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Running on a Raspberry Pi

Packages

sudo apt update
sudo apt install python3-venv python3-pip libsdl2-2.0-0 libsdl2-image-2.0-0 \
                 libsdl2-ttf-2.0-0 libfreetype6
# only if you feed the dash over MQTT
sudo apt install mosquitto mosquitto-clients

Checkout and virtual environment

git clone <your-fork> ~/DIGIFIZ
cd ~/DIGIFIZ
python3 -m venv .venv
.venv/bin/pip install -U pip -r requirements.txt

If you will read an Arduino over USB serial, add your user to the serial group and log out and back in:

sudo usermod -aG dialout $USER

Display

The dash takes the panel's own mode and scales the artwork to fit, letterboxing if the aspect ratio differs. Set the mode in /boot/firmware/config.txt; for a typical 5 inch 800x480 HDMI panel:

hdmi_group=2
hdmi_mode=87
hdmi_cvt=800 480 60 6 0 0 0
hdmi_drive=2
disable_overscan=1

Check what the dash decided with:

.venv/bin/python -m digifiz.app --source demo --debug

The overlay reports the display size, the scale factor and the letterbox offset.

No desktop needed

SDL_VIDEODRIVER=kmsdrm draws directly through DRM/KMS, so the Pi can boot to a console with no X11, no Wayland and no compositor. Boot to console with sudo raspi-config → System Options → Boot / Auto Login → Console.

A physical MFA button

Wire a momentary button between a GPIO pin and ground; the internal pull-up means no resistor is needed. Then:

.venv/bin/pip install gpiozero lgpio
.venv/bin/python -m digifiz.app --mfa-button-pin 17

Or set DIGIFIZ_MFA_BUTTON_PIN=17 in the service file. Pin numbers are BCM. Each press steps one mode along; the button is debounced in software, so a plain switch is fine.

If the button is wired to the Arduino instead, send mfabtn=1 and mfabtn=0 in the serial line, or publish to cabin/mfa_next/state over MQTT. All three follow the same mode order.

Service

sudo cp deploy/digifiz.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now digifiz
journalctl -u digifiz -f

Edit the unit's Environment= lines to choose the data source (DIGIFIZ_SOURCE=mqtt|serial|demo|obd) and the broker or serial port.

Memory

All artwork is decoded and pre-scaled once at startup. At 800x480 that is a few tens of MB; at the full 1920x720 the process settles around 160 MB resident, which is comfortable on a 2 GB or larger Pi.

Surviving power cuts

A cluster gets its power cut rather than shut down. The odometer is written atomically (temporary file plus rename) and at most once every 30 seconds, so a cut cannot truncate it. If you want to go further, mount the root filesystem read-only and keep odo.txt on a small writable partition.