His clever solution is to use an Arduino Uno R4 and take advantage of the onboard DAC. To turn on a segment, he connects a segment to a GPIO pin set high while sending 3.5 volts out of the DAC ...

It uses two rows of seven-segment displays to show the current operation and the results. Programming the Arduino Nano to work as an RPN calculator involved a few tricks, though. [Jeroen] wanted a ...