RPN-duino

[Chasfield]

I stumbled upon an old thread (which I can't now find) in which a forum member had reworked a Texas TI 1025/1050 four banger into a capable RPN programmable. These cheap units were produced in huge quantities and are great for hardware hackers. There is loads of space inside at the thick end, with moulded-in clips for a circuit board. The spacious metal face plate was just made to be re-legended and the keyboard module header lines are robust and accessible with a soldering iron.

Anyway, attached is a picture of my project based on a TI 1025, which now runs an Arduino Nano and 1.3 inch OLED display. This allows a full 4 line output. The original Texas unit featured software on/off switching so I wired a real power switch into the lower casing.

With 24 keys to play with, I was able to add a few extra stack orientated features:

S^2: square all stack registers
1/S: take reciprocal of all stack registers
SS: Sum stack
TVM: loan payment calculator where r=Z, N=Y, PV=X

The build went smoothly and the only problem is that the display is a bit dim for a sunny day thanks to the very heavy filter factor of the grey acrylic cover.