Do I need to learn AC circuits for working with micro-controller projects?
Yes, you need AC.

High-speed microprocessors like those used in boards such as RaspberryPi are running at high speeds &mdash; not DC at all &mdash; and you need to have a solid grounding in things like transmission line theory if you're going to connect one to an external memory chip successfully on a scratch-built board. Not to mention high-speed I/O interfaces such as Ethernet, WiFi, LVDS, etc.

Power conversion circuits that are typically used in such boards also require AC theory in order to calculate things like stability and transient response.

If you really don't want to get involved with that and you prefer to focus on the digital side of things, I would recommend that you work with existing boards and evaluation modules that are available from various vendors. There are hundreds of them out there, and they take care of all of that nasty "AC stuff" for you.



You mention "Arduino" in passing; most things that fall into that category use much slower microcontrollers (tens or hundreds of MHz, rather than GHz+). Anyone and his brother can design one of those boards &mdash; and for the most part, they already have! The only reason to do a custom board would be to make one for a complete specific application.