HP-41CL Remote Keyboard / Scripting

[rocket.scientist]

(04-25-2021 10:03 PM)Monte Dalrymple Wrote:  

(04-14-2021 10:37 PM)rocket.scientist Wrote:  So I am afraid I already know the best answer is "get a HP-XX instead". I am looking for a facility, likely using HP-IL to do keyboard entry remotely on a HP-41CL. Doing a bit of searching, I am not finding any good options, so I have come to the Oracles for a vision.

This topic came back to mind as I was going through the update process for my CL. After fat fingering a few entries it became evident that this was going to be interesting, with a couple of restarts along the way.

So here is my question. Is remote scripting / remote keyboard entry possible with a 41C class machine?

Thanks for the wisdom.

-Pat (KG5YPQ)

Quick answer, not easily. The keyboard is polled and there are several places where it is checked, even in the OS code. Not to mention that plug-in ROMS do not have to use the OS routines to check the keyboard.

To do this in software would require identifying all of the the places where you might want to inject a virtual keycode/flag and instead call a special subroutine that allowed a poll of the serial port to be substituted.

Doing it in hardware would be much simpler, although that would mean reprogramming the FPGA. All that would be required is the ability to substitute the UART buffer for the keyboard buffer and the receive data available flag for the keyboard flag. This would work no matter where the keyboard scan code resided. It's a fairly trivial change given that the two flags operate essentially the same way relative to data or keycode.

Thank you for that, Monte. I agree with your wisdom that there are advantages to doing this in hardware. While I have possessed the best of intentions to begin digging into your excellent CL FPGA solution, reality always intervenes. Maybe once I decide to fully and truly retire will I have the time to do this.

There has been a lot of good dialog here, and I appreciate the discussion. My take-away is that it is possible to remote control the HP-41, both by bodge and by elegance. And that there is no in-place solution, so we get to be first.

Cool!

-Pat