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Precision Clock Mk IV

designed this clock years ago, with the intention to incorporate every feature request I ever received for the previous precision clock. However, during the pandemic there was a chip shortage, where these STM32 parts became impossible to acquire.

For one, we'd need a lot of them, to drive our ~150 segments, which would make the PCB layout difficult and the BOM cost increase significantly (regular shift registers are very cheap, but the LED driver chips with settable current are pricey). The idea of taking the clock on a plane, and watching it update as we flew across the timezones, was particularly appealing, but ultimately I decided to keep it in my luggage, as the large red ticking digits do have a resemblance to a cartoon bomb. I did consider adding a charge controller and the footprint for an 18650 holder, which would have turned the clock into a self-contained thing with no cables, but for the vast majority of use cases it's totally fine to connect up a USB battery bank.

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