Getting function not found errors when uploading code

Thanks for confirming it should be right to go to at least 3.3V +Gordon.

The troubleshooting page is where I figured out how to reflash and boot to an empty program from.

I'm going to stick with a much bigger voltage divider gap (and less accuracy in the range I care about for now).

I'm also getting a more accurate multimeter on the off chance that's the issue :)