NP-41 Emulator (may be)

[Chris Chung]

(04-18-2016 02:21 PM)Harald Wrote:  Here are a couple of observations:

So far I have no news on the display powerup problem. It is nothing to do with the battery. When powerd from a power supply the calculator behaves exactly the same.

Which brings me to the next observation. Current consumption. While turned on the NP41 consumes 1.25mA. Strangely that reduces to 1mA while running a program. Both are good values in my opinion.
However power off consumtion ist at 250µA. Assuming a CR2032 has a capacity of about 200mAh it will be draind in about a month. The MSP430 should be able to do much better in deep sleep.

Shutdown time is rather short compared to my HP41C. I think the NP41 would benefit from making this significantly longer. I can measure times later so we have a propper basis for discussion.

And finaly, timing a simple prime factorisation program, the NP41 is slighly faster than the original. The HP41C takes about 50% longer to finish.

Overall I have not found any serious flaws with the NP41. Thanks for this fantastic project Chris!!

Harald

For the LCD startup ghosting, I really don't have any idea as it never occur to my builds. I can only speculate on the charge pump CAP. The SMD caps are so tiny and there are no labels, etc. I might even have mixed up and sent you a wrong value. If you are able to check it and may be try a higher value.

I hooked up my meter and can confirmed that the sleep is consuming 260uA, which is way too much. I would expect it to be 1-2uA as we are using the LCD driver is a internal peripheral. I will look into it. I might as well be like the NP41s where I forgot to turn off some peripheral.

The auto-off time will be make configurable. Currently it should be 60 seconds.

Thanks for your time commenting on the unit.