Mon Jan 20 10:02:36 EST 2020

STM reset

1. Software reset doesn't work: hangs when erasing flash.  Likely due
   to timer interrupt, though I can't figure out.

2. Power cycle is most robust.  Use this for in-house dev.

3. Hardware reset can be made to work, but requires mod to blue-pill
   board to properly configure the USB pullup.  Current firmware uses
   B5, but this is part of SPI so prob not a good idea.