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brouhaha · 09-29-2015, 07:08 PM

(08-26-2015 06:48 PM)Bill (Smithville NJ) Wrote: Well, it's been a long long long time of "Hanging in there". The 43S was mentioned back in a 2005 post and the feature set and keyboard layout has been hashed to death.

There may have been *something* mentioned with a proposed 43S designation in 2005, but AFAIK there wasn't any serious work on it until I demonstrated potentially suitable prototype hardware in Sept. 2011. For the last four years Richard Ottosen and I have been working on that. I'll describe some history of the project, then an update on the status.

Richard and I have been working since 1995 on calculator hardware intended to support open-source firmware. Progress has been very slow because this has been a spare-time project, and both of us have a lot of other demands on our time.

We've demonstrated a succession of prototypes starting around 2004, named DIYn. (There were actually two prototypes from the 1990s, which I've retconned "DIY0".) Our original design target was to provide the functionality of the HP-41CX, either by reimplementing the feature set, or by running the actual HP-41CX firmware. Our earliest hardware didn't have enough memory or a fast enough CPU to do that, so they ran firmware from Woodstock and Spice series calculators instead. We demonstrated these at HHC conferences.

DIY1, DIY2, 2003-2004:
https://www.flickr.com/photos/22368471@N...8841933989

DIY3, 3D-printed case, 2009:
https://www.flickr.com/photos/22368471@N...9238179642

From 2003-2010, microcontrollers with enough memory and fast enough CPU to achieve our objectives would drain lithium coin cells quickly, and we did NOT want to build calculators that required larger batteries or frequent recharging of batteries. In 2010, a low-power ARM microcontroller became available, and we designed new prototypes which could run the HP-41CX firmware:

DIY4 hardware with character LCD, running HP-41CX firmware, July 2011:
https://www.flickr.com/photos/22368471@N...8726860797

DIY4 with kludge to evaluate graphic LCD, running HP-41CX firmware hacked for full stack display, August 2011:
https://www.flickr.com/photos/22368471@N...8726406755

DIY4X (DIY4 using adapter board for graphic LCD), September 2011:
https://www.flickr.com/photos/22368471@N...8413263533

The ARM microcontroller chosen for the DIY4 had 128KB of flash and 32KB of RAM, which still wasn't as much as we needed for a 41CX fully configurable with user-selectable modules in all ports. A new version of the microcontroller became available that had 1MB of flash and 128KB of RAM. We were able to install that in the existing DIY4X. The new chip also added USB support, which we were able to use by redesigning the display adapter board.

DIY4X using new display adapter board that adds USB capability, January 2012:
https://www.flickr.com/photos/22368471@N...8726780827
https://www.flickr.com/photos/22368471@N...8704955497
https://www.flickr.com/photos/22368471@N...8726621113

I ported Thomas Okken's Free42 software to run on the DIY4X hardware. The DIY4 keyboard layout, having been designed for the HP-41CX, was not very suitable for Free42, so the keys had to be rearranged somewhat randomly, making it difficult to use. I modified the Free42 software to have a seven-line display with dedicated soft menu legends, rather than the two lines of the original, one of which was often used for soft menus, leaving only one line for stack or program line display.

https://www.flickr.com/photos/22368471@N...8851996198

Around this time frame, I asked the WP-34s firmware developers whether they might be interested in this hardware platform. Walter started working on a WP-43s design based on our hardware specifications.

At an HHC conference, I conducted market research by asking attendees whether they'd be more interested in a new calculator that was functionally an improved 41CX, including the four-line stack display, or a 42S. The show of hands was overwhelmingly for the 42S. I repeated this poll at the latest HHC conference, and the result was the same.

We redesigned as the DIY5, using a single PCB, eliminating the need for the display adapter, and changed the keyboard layout to be better suited to the 42S, with one additional row of keys so that we could have permanently dedicated soft menu keys, rather than menu keys shared with common scientific functions. The packaging was changed to make the calculator roughly two thirds the thickness of the DIY4X:

https://www.flickr.com/photos/22368471@N...8853138738

The DIY5 PCB had a number of minor design errors, and we decided to make some minor improvements to it including better support for IR printing. The revised hardware is called XC-40. We tried to have a near-final rev of the XC-40 hardware built in time for the recent HHC 2015 conference, and to have sent out prototypes to the WP-34s developers before the conference, but unfortunately we didn't quite pull that off. We now have the components on hand to build ten units, but due to unforeseen circumstances the PCB layout isn't quite ready.

We expect to have the new PCB layout completed soon, build one unit for hardware validation, and if all goes well build more units for firmware development. We expect to make units available to the WP-34s developers before year end.

The development of WP-43s firmware is not going to happen overnight. In fact, it might take quite a while. The firmware developers have said that they don't have as much time available as they did when developing WP-34s.

In the mean time, I'm working on porting WP-34s to the XC-40 hardware.

We hope to get the XC-40 hardware through EMC testing (FCC part 15), and to offer XC-42 firmware development prototypes (XC-40 hardware with Free42 firmware) for purchase by enthusiasts in the spring. The prototypes will have the folded polyester film case shown in the DIY5 photographs, with a photo paper keyboard overlay over the tact switches. It will be possible to flash other firmware (via USB or MicroSD card) and replace the keyboard overlay, to run WP-34s, or (someday) WP-43s.

If I'm able to get suitable CAD designs whipped into shape, the STL files will be made available so that those wanting a 3D-printed case can print their own case parts or order them from one of the online 3D printing services. The 3D case design will be somewhat similar to that seen in the DIY3 photos, but wedge shaped (thinner at the keyboard end, thicker at the display end) to use a pair of alkaline AA cells for longer battery life, and to allow at least a little bit of usage of the MicroSD card under low battery conditions. (Even when they are fresh, CR2032 lithium coin cells can barely power the MicroSD card. When they are nearly at end of life, the current drawn by the MicroSD card when active could cause a calculator reset and memory loss.)

Because the LCD display is attached by double-sided adhesive foam to the XC-40 PCB when installed in the folded polyester film case, and is damaged if the foam is removed, it might be necessary to purchase a replacement display when refitting the calculator into a 3D-printed case. The LCD display costs approximately $34 each in single quantity from Digi-Key or Mouser.