* This design is based on the modem section of Openmoko's GTA02-MB-A6 board;
  the modem section consists of all components that are enclosed within the
  metal shieldcan footprint with reference designator SH1.  Nothing else
  besides this modem section is reused from Openmoko's PCB, hence all other
  pre-existing components should be deleted from the PCB design as the first
  order of business.

* The reference designators used in the present design (i.e., in the new
  netlist to be imported) are not the same as those used by Openmoko.  Instead,
  this design uses the refdes numbering scheme from TI's Leonardo schematics.
  However, because Openmoko's design is clearly based on the same Leonardo, the
  solution is to renumber the reference designators in Openmoko's PCB file
  before using it as the basis for the present derived board.  A PADS ASCII
  version of GTA02-MB-A6 with reference designators suitably renumbered can be
  found here:

  https://www.freecalypso.org/devboard/GTA02-MB-A6_renumbered.asc

* The following 116 components of the present design correspond directly to
  the same-named components in the renumbered GTA02-MB-A6:

  C201, C202, C203, C204, C205, C208, C209, C210, C211, C212, C213, C214, C215,
  C216, C217, C218, C219, C220, C221, C223, C224, C225, C226, C253, C295, C296,
  C318, C322, C401, C402, C403, C404, C405, C406, C407, C408, C409, C410, C600,
  C606, C607, C608, C609, C610, C613, C616, C617, C619, C620, C622, C628, C629,
  C630, C631, C632, C633, C634, C648, C651, C652, C653, C654, C655, C656, C680,
  C681, C682, C683, C684, C698, D200, L401, L402, L403, L404, L405, L406, L600,
  L601, L680, Q401, Q402, R106, R204, R206, R207, R208, R209, R210, R211, R215,
  R216, R217, R251, R270, R295, R296, R328, R370, R600, R601, R604, R621, R622,
  R623, U201, U202, U301, U401, U402, U403, U404, U602, U603, X201, X202

  With a only few minor exceptions outlined in these notes, the interconnections
  between these components in the present design are exactly the same as they
  were in the GTA02-MB-A6, therefore the entire PCB layout section consisting
  of these components should be kept as unchanged as possible.

* The following 40 components are new to the present design, i.e., do not
  originate from GTA02-MB-A6:

  C306, C310, C312, C314, C315, C316, C319, C323, C330, C331, C332, C335, C363,
  J301, J302, J305, J308, J310, J311, J312, JP1, K301, K304, MIC1, Q308, R100,
  R101, R102, R103, R104, R105, R107, R322, R329, R331, R332, R338, R351, R352,
  U302

  Of these 40 components, 24 have PARTTYPEs that are the same as some already
  existing PART in the modem section of GTA02-MB-A6, so their import should be
  straightforward.  Only 16 of the new components have new PARTTYPEs:

  C323 TAN-R-1000u-6V3-SPRAGUE
  J301 HEADER_5x2
  J302 SIM_SOCKET
  J305 WEIDMULLER_1510460000
  J308 SMA_FEMALE_RIGHTANGLE
  J310 HEADER_7x2
  J311 HEADER_5x1
  J312 HEADER_2PIN
  JP1 HEADER_2PIN
  K301 PUSHBUTTON_DEVBOARD
  K304 PUSHBUTTON_DEVBOARD
  MIC1 TOM-1242L-NF-R
  Q308 UMD9N
  R322 R_2K7_0402
  R329 R_47R_0402
  U302 TPA6203A1DRB

  The PARTTYPE names for these new components have been assigned completely
  arbitrarily; if the PADS person prefers different names, I can trivially
  change them to whatever is desired by editing the MCL and regenerating the
  netlist.

* For the 16 new components with new PARTTYPEs, please see the detailed
  descriptions of these components in the MCL file in order to select or draw
  the correct PCB land patterns.  The headers can be either through-hole or
  SMT, whichever is more convenient for the PCB layout, and the two dual-row
  headers shall use ribbon cable pin numbering.

* The compiled netlist in pads-import-netlist.asc is the new netlist for the
  board as a whole; it captures both the interconnections within the core
  section (which are expected to exactly match those in Openmoko's PCB layout,
  modulo a few explicitly listed exceptions) and the connections from various
  components in the core section to the peripherals added for this development
  board (mostly interface connectors).

* Not being a PADS user myself (I have neither a copy of the PADS software
  itself nor a Windows machine to run it on), I had to construct the PADS
  netlist file for import blindly.  If there are any problems with loading it
  into PADS, please work with me to resolve them - I envision that I should be
  able to tweak my PADS netlist generator program and/or the inputs to it until
  we get a netlist which loads perfectly smoothly.

* My vision for "netlist loading perfectly smoothly" is that after loading the
  netlist for the FCDEV3B board, PADS should recognize those components which
  have not changed from the GTA02-MB-A6 board as being completely unchanged and
  therefore not try to move them or disturb any of their trace/via/etc
  connections, while showing the newly added components as needing to be placed.
  As for net connections, where there is no change in connectivity from
  GTA02-MB-A6, it should recognize that nothing changed there (even though the
  names of the connecting nets will naturally be different) and leave those
  traces/vias/etc intact; for new or changed connections it should show rats
  needing to be routed.

* Openmoko's modem block resides on the side of their GTA02 board which they
  designated as the bottom; that side should now be reassigned to be the top,
  i.e., the board should be flipped over.  All newly added components should be
  placed on the same side as the modem core (the new top, the old bottom) so
  that the finished board will have all of its components on one side (the new
  top) and none on the other side.

* The board outline should be rectangularized, i.e., changed from Openmoko's
  complex shape fitting their plastics to simple rectangular.  Right angle
  connectors J305 (power input) and J308 (antenna SMA) must be placed along
  edges of the new rectangular outline.

* The metal shieldcan footprint SH1 should be retained exactly as it is, without
  any changes to its size or shape.  (The GND connection to this SH1 footprint
  is included in the new netlist.)  All components inside SH1 that aren't being
  removed (see below) should stay exactly where they are.  All newly added
  components (those new to FCDEV3B and not originating from GTA02-MB-A6) should
  be placed somewhere on the rectangularized board outside of SH1.

* Openmoko's GTA02 board includes microphone and speaker circuits, but they are
  not reused in the present board design.  Instead the microphone and
  loudspeaker circuits included in the present design are "new" from the
  perspective of PCB design, i.e., they don't come from GTA02-MB-A6 - they are
  based on Leonardo schematics instead.  Openmoko's audio circuits could not be
  reused because they route all analog audio signals through an external chip
  that is part of Openmoko's application processor subsystem which won't be a
  part of our FreeCalypso GSM development board.

* The specific microphone part that appears on the GTA02 PCB is no longer
  obtainable.  The present design uses a different microphone part that is
  readily available from Digi-Key, however, the new microphone part has a
  different PCB land pattern.  Therefore, the old microphone land pattern from
  GTA02-MB-A6 must not be reused.

* For the loudspeaker circuit, instead of including an actual loudspeaker part
  directly on the PCB, my circuit design includes a 2-pin header to which this
  loudspeaker is to be connected.  This way the choice of specific loudspeaker
  type does not have to be made upfront.  Some free space should be left on the
  board close to this connector (J312) so that a loudspeaker can be placed there
  and secured with double-sticky tape or similar means.

* Pay close attention to reference designators R101 and R102.  R101 and R102 in
  the present FCDEV3B netlist have absolutely nothing to do with Openmoko's
  R101 and R102.  No conflict should occur if all GTA02-MB-A6 components that
  fall outside of SH1 are removed prior to loading the new netlist, but
  otherwise beware.

* Unpopulated resistor footprints at reference designators R401, R402 and R403
  appear on Openmoko's board in the modem section, but do not appear in the
  netlist of the present design.  They should be removed from the board.  (One
  may reasonably argue that leaving these unpopulated resistor footprints costs
  nothing and does no harm, but they are so unquestionably wrong that I could
  not bring myself to work them into my design sources from which the board
  netlist is compiled.)

* The 5 components at reference designators Q1000, Q1001, R1012, R1018, and
  R1021 also appear on Openmoko's board, but not in the present board design.
  These components comprise Openmoko's circuit for controlling Calypso modem
  power and reset from their application processor; that circuit is not
  applicable to the present FreeCalypso GSM development board and hence needs
  to be removed.  This removal will lead to R208 remaining as the only component
  in that section of the board; that resistor can be moved as makes sense given
  the new netlist for the power-on and reset circuits in question.

* 0R jumper-resistors at reference designators R1003 and R1004 in Openmoko's
  original design need to be removed and replaced with solid power traces.
  Note the two already existing separate traces emanating from C214 (former
  C1009) and going toward R1003 and R1004 - simply extend these two traces to
  reach the other ends of the removed R1003 and R1004 footprints.

* The existing PCB layout from Openmoko includes a trace in the memory bus
  section that runs from U301 (former U2000) ball F9 (2nd flash bank chip
  select) to Calypso (U201, former U1001) ball C11 (nCS4).  If possible, I
  would like to have this signal go to Calypso ball C1 (nCS2) instead, for
  memory map consistency with our future quadband designs.  The current netlist
  has this signal connected to nCS2 (ball C1).  However, if moving this signal
  proves to be too difficult (too disruptive to the layout), it can be left
  where it is, and I will change the FCDEV3B netlist accordingly.

* The 32.768 kHz crystal at reference designator X201 (part MS2V-T1S) physically
  has 3 pads in its PCB footprint: two electrodes and a case ground.  The
  current netlist has it as a 3-pin component.  However, Openmoko's schematics
  show it as a 4-pin component with electrodes on pins 1 and 4 and ground on
  pins 2 and 3.  I readily admit to not understanding what's going on here.
  The PADS person will need to work with me to figure out what is happening in
  terms of how PADS sees this component, and I'll make the new netlist match
  whatever will make PADS happy and keep that part of the layout unchanged -
  it works just fine on the GTA02 board and does not need any changes.
