Is there anything other than the crystal and the microcontroller that is necessary for this? I want to get as little as possible, as this is going somewhere and staying there, and doesn't need any shields or accessories. And also, if I wanted to program it just once, is there a way to ghetto-rig it up to a serial port with jumper wires? Thank You!
Maybe I'm not following this. I'm not sure I understand the need to re-invent the wheel. If you are doing this as a DIY to prove to yourself that you can make a controller from ground up complete with a boot load, I would totally understand that, but if you are doing this just to save money, I doubt that you will. You can probably score an aftermarket Arduino nano (for example) for less than $4-5 with free S&H. Are you honestly going to be able to source the parts, pay for postage, construct it, and make your Arduino controller for much less than that? I just find it hard to believe.
If you don't want someone messing with the thing after the fact, desolder the USB port, or even cut that end of the PCB off. Then your project is a set it and forget it. I dunno, that is just my two cents.
