v0.9 errata

[kekiefer]

This issue will stay updated for any hardware bugs found in development of v0.9 board until v1.0 hardware is ready. If you think you've found a bug in the v0.9 hardware, please open a separate issue for discussion, and this document will be updated once that discussion is resolved.

• Problem: 1.8v-capable SDHC (UHS-I and newer) cards won't work in Linux [1.8v-capable SDHC (UHS-I and newer) cards won't work in Linux #2]
  Root cause: microsd SD2 powered by NVCC_SD2, but needs a constant 3.3V
  Workaround (software): add device tree property no-1-8-v
  Proposed v1.0 solution: supply microsd SD2 VDD with VDD_3V3

• Problem: voltage sag on initial power causes pmic to shut down [voltage sag on initial power causes pmic to shut down #3]
  Root cause: excessive inrush current on VDD_3V3 due to aggressive decoupling for PCIe
  Workaround (hardware): don't stuff C125-127. Change reflected in released v0.9 BOM.
  Proposed v1.0 solution: add load switch with inrush-limiting for PCIe 3.3V rail

• Problem: Type-C port will not take host role [Type-C port will not take host role #4]
  Root cause: can't communicate with U9 (swapped sda/scl pins)
  Workaround (hardware): cut and jump to pull up resistors R19/R20 (see linked issue)
  Proposed v1.0 solution: fix scl/sda pin swap

• Problem: Advise in BQ27426 notes is not followed [U12 pin BIN shorts to Vss against advisement of datasheet #5]
  Root cause: U12 pin BIN shorts to Vss when battery is used
  Workaround (hardware): cut and jump R51 to configure as BIN pulldown to GND (see linked issue)
  Proposed v1.0 solution: don't include Q1 and configure R51 as pulldown

• Problem: Battery over discharge protection circuit does not work [Battery over discharge protection circuit does not work #6]
  Root cause: disabling discharge with IO on charger did not work as intended
  Workaround: use a pack with integrated protection circuits.
  Proposed v1.0 solution: add a FET to properly disconnect battery on fault

• Problem: Some out-of-spec but common mPCIE cards do not fit [Certain high-power mPCIE wireless cards will not fit #7]
  Root cause: cards interfere with components on the board
  Workaround (hardware): replace mPCIE connector with 2041262-1
  Proposed v1.0 solution: update BoM