HP-25C Eumulator

[Chris Chung]

(11-15-2014 07:17 AM)brouhaha Wrote:  The -41 was originally the primary objective of the DIY series of calculators Richard Ottosen and I developed. Our first four models (DIY0 through DIY3) used PIC microcontrollers, with increasing amounts of memory. Like what you've done, we started with the Woodstock and Spice series. Our conclusion was that even the bigger, faster PIC18 part in the DIY3 wasn't fast enough to make a usable -41 without having to code most of the simulation code in tightly written and highly optimized assember, and even then the speed wouldn't have been great.

Thanks for the heads-up. I am looking at the -41 code as a side project and already see that I need a different processor. Like the way I approach the woodstock, I try 1st to run your core emulation code (modified to platform) on a dev board initially via serial interface. Just to get a feel before designing the I/O aspects of the project.

Quote:...
It's hard to find ANY off-the-shelf display or display module that's the right width for a handheld calculator. Real commercially made calculators all use custom displays, and there's apparently very little market for a calculator-sized LCD as a standard product. It's easy to find LCDs that are either much smaller or much larger than desired for a calculator.
....
I was perfectly willing to use a graphic display with a mostly "normal" bitmap font, rather than trying to replicate the -41 segmented display appearance.

We did find a bitmap graphic LCD module with the same outline dimensions as the Lumex 16x2 character module, but the contract is awful unless a backlight was used.

As my project goal / audience is to create a retro computing toy piece, I really want to achieve as closely to the original look. So far no luck finding anything close.

Quote:On the DIY4, we switched from PIC to Energy Micro Gecko, and later Giant Gecko, which use an ARM Cortex-M3 core. These provide more than enough CPU power for a -41, and that's the first thing I got running on them. The DIY4 originally used the Lumex 16x2 character display. We hacked a 2.7-inch diagonal graphic LCD onto it in place of the character module using an adapter board, which I refer to as the DIY4X and that was vastly superior, but quite expensive. The choice was made beacuse the 2.7" diagonal display was much taller than we wanted, but the width was exactly what we wanted. The price of that graphic LCD has come down somewhat since then. We redesigned the hardare to support the graphic display natively, as DIY5, and I've showed it at conferences in two versions, one running -41 simulation (hacked to optionally show all four stack levels), and one natively running Thomas Okken's Free42 (hacked for an 8-line text display). I polled the conference audience, and there was overwhelmingly more interest in running Free42 than the -41 simulation.

I would think that an ARM core would be an overkill. The TI MSP430 family (being 16 bit) that I am using will offer something in between, and it offers very low power. I got particular interested in the -41 as I was playing w/ a new MCU (TI MSP430FRxx series) that has FRAM memory (data retention as continuous memory) and direct LCD segment driving. And I thought a LCD based calculator would make a nice project to showcase that particular processor.

Quote:Richard and I are still planning to sell calculator hardware similar to the DIY5. It will be able to support several different open-source calculator programs, including Free42, WP-34S, and (eventually) WP-43S. The biggest challenge is that few people are willing to pay what we'll realistically have to sell it for, which is perhaps a bit less than $300. That's about the minimum we can sell it for and not lose our shirts just on the manufacturing cost; the pricing isn't an attempt to recoup any of the costs we've paid out of our own pockets for development, which I estimate to be over $10K so far, and probably at least another $20K to go, nor will it compensate us for any of our time spent, which even at minimum wage amounts to even more than the out-of-pocket expenses.

Yes, I agree it is a limited market. With the need to move to SMD designs and graphic displays, the set-up cost will no doubt be a lot higher. I still has not made the jump due to the investments needed (microscope, re-flow station, etc). And it will not happen if you do not have passion on what you are doing.

Quote:I certainly don't want to discourage anyone from working on such products, but as I've said before, making calculators is a great way to make a small fortune, only if you're starting from a large fortune. It's easy to build prototypes, and extremely difficult to build and sell a commercial-grade product that people will actually buy.

I am in no way trying to make into a commercial-grade product. Just doing a group-buy had me worried (and understand) the quality process. The NP-25 units do not even have a proper case! I have not spend time to do power profiling, regression test, etc. It's really a DIY project and will remain as such. Actually the initial plan was to try create flashy badges (yet functional) for conferences, notice pcb w/ the slot for badge holders, like so



I am not sure how my pursue on the -41 will go. I would definitely try to make your code run on a 16-bit MCU since it's fun to do. But if I couldn't find a "pretty" LCD module the project probably will stop there.

(11-15-2014 12:28 PM)pito Wrote:  When observing today's population starring into their androidal gadgets, quite cheap and powerful today, then I doubt people will buy a calculator (except the enthusiasts and collectors). You may run almost everything on those nice smartphones today..

I agree. From a practical point of view, there are always apps. What I found from my calculator emulator projects, those curious on how things works would appreciate a physical unit over apps. I.e. enthusiasts and collectors. Another target audience group would be handmade crafts and vintage crowd, like as in etsy.com, where people looks for unique and one-of-a-kind items.