LED Matrix Arrivals

Public transit arrivals on a 128×32 HUB75 LED display, driven by a Raspberry Pi. This is the Python-side renderer that calls the arrivals-kmp CLI for data.

Hardware

Common setup:

• Adafruit RGB Matrix Bonnet
• 2× 64×32 HUB75 RGB LED panels (2.5mm pitch), chained horizontally → 128×32
• 5V power supply (10A recommended to power both panels)

Supported Pi boards:

• Raspberry Pi 5 — uses the Piomatter driver (PIO-based)
• Raspberry Pi Zero 2 W — uses hzeller's rpi-rgb-led-matrix driver via the Adafruit install script

Chaining the panels

1. The Bonnet's HUB75 socket feeds panel 1's IN
2. Run a HUB75 ribbon from panel 1's OUT to panel 2's IN
3. Power both panels from the same 5V rail
4. The library treats the pair as a single 128×32 display via Geometry(width=128, height=32, ...)

If panel 2 appears flipped or mirrored, either flip it physically or change Orientation.Normal to Orientation.R180 in led_matrix.py.

Pi software setup

Raspberry Pi 5

Follow the Adafruit Pi 5 RGB Matrix Panel guide first to install the Piomatter library system deps and udev rules (so /dev/pio0 is accessible without sudo).

Raspberry Pi Zero 2 W

Follow the Adafruit RGB Matrix Bonnet guide and run the install script to compile and install the rgbmatrix Python library.

Install project dependencies

Clone this repo on the Pi and run:

./install.sh

The script detects your Pi model and installs the correct driver. On Pi 5 it installs Piomatter via pip; on Pi Zero 2 it builds the rgbmatrix Python bindings from ~/rpi-rgb-led-matrix into the venv.

Install the arrivals CLI

The Python script calls the arrivals binary from jdamcd/arrivals-kmp. Cross-compile the native CLI for ARM Linux from a macOS or x86 Linux machine:

./gradlew :cli:linkReleaseExecutableLinuxArm64

Then copy the binary to the Pi and put it on your PATH:

scp cli/build/bin/linuxArm64/releaseExecutable/cli.kexe <user>@<host>:/tmp/arrivals
ssh <user>@<host> 'sudo mv /tmp/arrivals /usr/local/bin/arrivals'

Verify on the Pi:

arrivals --json tfl --station 910GSHRDHST --platform 2

You should get a JSON object with station and arrivals fields.

Running

source venv/bin/activate
python arrivals.py "arrivals --json tfl --station 910GSHRDHST --platform 2"

The rgbmatrix driver needs root for GPIO access, so on the Pi Zero 2:

sudo venv/bin/python arrivals.py "arrivals --json tfl --station 910GSHRDHST --platform 2"

Optional: auto-start via systemd

Pi 5 (user service)

There's a template in systemd/arrivals-led.service. To install:

# Edit the ExecStart line to point at your preferred station
mkdir -p ~/.config/systemd/user
cp systemd/arrivals-led.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now arrivals-led
loginctl enable-linger $USER   # So it runs when you're not logged in

Pi Zero 2 (system service, runs as root)

There's a template in systemd/arrivals-led-root.service. To install:

# Edit the ExecStart line to point at your preferred station and user home
sudo cp systemd/arrivals-led-root.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now arrivals-led-root

Parts

I've included a couple of models for 3D-printed parts that might be useful:

• Bracket to connect the 2x LED panels horizontally (with M3 screws)
• Riser to attach a Pi 5 or Pi Zero 2 (with M2.5 & M3 screws)

Tips & troubleshooting

• /dev/pio0: permission denied (Pi 5): The Adafruit udev rule isn't in place. Check the Pi 5 guide's udev section.
• Flicker during data refresh: The LED refresh thread can be preempted by the Linux scheduler, especially when a subprocess is running. Isolating a CPU core helps on both boards:
  1. Append isolcpus=3 to the existing line in /boot/firmware/cmdline.txt, then reboot.
  2. Pi 5 only: Install the patched Piomatter from this branch which pins the blit thread to the isolated core:

     pip install git+https://github.com/lehni/Adafruit_Blinka_Raspberry_Pi5_Piomatter.git@pin-blit-thread-to-isolated-cpu

     See Piomatter PR #79 for details. The rgbmatrix driver picks up the isolated core automatically.
• Colours look wrong: The panels are assumed to be wired in RBG order. If your panels use standard RGB wiring, change RGB_SEQUENCE = "RBG" to "RGB" in arrivals.py.
• Power: If you have any power issues, try powering the Pi separately via its standard USB adapter.

Attribution

The bundled bitmap font was generated based on London Underground Dot Matrix Regular.