One of [Kale_3D]’s teachers had made an Arduino-powered calculator. ... Two of the buttons allow scrolling through not only standard arithmetic functions but trigonometric functions also.

However, daily use RPN calculators with large and light touch buttons are rare. So I made it by my own. – This calculator also has trigonometric, logarithmic and exponential functions.

original calculator, which varies from acceptable to atrocious for trigonometric functions involving small angles. Oddly, the calculator started life as a hack on the KIM-1 UNO .