Build Your Own Scientific Calculator That Doubles as a Macropad

The great thing about being a “maker,” aside from all of the satisfying problem solving and skill building, is that you can create the devices that you wish existed on the consumer market. You aren’t restricted by the same market whims and customer demands that a corporation must consider before pushing the big red button that starts up the manufacturing line. Shao Duan took advantage of that fact to create this DIY scientific calculator that doubles as a 10-key numpad, a macropad, a handheld game console, and a development platform.

This device, imaginatively named the “sci-calc,” is a scientific calculator, first and foremost. It has standard functions for elementary arithmetic, as well has a trigonometric functions — you know, like a scientific calculator. But Duan made it the scientific calculator they always wanted. The most obvious example of that is the use of Kailh choc mechanical key switches, which is the kind of feature that would be hard for a manufacturer to justify, but that is very appealing to the small percentage of us who care about such things. Similarly, there is a big and bright 256×64 pixel OLED screen with plenty of real estate for text and graphics.

That OLED screen makes the sci-calc device fairly practical as a handheld console, too. It won’t compete with a Switch or even an old Game Gear, but it can run a handful of games to help the user pass time between important calculations. Duan has already ported LittleRookChess, SpaceTrash, Snake, and Tetris.

But, arguably, the most useful secondary function is the numpad/macropad mode. The keys are all right there, so this makes a lot of sense. When connected to a computer or device via Bluetooth, it can send standard key presses or macro shortcuts. A layer system expands those capabilities beyond the number of physical keys.

The hardware consists of a custom PCB hosting a ESP32-WROOM-32 microcontroller, which has plenty of processing power for the aforementioned functions. The PCB also includes a CH340C USB-to-Serial chip, an SD card slot, and lithium battery charging circuitry. Duan says that there is room for a lithium battery up to about 1000mAh. The ESP32’s GPIO pins are also accessible, so sci-calc can be used like a development board. The enclosure is just a laser-cut piece of acrylic with standoffs. The key legends are printed on sticker paper.

If you want to build your own sci-calc, Duan uploaded the files to GitHub.