Developer David Johnson-Davies has built a wireless alphanumeric message display with a difference: the code, running on a Raspberry Pi Pico W, is written in Lisp.
"This is a wireless message display based on a Raspberry Pi Pico W and written in Lisp," Johnson-Davies explains of the project. "You can send a message to it via Wi-Fi from a web browser on a mobile phone or computer, and it’s displayed on an eight-character alphanumeric display. You could use it for reminders, or short messages to another person in your household."
The addition of Wi-Fi connectivity — with Bluetooth expected to follow in a future firmware update — to the popular low-cost Raspberry Pi Pico microcontroller development board has made it a great choice for network-connected messaging projects like this, but the majority are based on MicroPython, CircuitPython,or C/C++. Johnson-Davies' implementation goes in a different direction, using the microcontroller-focused Arm build of uLisp instead.
"The latest version of Arm uLisp, Version 4.2, […] contains the wireless extensions for the Raspberry Pi Pico W," Johnson-Davies explains. "The simplest way to install the Wireless Message Display program is to open the Arduino IDE Serial Monitor, copy the entire text of the program from the link at the end of this article, paste it into the Serial Monitor input box, and press return."
Once installed, the code provides a web server with a simple messaging interface accessible via an HTTP GET request: Enter up to eight characters — chosen from those suitable for use in a URL — as a query after a question mark, and it will immediately appear on the two connected four-character LED displays. Should your message need a space, Johnson-Davies notes, the underscore can be used.
"It's quite fun thinking how to express messages in eight characters," Johnson-Davies says, "but if this seems a bit restrictive you could display longer messages by making them scroll along the display."