Building an HP-35 From the Patent Up

upstart writes:

Remoticon 2021 // Rob Weinstein Builds An HP-35 From The Patent Up:

Fifty years ago, Hewlett-Packard introduced the first handheld scientific calculator, the HP-35. It was quite the engineering feat, since equivalent machines of the day were bulky desktop affairs, if not rack-mounted. [Rob Weinstein] has long been a fan of HP calculators, and used an HP-41C for many years until it wore out. Since then he gradually developed a curiosity about these old calculators and what made them tick. The more he read, the more engrossed he became. [Rob] eventually decided to embark on a three year long reverse-engineer journey that culminated a recreation of the original design on a protoboard that operates exactly like the original from 1972 (although not quite pocket-sized). In this presentation he walks us through the history of the calculator design and his efforts in understanding and eventually replicating it using modern FPGAs.

He started with the original HP patent and began to build tinyFPGA models. One part of the patent was treated as a black box, but he was able to reverse engineer what it does based upon the parts that interacted with it. He made a brief video demonstrating his recreation side-by-side with an actual HP-35.

Rob Weinstein's Remoticon 2021 presentation can be found on YouTube.

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