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.

There's more detail in this blog post.

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

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 Zero 2 W

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

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).

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 Zero 2 it builds the rgbmatrix Python bindings from ~/rpi-rgb-led-matrix into the venv; on Pi 5 it installs Piomatter via pip.

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 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

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

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 the Raspberry Pi Zero 2 & bonnet (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.