May 23rd - Our First Schematic
I think the best way to get started with this is to work on a simple schematic and, eventually, a PCB. Then, I can start thinking about software, our case, etc. I've been putting things in KiCad slowly, getting the design process started. Today, my school had finals, so I didn't have quite enough time to actually finish anything. But, here is what I have ready right now.
I decided to move forward with the AtMega328P - it has onchip EEPROM to store a handful of programs and has a versitile C programming interface. Plus, it'll be at least thrice as fast as the HP Nut, or an old-timer like the 6208. Unfortunately, that does mean I need to put a programming header on my beautiful board. I've also decided to use a coin cell instead of something rechargable. Given that these machines lasted years (sometimes up to a decade) on a single cell, I think that a CR2032 is the best way to go. Behold, the assortments of components I need (+ key switches and a display) to build the machine. Of course, we'll add more as we go.
I've also decided to use a 128x64 panel - a wider 192x64 would be neat, but is hard to find online. 128x64 is a sacrifice, but I think is well worth it.
An assortment of symbols on a KiCad sheet - something's better than nothing
My family is heading to Spain for a 3 week vacation on Sunday. Not sure if I'll be able to update the log before we leave, but I may work on it a little tommorow morning. I'll update the logs for sure when we get back from Spain, June 16th.
Total time spent: 1.5 hours
May 22nd - Getting started
I've been researching lately about the HP Voyager line of calculators. Something about them seems just so nostalgic, doesn't it. I was looking at purchasing the PX-15C kit to build my own when I realized that there were plenty of features I wanted to add to the calculator. One feature I'm thinking about is fully-automatic impedence calculation, like the Casio fx-61F. Programming features like the HP16C would also be a boon for my retrocomputing projects.
The HP Voyager's 15C - the flagship algebraic calculator
The Casio fx-61F, which can automate impedance calculations
One initial battle I've been fighting is which processor to use. Perhaps the ATMega328P - it is widely used in Arduino Unos, etc. and has plenty of schematics available. Then again, some experience with the 6208 would be nice as well. I'm leaning towards the ATMega328P though, because it doesn't need a seperate RAM, ROM, etc.
Next is choosing a display - the PX-15C uses a 192x64 dot matrix; the HP16C and Casio fx-61F, like most retrocalcs, use single-line displays. A dot matrix would be cool, though. I'm thinking about using a 128x64 panel, which is more commonly avilable than the PX-15C, and resembles the original Voyager form factor. Keyboards are even more problamatic, though: you have to 3D-print and paint one (not sure how that would work).
Tommorow, we're going to work on finding our parts and laying out a schematic, which should be fun. Tedious, sure, but fun.
Total time spent: 3 hours