From time to time we visit the question of how to make a good DIY calculator: the keyboard is a particular sticking point. But a physical keyboard is one of the desirable aspects which distinguishes a physical calculator from an app on a phone or tablet, and the quality of a keyboard can make the difference between a nice calculator and one that's not nice to use.

So, yesterday at the HPCC annual event (incorporating the HHC annual event), held online for the usual reason this year, there were two calculator builds which I found very interesting. One uses the transparent keycaps with labels underneath, and the other uses an ingenious build which adds a click and a keypad to a touchscreen.

Neither build is based on 6502 or '816, but could have been. It's the user interface and construction I'd like to highlight and discuss.

Bookmarks into the day-long video of the proceedings:

Edit: better videos here and here both with subtitles and transcripts.

Eric Hazen's Retro-25 build at 2h50 (Z80-based, VFD display, "relegendable" keycaps on Cherry keys.) Project with photos and slide deck on github.



Michael Park's MP-29 build at 3h18 (Propeller-based, touchscreen showing smart-labelled keys, click-switch underneath, optional perspex/lucite/acrylic key assembly overlay.)

Interesting video. It sounds like he had to overclock the Z80 to get his C code to perform.

I see Michael Park's slides are now also available:
http://www.hpcc.org/conferences/HPCC202 ... ulator.pdf