RPi OBD dashboard (+ reverse camera display)

(yes there are too many decimal places on the engine load, I've fixed this in the code)

Hardware

• Raspberry Pi with Bluetooth & Wi-Fi (inbuilt or USB dongle, doesn't matter)
• OBD2 Bluetooth module (buy from eBay, Aliexpress, etc. <$10)
• PiFace Digital to switch video input & detect button presses. I had this lying around, otherwise you can use any kind of relay board and wire your own buttons to GPIO.
• Reversing camera / dash cam with video output
• Display with composite video input

note: composite video is used so I can easily switch outputs with a relay, quality isn't too bad on a small display.

Wiring

Relays: NC (normally closed, i.e. connected by default when Pi is off), CO (common), NO (normally open)

RPi <<<GPIO>>> PiFace
PiFace relay 0/1 <<<NC>>> RPi video out
                 <<<CO>>> Display video in
                 <<<NO>>> Camera video out
                 <<<GND>>> Ground of all cables

Power

I only had one 12V socket available at the front of the car, and the dashcam was already using this, so I took apart the plug, made a small hole and soldered two extra wires to power the 12V display.

The Pi gets power from a USB socket on the CD player meant for flash disks (it apparently provides adequate current, use a USB voltage/current meter to check you're still getting 5+/-0.25V if you're trying such tricks).

Software setup

• Connect module to car
• On the Pi, in a terminal, run:
  • sudo apt update && sudo apt upgrade
  • pip3 install obd PySimpleGUI keyboard
  • git clone https://github.com/trishmapow/obd-gui
• To connect to the module, run:
  • bluetoothctl to enter bluetoothctl shell
  • scan on and scan off once you see your module
  • pair [MAC] where MAC is the address of your OBD module
  • trust [MAC]
  • paired-devices check your module is listed
  • quit to exit bluetoothctl shell
  • sudo sdptool add SP
  • sudo rfcomm connect hci0 [MAC] you should see 'press ctrl+c for hangup'
• Now to see if you can interface with the module:
  • cd into obd-gui
  • python3 gui.py, if you see the numbers and graph updating, great! Otherwise alt-tab to switch to the terminal and see the errors (or exit the app using alt+f4). I had to make some patches to get my module working, you can find them here. Check the troubleshooting guide and issues in the repo. You may have to dig into the pythonOBD source in ~/.local/lib/python3.7/site-packages/obd
• PiFace config steps:
  • unfortunately the apt and pip packages for the piface don't seem to exist anymore, so we have to install manually. git clone both pifacecommon and pifacedigital-io, cd into the directories and run sudo python3 setup.py install for both modules
  • enable SPI in sudo raspi-config, under 'interfacing' (iirc)
  • run sudo python3 piface.py from the obd-gui folder. sudo is required for the keyboard module to work and emulate keypresses
  • try pressing the first button, the relay should switch. The second and third buttons should emulate the left and right arrow keys respectively
• Autostart the apps with the Pi:
  • copy the files in autostart to /etc/xdg/autostart. Make any necessary edits to the desktop files.
  • add your module's MAC address in connect.sh
  • if the scripts complain about missing modules when running with sudo, uncomment the sys.path.append lines at the top of gui.py and piface.py (edit as necessary depending on your Python version, you can run pip3 show obd to see where your package is installed). This is a quick fix solution, there are cleaner ways if you edit sudoers, etc.

Modifying the GUI

The GUI uses the PySimpleGUI library (just about the fastest & easiest way to get a working GUI running). You can adjust the font, refresh rate etc easily by modifying the constants and/or the layout array.

Contributions are welcome, I made the GUI in a rush and focused mainly on functionality.