NP-41 Emulator (may be)

[Chris Chung]

(04-14-2016 06:48 PM)Harald Wrote:  

(04-14-2016 04:43 PM)Chris Chung Wrote:  Congrats!! The keypad prints are off on 2 of the rows. Also the fact that I miss 2 traces on the back. I can re-do just the keyboard PCB and since it's within 100mm x 100mm, it will cost <$20 + $10 shipping to get 10 PCBs manufactured. I guess this is the advantage of using two PCBs.

Your photo seems to show the LCD contrast a bit off. You can turn the unit off, turn it back on while pressing "SST", and use "+" and "-" keys to adjust the contrast / bias voltage.

I had given you my old case, w/ the corner mis-formed and also the PCBs "sinks" into the case. If you wish, you can go to http://www.tinkercad.com and search for "NP41 Case", I had made it public so you can tinker w/ it and order a print (locally in your area) via 3dhubs.com. It should cost about $20.

This is very encouraging. Let me know what you think for improvements.

Thanks for the hint about the contrast. It appears there are several,other parameters that can be adjusted, too. At first I had trouble leaving that mode, but then somehow managed. Contrast is better now, but I needed the second lowest setting (on the lowest the display goes blank)

So far I noticed two strange things:

1) using a cat command, the last digit sometimes shows eratic segments while the the calculator displays the catalog.

2) when the calculator has been turned off for a while and then is turned back on, a lot of segments come on that shouldn't. They then fade within a couple of seconds. Is that maybe to do with the charge pump?

I'll continue observing...

Cheers,
Harald

Currently the setup has only the '+' and '-' keys for contrast adjustment. To exit the setup, you need to press "CLX" a couple of times.

1) The ghosting is actually caused by the way the emulation CPU instructs the display for updates. I would thought that it also exists on the original HP-41, again it could also be my implementation did not synchronize w/ the emulated CPU properly. I did not pay attention to CPU timing (emulator), you may want to check the speed compare w/ a HP-41. We are running at 8Mhz right now. I will make available speed steps in the future, it can go to 16 and 24Mhz.

2) I do not experience the same. It is true that upon return from sleep you can see a faint light-up on all the segments when you view it in an angel, but it does not goes away. I don't think it's avoidable. With proper contrast setting it is minimal (on my unit). I am actually quite satisfy w/ the LCD now w/ the charge pump. If it persist on your unit, try to take a couple of photos and I can try and think about what could be causing it. Only thing I can think of is the charge pump capacitor.