Current weather, forecast, and NYC subway train visualization board

Display information you may want to know when leaving the house on a fancy fridge magnet, a.k.a. an LED matrix. Powered by weather.gov and MTA realtime data APIs.

Wondering what everything on this display means? Jump down to the explanation!

Hardware

Components used

• Raspberry Pi Zero W
• 64x32 LED matrix, 5mm pitch – can get cheaper from Aliexpress, but longer shipping time
• Adafruit RGB Matrix Bonnet
• Power supply, 5V 8A
• Mounting tape – (optional) attach Pi to matrix
• Cable concealer – (optional) for power supply cord

Build process

The hardware build is pretty straightforward and mostly involves plugging things in to the right places, unless you want to add an on/off button to the matrix. For Pis without a header, you will need to solder one on. Consider a Raspberry Pi Zero W (or the Zero 2 W) for a smaller form factor. The software commands will take a while to start up vs. newer/faster models, but once they get going I haven't faced any issues.

I followed this tutorial and watched the associated YouTube video for most of the guidance I needed. (The video displays something different in software, but the hardware setup is the same.)

I did make the mod described in the Adafruit RGB Matrix Bonnet documentation under Step 6 to eliminate matrix flicker: soldering a short wire to the bonnet between pins GPIO4 and GPIO18. After making this hardware mod, you need to disable sound on the Pi by following these steps. I didn't bother digging into why this was only an issue with the hardware mod; it doesn't really matter because this project does not involve audio.

Software installation

Tested running:

• macOS on Apple Silicon (with web-based viewer for development)
• Raspberry Pi OS Lite on ARMv6, running on a Raspberry Pi Zero W (with LED matrix connection)

1. npm install
2. (on Pi only) ./scripts/build_rpi-rgb-led-matrix.sh

Note: Package node-canvas is kept at version 2.x because version 3.x fails to build on ARMv6.

Running

Generate board image

npm start

You can also npm run dev with your API key prepended for an auto-reloading server.

Display board on LED matrix (Pi only)

npm run display

Web-based board viewer (for development)

npm run web-viewer

View the board at http://localhost:8000/viewer.html

Explanation of board layout

Click image to enlarge.

Matrix images like this can be displayed with the web-based board viewer mentioned above.

The board only shows trains going in one direction because most of the time I only go downtown from my stop. Not needing to show both directions freed up more space for the weather/forecast visualization.

There are earlier branches of this repo that only display subway departures without weather information:

• subway-only: Cycles through upcoming train departures in large green letters in one direction only, plus a departure timeline like the one on the right of this branch's board.
• no-timeline: Similar to the above, but displays departures in both directions and includes an uptown/downtown arrow. The tradeoff with this branch, as the name implies, is that there was no room for the departure timeline.

Project structure

src/

• index.js: Main entry point for Node.js app that calls the MTA and weather.gov APIs, generates a board image using the JavaScript canvas API, and writes it to disk. It runs in an infinite loop and updates every 30 seconds.
• fetch/: Calling APIs and enriching/transforming responses to the desired formats
• display/: All the display logic for what to draw where
  • board.png: Image of the board to display. Generated the by Node.js app and not in version control. View it on the web viewer or the LED matrix as detailed above under Running.
• constants.js: Constants. STATION_ID is the subway station from which the departures are shown.

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image-viewer.py: Script that recurringly reads the board image file from disk and displays it on the LED matrix using the Python bindings of rpi-rgb-led-matrix. Used Python rather than the faster C++ library because it was more developer friendly (to me) and because the display refresh rate doesn't need to be fast since it only shows a new frame every 30 seconds.

graphics/: Sprite images used on the board, positioned and composited by the Node.js app

scripts/ One-time bash scripts used for dependency installation:

• install_canvas_dependencies.sh automatically runs before npm install to install the required canvas package dependencies. npm install will fail without doing this first.
• build_rpi-rgb-led-matrix.sh builds the binaries for rpi-rgb-led-matrix on Linux OSs with apt-get only. This library displays the board image file on the LED matrix.