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This is a page to keep track of our PCB revisions, document design changes, and receive feedback.

Revision 1  

PCB design decisions

  • All components on top of board except clik-mate connectors and debug LEDs (also TVS diode and 3 decoupling caps)
  • Board dimension target is 5 cm x 5 cm (not of vital importance)
  • Mounting holes (M4) on each corner
  • Mezzanine connector will be close to the center of the board
  • 2-Layer PCB with 1oz copper

Retrospective

  • The board worked!
  • Kevin's regulator design has not been tested yet, but Titus's regulator design worked well and had minimal ripple and relatively high efficiency under light loads (87% @ 10mA).
  • The 1.25mm Clik-Mates were impossible to crimp and we'll definitely need a real crimper for the 1.50mm Clik-Mates that we plan on using.
  • Most of our boards require powering the carrier board directly and the only purpose of the 12v rail is to power the regulator, so we can just remove the 12v connector from the controller board.
  • The crystals are huge. They need to be replaced.
  • The mounting holes are excessively large.
  • The QFN chip is actually solderable by hand (Kevin Chen (Unlicensed))
  • We definitely need a stencil to do proper reflow.
  • The blue LEDs are way too bright.
  • We haven't tested the crystals yet.
  • We haven't the mezzanine yet.

Revision 2  

Design Changes

  • Remove extra regulator circuit (Kevin's), source smaller crystals, make all resistors and LEDs 0603
  • Fix trace lengths for crystals
  • Reverse voltage protection?
  • Fix all footprints to match the Hardware Style Guide
  • Replace board info silkscreen as directed in the Hardware Style Guide (TBD)
  • Connector changes:
    • Combine SWD and UART into a 6 pin 1.5mm clikmate connector
    • Replace 12V connector with test points
    • Replace mezzanine connector with 0.8mm pitch equivalent to increase lifespan and verify mating height
    • Change all connector part numbers to vertical connectors
    • put male side of mezzanine on controller board
    • Add guide holes for mezzanine footprint
    • Switch signal connectors to 1.5mm Clik-Mate and power connector to something else
    • Silkscreen pinout for connectors
  • Combine SWD and UART headers (we may be able to hack the programmers to also be UART to USB adapters) or replace them with prototyping headers
  • Reduce induced ripple on 12V rail
  • Improve ripple behavior on 3.3V rail
  • Calibrate regulator to 3.3V (currently at 3.36V)
  • Get stencils
  • Lower blue LED brightness (spec an LED ), raise green LED brightness


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