HP-25C Eumulator

[Chris Chung]

(01-07-2015 10:37 PM)PANAMATIK Wrote:  

(01-07-2015 09:54 PM)brouhaha Wrote:  In Nonpareil ("Eric's code"), I made a serious effort to simulate the instruction-cycle behavior of the HP ACT, including how the display is refreshed one digit per instruction cycle. I did not specifically compare for exact matching of the display flickering, so there might be some differences, though in casual use it seems about the same.

As far as I've seen, Chris has done an excellent job of faithfully adapting the code to the microcontroller.

With the parallel out 74HC164 it is not possible to simulate the exact display behaviour, because the original HP-25 segment driver activated not one digit at a time, but only one segment in one digit at a time. But the human eye cannot distinguish that. The new ACT, also based on "Eric's code", multiplexes the display very exactly and I cannot see any slightest difference.
Bernhard

I agree, w/ the shift register's buffering effect, there is hardware constraint that dictate the differences. My level of "faithful" emulation can only goes to where it had to be ended. I.e. not using same led driving circuitry.

I did tried and explored various option when I design this. If I had used an 28 pin AVR, we don't really need to use a shift register. It was actually a better choice for the project. Except that my design goal is low power and I am more familiar w/ the TI chip. This project to me is more of electronic hobbyist than of HP enthusiast.

The reason I did this project is I had some success doing a TI DataMatch / Sinclair Scientific h/w emulator and in the process searched all the available microcode emulators on the internet. And I found nonpareil, thought I might just make another toy for my daughter to use at school (the Sinclair Scientific's trig function will fail her math tests, I think).

It would be a good exercise for someone to move this to an 328. This would reduce the hardware to just one MCU and allow inclusion of the 34C. Anyone?

(01-07-2015 08:20 PM)walter b Wrote:  

(01-06-2015 03:59 PM)walter b Wrote:  Please count me in for one as well. I might use it in a nonfunctional Woodstock. Ooh, and my soldering skills leave plenty of space for improvement

... thus I'll be grateful for an assembled unit.

d:-)

Mistook that you want to "practice" soldering. My bad

V3 3rd batch list
rposperi x3, Marcus (k), Geoff, jebem (k), walter, Den (8 units)