- switches to use are DK CW102-ND

- move switches down box so they aren't spread out into gasket rim area

- add another 2-pin header to PA8 (MCO) so we can sample the master clock to
  calibrate the SOC oscillator, which means moving the RED RF strength LED to
  some other gpio line

2019.10.31
- The more I think about this project, the more I want to go back to a board
  that just does one each load cell and pressure sensor.  I just haven't ever
  actually used anything else.

  Discussion with Joe Bowen made it clear that if I were to design such a 
  board so that it could take option cards, and/or had just a pile of basic
  analog inputs and maybe switch outputs available, that doing other stuff
  could be fun, and we'd "grow the system as we need to".  Every time I tried
  to pin him down on specs, all I got was vagueness.

2020.01.18
- Maybe the right answer is to move to the ADS131A02 which is the 2-channel
  version of the acquisition chip, and costs less.  That would support one
  pressure sensor and one load cell.  Then make it possible to add on other
  acquisition boards somehow.