- 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.

2020.10.20
- sticking with the ADS131A04 and routing the extra two inputs to the header
  means that supporting 2 burn wires for the strand burner daughter card is
  dead simple.  it also means that adding a second load cell and pressure
  sensor if required on a daughter card would also be dead simple.

- for strand burner, I need a daughter card that provides a high-side switch
  for pyro power (since I need a common ground through the system), and has
  resistors for 2 ADC inputs hooked to burn wires.  Bring this all out through
  a 5-pin connector to the outside that hooks to the strand burner end.  We'd
  also use the existing pressure sensor channel, but not use the load cell.

  So, firmware wants to log all 4 analog inputs all the time.  For a test
  stand run, only the pressure sensor and load cell are relevant.  For strand
  burner, pressure sensor and the two burn wires are relevant.

- for Jamie / Estes, I need a daughter card that adds at least 4 thermistor
  inputs, and support for their Sony camera trigger thing.

- 40 pin header and mating female connector for daughter cards w/q1 pricing

	header	Sullins PRPC020DAAN-RC	DK S2011EC-20-ND	0.90	
	mating	Sullins PPPC202LFBN-RC	DK S7123-ND		2.38	

- high-side switch for strand burner daughter card.  This is an 8-SO part
  good to 28V and 21A, 50 mOhm on resistance.  Should be trivial to make 
  work on a 2-layer PCB

	ST's VN7050ASTR, DK 497-15993-1-ND, 1.58

  Means we need multiple header pins carrying pyro voltage to get enough
  current, since the header spec is 3A per pin.  2-4 pins each for v_pyro
  on the pin 1 end, and gnd on the other end should do.

- for strand burner daughter, use CUI TB003-500-P06BE 6-position 5mm pitch
  screw terminal strip, supports 14-26 AWG wire, 10A per pin continuous,
  DK 102-6165-ND, $1.01 q1