Suggestions on HP21 restoration

[Maximilian Hohmann]

Hello!

(04-09-2022 05:13 PM)Marcovecchio Wrote:  Any ideas on how to handle that?

Before re-inventing any wheels you might - if you did not already - want to take a look at Panamatik's "Woodstock Low Power" upgrade: http://www.panamatik.de/html/hp_low_power.html

It is not exactly what you have in mind (you write about a multiline display) but comes close in many other respects, especially in the way it is able to emulate many different calculators.

Only recently we had another thread dealing with an Arduino based recreation of an HP-25 (in one of the other subforums). It was discovered that the 32 bit calculations of the Arduino Nano/Uno and Mega are not good enough to reproduce the precision of the HP calculator. So you will need an Arduino Due (which is way too big to fit into this calculator) or another 64 bit capable microcontroller.

Regards
Max