Tubes (ZM1180) and driver chips (74141) are inherited. I hade to make this clock (:
I was happy that all the chips were compatible with µC voltage levels.
While concentrating on soldering, i messed up order of numbers. Atleast i did it consistently. As soon i figured out in witch (exactly) way i messed up the firmware could be adjustet.
The Seconds get PWM'd onto the minutes. Every 20 Minutes the tubes get a TubeCare routine or showing the Date.
The Boot-sequence is showing the date 0105 (1.May) then it should display 2020 but the second "2" is not showing up, due to hardcoded year numbers. I made this 3 years ago and didnt thought that far. *facepalm*
btw: isn't that (real) 5 beautiful ? (;