Here is a project I made in the summer of 2025.
On a driving trip from Chicago back home to Seattle, I discovered American Science and Surplus. Their store in Geneva, Illinois has lots of fun stuff, including some two-digit LED displays that I thought I could use to make a neat display.
The circuit in this project multiplexes the displays so they can be driven by the ESP-32. After a few iterations on the breadboard, I got boards done at OSH Park and soldered them up with through-hole parts that I mostly had in my inventory.
The web server on the ESP-32 has two endpoints: one takes a ten-digit hex string, which is a bitmap of the segments to illuminate on the display. The other takes a string of numbers to display -- they're converted from ASCII to their seven-segment representation.
I want to use the project to display some stock prices as they change. Since there's just seven segments, it's a bit crude, but something like "183.78d 1.19" means that the issue I'm tracking is at $183.78 per share, down (for "d") $1.19 per share since the last close.
Right now, all the smarts are in a Python scripts that run on a desktop computer. That script pokes at those endpoints and the ESP-32 just scans the multiplexed displays to show the last thing it was told. Eventually, the device could be standalone, though that comes with a few problems that I'll need to sort out.
Things to do:
- Make the Python script support multiple devices
- Show the DHCP-assigned IP address of the ESP-32 on the LEDs at startup
- Have the ESP-32 beacon a UDP message for automatic discovery by client scripts
- Smarter endpoints: accept characters and decimal points, for example
- Use the on-board LED to indicate stale data -- if no client has made an update in some time
And probably a few more things. But I'm also thinking about 16-segment display with 2 rows of 20 characters for a bit more fidelity ...
This repo contains these directories:
assets: some pictures for the readmeTenDigitPCB: a KiCAD project (including shape and footprint files) for the PCB and its componentsTenDigitsIDF: Visual Studio Code project for the ESP-32 IDF to implement the web server and multiplexingTenDigitQuoter: A Python project (for PyCharm) that shows quotes for a stock from the Yahoo! Finance API
Here are some pictures:
