I'm currently using a Atmega328 in a custom PCB project. Unfortunately I'm out of pins, and also want to add USB in the next iteration. I can add USB with the current Atmega328 board using a cheap USB to Serial chip, but my understanding is there are other chips with it built in.
My question is this: what processor do people recommend to upgrade to has more IO pins, hopefully USB included, and also has some room to grow in the future in terms of functionality. I was looking at the Atmega2560, but it's quite expensive compared to the 328. What about some of the newer ARM processors?
Happy to hear anyone's opinions on this - I don't mind having to learn some different ways to code a different chip if it means more options in the future.