This causes false negatives sometimes, boo.

The new 16-bit residual code is a little bit slower, and it shows. I hope I can get this back up soon...

Makes sure the firmware is running as fast as we expect

This seems cleaner, and now logging works before begin()

Our new

This allows the caller to do other things in-between programmed blocks, like showing status.

Now works even when the CPU is stuck in a watchdog reset loop, as it would be when the flash is totally blank.

CSW at this point isn't valid if the error wasn't a timeout but it was something else instead, like a FAULT.

Working on making this reliably halt a chip that's stuck in a watchdog reset loop :(