RPN scientific calculator firmware for $13 calculator kit

[gentzel]

Just a quick note that I did try using a STC15F2K60S2 as a drop-in replacement for the IAP15W413AS. No code changes, just an experiment.

It works... sort of. It's flakey. Hard to turn on, when turning off it will often immediately restart by itself, etc. But it's partially functional.

My guess is that there are timing routines or delay loops that would need to be recalibrated for what appears to be a faster processor.