I have finally got my Simple Chess clock in a good usable state. I have received some great help here on the forum with this project and others as well. For this project in particular, I want to give thanks to UKHeliBob, CrossRoads, Nick Gammon, and Coding Badly (for those tiny cores!). Thanks!
The clock uses an SCD55014A display and an Attiny84 processor. I had the enclosure cut at pololu and the pcbs were made at DirtyPCBs.
The clock supports custom time periods and a variety of user-selectable timing modes. All the code and design files are available on Github.
I’ve attached and image here.