I'll plead ignorance with your second sentence. AVRs? And why should it depress you that it took me three months? (Keeping in mind that I was taking other classes at the time, and that there was a ton of competition for lab space.)
If what you want is for the code to always have your name on it, you should use a 4-clause BSD license (the original one with the advertising clause).
It's not really a license, it just lets you certify that you are putting your work in the public domain.
AVRs are these fun little cheap microcontrollers; the Arduinos and Chalkroaches, among other things, use them. Writing enough code to drive a couple of on-board UARTs and switch between some real-time processes on an ATMega AVR would be a thing to do in an evening or a week, not three months. So three months to do the same thing due to the unnecessary complexities of PC hardware is kind of depressing! It's a little less depressing if you were only working on it, like, 8 hours a week or something.
That said, it only took a little over a month to build the OS itself, while the other two months I spent working on the train control program. All the equipment is notoriously flaky so coping with real-world brokenness was probably the biggest time sink.