Engineers Will Love this Dead Calculator Hacked Into a Wireless Keyboard

On the surface, hacking a broken calculator to serve as a Bluetooth ‘keyboard’ for a calculator app on a smartphone seems like hacking for hacking’s sake. But we all know how frustrating a touchscreen keyboard can be for anything but short messages, so for engineers or mathematicians crunching numbers all day, this hack might actually be genius?


Instructables user epostkastl doesn’t go into the gritty details of how this Hewlett Packard 48G scientific calculator’s life came to an end, but it was beyond repair, and ready to be disposed of—or better yet—repurposed. Physically the calculator worked just fine (it clearly hadn’t been run over by a truck or caught in a Bruckheimer-esque explosion) so epostkastl decided it could still be used as a calculator so long as learned muscle memories tailored to its key layout wouldn’t go to waste, but in a more roundabout way

The calculator’s guts were upgraded with an Adafruit Feather nRF52 Bluefruit board which added wireless Bluetooth connectivity but not without the addition of a nightmarish web of wiring and soldering to connect the board to the calculator’s button matrix pins.

It still looks cleaner than the web of wires you’ll find behind my entertainment center.
It still looks cleaner than the web of wires you’ll find behind my entertainment center.
Photo: Instructables

On the smartphone side of things, the HP 48G was recreated using Sébastien Carlier’s open-source Emu48 calculator emulator which allows keyboard presses to be custom-mapped to each of the software buttons. Programming each button to register clicks from its real-life counterpart was undoubtedly a time-consuming process, but the result is arguably a vastly improved emulated calculator experience for someone who can enter equations on one of these blindfolded.

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Reader’s guide for young people: until 1970 the only tools we had to work with numbers were a pencil and a piece of paper. If you were a geek you carried a slide rule, but you still needed pencil and paper to lay out the problem and organize the answer. Graduating in 1971 I did an undergraduate degree in physics with only that. The first pocket calculators reached the market right around then, selling for amazing sums. We gobbled them up as they were so empowering and so cool, like sci fi made real. I saved for a year to buy an HP 35, which featured trig and square root functions, a real breakthrough. It cost $400 in 1972, almost $2,500 today. I still have it.