED1 uses GPIO 16

Functional Overview

• On startup, the camera starts recording to an in-memory buffer of configurable size (default 60s). The video stream is overlaid with current date-time, speed, location and direction of travel.

• LED1 flashes slowly whenever the camera is recording.

• If button A is pressed, the current contents of the buffer are flushed to a file, together with the following few seconds of video. (This can be used to capture the before and after of some event). The camera then goes back to recording into the buffer. LED1 flashes faster whilst the buffer is being saved.

• If button B is pressed, the current contents of the buffer are flushed to a file and recording stopped. LED1 is switched off.

• If button B is pressed again, recording is re-started from new and LED1 flashes slowly again.

• The UPS PIco ensures that recording can continue even if power has been lost (e.g. in a crash)

Syncing videos files from PiDashCam to some other PC/Mac

• In the background, Resilio Sync monitors the folder containing the h264 format video files. If the Pi is connected to my home Wi-Fi, Resilio syncs the contents of the folder to a Mac in the house.

• If the power if switched off (e.g. ignition is turned off) and the Pi is connected to Wi-Fi, the attached UPS keeps the Pi powered for long enough to allow the video files to be synced to my Mac. It then shuts the Pi down gracefully.

• On the Mac, Hazel is monitoring the sync folder. When it sees h264 format files appear, it moves them to another non-syncing folder and converts them to mpeg4 using ffmpeg. By moving the videos to another folder, the limited disk space on the Pi is preserved.

PiDashCam Code Overview

The code comprises an installed system daemon with four threads: 1. Main thread 2. Timer thread that is kicked off as needed 3. Camera thread 4. GPS thread

There are interrupt routines to handle the two buttons.

There are also Events to manage communications to and from the threads

Pseudo Code

Button A interrupt handler (notable event)
  Start Timer thread
  set flushBuffer flag on timeout

Button B interrupt handler (toggle recording)
  If we are recording
    flush the buffer immediately
    clear the recording flag
  Else
    set the recording flag
  EndIf

Camera thread
    While shutdown flag is not set
        While recording flag is set
            Initialise Camera
            start recording into buffer
            While recording flag is set - inner recording loop
                update annotation with current date-time, position and speed
                If flushBuffer is set
                    flush buffer to new file
                EndIf
            EndWhile
        wait for 1 second
    EndWhile
    Exit

GPS Thread
    Initialise connection to gpsd
    While shutdown flag is not set
        add current GPS fix to inter-thread queue
    Exit

Power failure
    Start Timer thread
    set shutdown Event on timeout

Main thread
    Set the record flag
    Kick off Camera thread
    Kick off GPS thread

    While shutdown flag is not set
        wait for 1 second
    While LAN is connected and there are videos in the sync folder
        wait for 1 second
    Kill threads
    Initiate system shutdown
    Exit