HP-41CL Remote Keyboard / Scripting

[Andres]

Many years ago Tony Duell and I discussed (at a very high level, without any detailed design) how to couple a pair of CMOS analog multiplexers (CD 4051 or equivalent) in a back-to-back configuration, and connect them to the rows and columns of the keyboard PCB to load programs into a 42S which, of course, has no other input means. An Arduino (or a Raspberry Pi Pico) could easily drive the muxes to simulate keypresses... the muxes could be located inside the calculator with some glue logic to implement SPI, so to reduce the number of data lines entering the calculator from the outside.

The hardware wand was a product from the HP Optoelectronics division. Such HP wand was sold to OEM, and included little hardware on itself. The sensor was not just a phototransistor but a emitter-detector pair mounted with a hyperbolic lens. The HP 41 Wand was an HP Wand plus the circuitry and ROM needed for its specific function.

Some 45 years ago, a solenoids-based "button pusher" was not as weird as it sounds today. HP used them for quality control in calculators production lines (as shown on a HP Digest issue around 1976-77), and "button pushers" were also advertised to adapt IBM Selectric typewriters as desktop printers.