* DO NOT USE U300; BAD PIN POLARITY USED! (also true for <=rev3.1!!)

* rev2.0->rev2.1 rework needed:
  * connect U400.6 to U400.7
  * cut connection from U401.10 (to U500.1,R403; but cut close to U401)
  * connect U400.5 to U401.10
  * connect U400.7 to U500.1 ('Vdclo')
  * if U400 not used: connect U400.5 to U400.7

* to update rev2.0 -> rev3.x components:
  * R1,2 -> R500,R405 (reuse component, new part assignment)
  * new: R40{4,3,2}: 47k 0805
  * new: R401: 47k OR 0Ohm; 0805
  * new: R1,R2: 220k 0805
  * new: C401: OPTIONAL 10uF 0603
  * if >=rev3.2: D30{2,3,4,5} is now SOD-123F footprint, not SOD-323

* 3.3 extras:
  * R501 pullup added, kinda needed
  * extra C500, C402 decoupling caps (10nF, 100nF), probably not needed
  * less bottom plane fills around the SMPS
  * still no ESD prot, oh well, PicoEMP doesn't either