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+1 on the small 1-2 weekend tangible projects, that you may have wanted to build before, but never got to, they are great for morale. This weekend I implemented RS232-powered RGB LED that is controlled attiny85, which reacts to strings sent to that very same RS232. A gross violation of standard, probably, but it works! It definitely added a lot of joy. I typed “git init” only after I finished the first working versio…
For even more fun with low level breaking of standards, bit-banging rs232 is fun and very doable. Don't use timers for timing either, just spin the cpu the right number of times. :)
One thing that made the development of it all immensely easier was having a Saleae logic analyzer. Highly recommend it (no affiliation, just a happy customer).