NP-41 Emulator (may be)

[Chris Chung]

(01-10-2018 11:31 PM)Guenter Schink Wrote:  Thanks for the update. As said before, take your time, no need to rush.
Günter

Thanks for your patience.

(01-10-2018 11:36 PM)everettr Wrote:  Have you considered a capacitor across the battery as a low-pass filter?

On the PCB, I had 4 pads that I can place low-pass filters, currently I only placed one 100nF. I had been experimenting w/ placing all 4 caps, also w/ some higher values. They really don't make a difference in my testing. After reading / researching on the topic, I am more inclined to think that ground planes are more important as the unit operates on battery only, and I will find out when the new PCBs arrives. I read that w/ increase MCU activity (and speed), the rapid switching on the traces will cause interference, and we do have that happening on key scanning and LCD multiplexing.

Examining the evidence, it is appearing that the bootloader induced memory corruption problem is the main concern. I had very reliably brick a unit just by jiggling the battery on its housing.

The H/W problem is mainly due to workmanship and quality / design of PCB, I think. Both are improving and longer burn-on tests should help.

(01-11-2018 07:41 AM)Massimo Gnerucci Wrote:  I seem to have issues only when I load ROMs: I can usually list one ROM's content fine via CATALOG, but functions, if invoked, aren't executed or, if I load more than one ROM, I can see gibberish interspersed in CATALOG listing.

I need experimenting more.

Yes, this is known to me. And I will spend time to work on it. I don't really quite understand the underlying mechanism other than what I learnt from Eric's code. Will ask the forums help when doing that. The TONE command also does not produce proper frequency, etc. There are many improvements to be made.

Also the next firmware I had added an option to fix the display update logic. Currently I skip some display update calls to save time. There is a lot of segment mapping calculation in the emulator when display need to be updated. I guess in original HP-41C it is partially done in H/W logic so it is fast. The new firmware will allow for full display update and the unit will run slower. But when you do CAT 0,1,2 you will be able to catch the names properly w/o sometimes some names appear on the right.

Please do more experimenting. Just beware of the battery replacing issue. Also let me know what kind of improvements is needed.

In your last few messages, you mentioned some memory problem / finding. I don't understand them but I like to learn (after we fixed the bootloader issue) and work on them. I am really not familiar w/ the HP-41C and only start to write small / simple programs with it.