Hartmut Grawe's Teensy 4.1-Powered LispDeck Puts a Cray-Beating uLisp Supercomputer in Your Pocket

Maker and vintage computing enthusiast Hartmut Grawe has designed a handheld to deliver a wealth of functionality for the Lisp programmer on the go.

"[The LispDeck is a] handheld cyberdeck running entirely on Lisp," Grawe explains. "A large touchscreen, a secondary screen, full USB keyboard support plus rotary encoder, SD Card, RFM69 [radio] and WLAN — all this controlled from a Lisp REPL [Read-Eval-Print Loop] running on the more than capable Teensy 4.1, supported by a built-in fullscreen editor and a small help lexicon."

Developed by John McCarthy in the late 1950s and first implemented as a working interpreter in 1960 by Steve Russell, Lisp is a language well-established but not so broadly known outside its circle of fans. Among those fans is David-Johnson Davies, who created uLisp — a microcontroller-centric version of Lisp, effectively sharing the same relationship to its predecessor as MicroPython and Python.

It's the uLisp project that triggered Grawe's creative urges — initially experimenting with using uLisp on a LILYGO T-Deck but finding the compact screen uncomfortable, so setting out to build something better-suited to his needs. "I began to pursue the idea of creating a Lisp machine that's really usable without ruining one's eyes," he explains, "with a full keyboard and a comfortable editor programmed in uLisp itself that can save and load my work utilizing an SD Card.

"Thankfully, hardware components fitting into that fixed idea are available, so the LispBox came into being as the first iteration: a year 2024 true home computer that 'boots' within seconds into nothing but the [Lisp] REPL prompt, ready to be programmed without PC or tablet support while running at incredible 600MHz."

Having been using the LispBox for some months, Grawe realised that there was a need for something else: a handheld variant, battery-powered and easily-portable for the Lisper on the go. Thus, the LispDeck. Like the LispBox, with which it's compatible, the LispDeck is powered by a Teensy 4.1 microcontroller, connected to an Adafruit RA8875 display controller and 5" touchscreen, a smaller secondary ST77350-based 160×128 TFT display, an Adafruit Radio FeatherWing RFM96 radio module, an Espressif ESP-01S ESP8266 module for Wi-Fi networking, a rotary encoder, and an off-the-shelf detachable wireless USB keyboard, all in a 3D-printed housing.

"Why deviate from the usual and proven Raspberry Pi cyberdeck path at all? Because I really like to be able to completely understand and control the machine down to the last bit like in the aforementioned old days," Grawe explains, "but without being stuck in the eight-bit past. True, theoretically that's possible with the beloved [Raspberry] Pi as well, but only if you're willing to digest millions of Linux source code lines."

"The LispDeck, on the other hand, offers computing oomph miles beyond ancient 'Cray' [supercomputers]," Grawe continues, "on boards the size of a chewing gum stick or less, available at pocket money prices and designed to withstand even clumsy tinkerer's hands like mine."

The project is documented in full on Hackaday.io; source code and 3D-print files have been added to the LispBox GitHub repository under the permissive MIT license.