In this thread you say that the 9 digit bubble LED module was defective. Could you explain please? I am currently playing with a Russian 9 digit module that is a clone of the HP, but it is not very bright when a current limiting resistor is used.

https://forum.43oh.com/topic/5524-tms08035-emulating-calculator-build/

Here is a video using 1K, it does not get much better going down to 560R

https://www.instagram.com/p/Bh2_0EcA4YS/

Thanks!

For the 9 digit LED module, it was a bad seller providing defective product with missing + shorted segment / digit lines. I got denied refund / exchange and the seller not even acknowledge the problem. Also impossible to create a kit on non-guaranteed supply source, so I switched to the SparkFun module, which also eventually exhausted.

Seems like the MCU and the LEDs are no longer up to date/out of production. Any recommendation on newer elements to use?

Thanks for the great project!

This is a beautiful project. Definitely one I'd love to build; I never spent much time with the old HP calculators but this might be an excuse to get into that world. Great work, @Chris Chung!

+1000 for your choice of schematic editor. 

This is a finished and mature project. I enter it here after someone advised me on the hackaday prize. The project was done in about 4 months for the 1st cut on last August. I published it on a hp forum http://www.hpmuseum.org/forum/thread-2175.html and got requests for builds / kits. I had since been refined and we managed to deliver 50+ kits / units. I am not active in the creation of kits / units now. And you can find out more via the link.

The project is open sourced and the code (including the very simple ascii schematic, pcb files) are available in my github repository https://github.com/simpleavr/NP25. I can see now this project pages can be expanded to show more details which I will do.

The current design is very tight, in that I used a very entry level MCU to do everything. Even the shift register I need to use one wire for control. But bluetooth (<4.0) via uart is possible. I cannot understand it will be useful though.

As I said, this is a mature project and I don't see any need to expand it. Please feel free to clone it in github and play w/ it.

I also have this NP-41 project what is in a very early stage. It is also entered here in hackaday.io, may be you will also be interested.

/EDIT I forgot to mention that the core emulator is the work of Eric Smith, who wrote the superb Nonpareil simulator. This project is not possible w/o his GNU shared work.

Thank you for posting this. I wasn't aware of all the work you put into these little works of art. Posting this brings this to a broader audience. 

I just wish HP had as much love for the calculators they sold as we do. 

My thought on the bluetooth was to facilitate cuts and pastes between the calculator and a document on a paired computer or a way to create and store programs for up or download. 

I'm an old HP25c fanboy and still have my old HP25c even though it isn't working (original MOS logic fried when I tried to refurbish the charger/ battery pack years ago)

How long have you been working on this?

Will this be open source?

Any thoughts on adding bluetooth to the design?

Do you need any help?