Clem Mayer (AKA MAYER MAKES) used a hefty desk calculator for a decade at his outdated job. One of these calculator’s measurement and full-sized keys make them preferrred for punching in quantity after quantity, day after day. Whereas the essential idea is stable, he thought he may enhance on the thought with an open supply “four-banger” mannequin that features fundamental add / subtract / multiply / divide performance and that runs on batteries, not mains energy.
The ensuing calculator encompasses a 20-key enter setup with Cherry-MX keyswitches and customized 3D-printed keycaps. The switches are wired collectively in a diode-based matrix setup to preserve IO pins, and calculation outcomes are proven on a 20×4 alphanumeric LCD. Energy is offered by way of a pair of AAA batteries, and its case makes use of the lid of a die-cast electronics enclosure as its backside, whereas the highest is 3D-printed.
For processing, Mayer chosen one of many “new” ATtiny collection chips, the ATtiny3226-SU, which provides him a full 32 KB of Flash reminiscence for libraries and code. When all was mentioned and executed, the entire program match onto 8 KB, however, given the completely different ATtiny choices out there, it will be straightforward to swap in a much less succesful (and cheaper) processor if he wanted to avoid wasting on BOM prices.
As demonstrated in direction of the tip of the video, there are just a few limitations to its calculating means per ATtiny’s eight-bit structure. Particularly, it will possibly solely work with numbers as much as a sure measurement, and it solely produces as much as two digits after the decimal place. This, nevertheless, is not an issue for Mayer, and may very well be overcome with a little bit of intelligent programming anyway.
Additional documentation and construct sources can be found if you wish to create your individual, and even increase on its performance.