Walnut casing sets this custom Arduino-powered RPN calculator apart from the crowd

How many of us have a daily tool that is truly unique? Probably not many of us; take a look around your desk and empty your pockets, but more often than not you’ll find that all you have is something almost anyone on the planet could have bought too. But that’s not the case if you have this beautiful custom RPN calculator in a wooden box.

This one comes to us from [Shinsaku Hiura], which usually dazzles us with unique mechanical clocks and displays. This calculator solves a more practical problem – the shortage of RPN calculators on the market with the correct keyboard feel, especially with the large keys and light touch that he wanted. Fittingly, the build began with a numeric keypad, which when freed from its USB interface was reverse-engineered to understand how the matrix was wired. Next, a custom PCB to connect the keyboard to an Arduino and a 20×4 LCD screen was milled, while a test case was designed and printed to verify the assembly. The final case was milled from a solid block of walnut and fitted with an acrylic window, for a clean look with clean lines and pleasing colors.

As for the calculator itself, the demo below shows that it passes the test. The code is smart because it exploits the minimum number of keys available by hiding all scientific and engineering functions behind a “secret silver key” which was once the equal key and obviously not needed in RPN. Hats off to [Shinsaku] for a beautiful and unique addition to his desk.

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