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Pocket P.C. Rev 2.1 Change Log
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Pocket P.C. Rev 2.1 Change Log
(Lessons from D.V.T.)


Problem: Port0 USB Differentials are swapped

Solution: Unswap them in the schematic

Temp Solution: Use wires to swap the differentials where L9 should be.

Problem: PORT0 USB Differentials are swapped

Solution: Swap Differentials

Temp Solution: Criss-Cross L9 with 0.01mm wire.

Problem: DRAM Voltage 2 too High 1.5V

Solution: Change DCSET5 resistor to floating to set to 1.24V

R108 is NC


Problem: DRAM Voltage 1 too High 2.3V

R102 is 0R and R101 is NC

Solution: Move VCC-PG voltage rail from ELD01 to DLDO4

R102 is NC and R101 is 0R


Problem: IPSOUT net is not powered.

Solution: Connect PS voltage rail to IPSOUT

Temp Solution: Connect a wire from TP26 to C67

Temp Solution: Use 30GA  wire from TP26 to C67

5.) SD Card Data nets are swapped


Change Antenna type.

Problem: Manufacturer sourced the wrong LPDDR3. They purchased ATL3A1632-H12A by ARTMEM. The BOM calls for AWL3A1632-12D2L32CS by mTech.

Solution: Make sure they purchase the right component before the next Assembly.

Problem: JP1 is missing a copper trace connecting the middle and right side of the jumper.

Solution: Add copper in layout.

Temp Solution: Jump/connect two pads with solder.

Problem: Even though the AA701/AA702 antenna has the same form factor, the layouts are different for high and low frequency bands.

Solution: Use the C412D5 antenna as it is better suited for the edge of the board and the same layout will work on all frequency bands.

Suggestion: Need to move down U8 and relocate J4.

Problem: Card detect is not present in the schematic and PF6 is used for CRYPTO-RST instead of being used for card detect.

Solution: Add Card Detect Pin to schematic and connect to PF6. Move CRYPTO-RST to PH11. Add 10K pull-up to Card Detect net on microSD schematic page.

Problem: SD-DAT0 and SD-DAT2 are swapped.

Solution: Swap these signals in schematic on U15G component.

Problem: U37 has extraneous pin labels.

Solution: Rename pin 2,4,5,6,7,11 to say NC. Keep connected to the ground.

Problem: We used GPIO on TPS65988 and these cannot be used without a Kernel Driver that must be developed.

Solution: Move GPIO from U26A to A64 SoC. (Wait for confirmation.)


Problem: D.V.T. circuit boards do not handle 20V from USB-C

Solution: Double check all high-voltage capacitors in inventory and label the appropriate voltages in the schematic and update BOM to reflect voltages. Ex. C219 (22uF), C220 (1uF), C221 (22uF), C222 (1uF), C27 (10uF), C26 (0.1uF)

Test Results: D.V.T. Board #2 failed short on C220 and C221 capacitors.

Problem: TVS4 interferes with Top Cover Plastics

Solution: Move TVS4 away from the top cover plastic rib.

Problem: L11 burnt up after the LCD was connected.

Solution: Connect OVP to the positive terminal of the output capacitor.

Problem: U40 (keyboard/system controller) does not know when device is powered-on.

Solution: Add a 10K 0402 pull-up to PB4 of U40

Remove the ground plane beneath L9.

Add a 0R resistor to the 3.1V net connected to J2 as it is not used in our final display.

Extraneous Schematic Changes


  1. Delete VCC-Sensor and VCC-CTP. Make sure they are unused in the schematic.


  1. GPIO0-LDO, GPIO1-LDO Test Points
  2. DC1-SW Test Point
  3. U9 OE and SEL Test Points
  4. U11 VCC_IN and VIN Test Points


  1. C28 should be 75pF not 75uf.
  2. R135 DIN_P pull-up on U40 should connect to VCC-MCU-3V3 to be consistent with the rest of the power domain.
  3. R68 and R69 should be 1K
  4. R100 should add the “R” so it says 240R-1% to match R123 and R124. These are the same part values.
  5. Change J1 to ANT3
  6. Add Testpoints on LCD-SDA and LCD-SCK

BOM Errors

  1. L9 has the wrong part number.


  1. Test PORT2 audio circuitry. -- Tested OK

Schematic Part Number Changes

  1. L9 should be “SDCW2012-2-900TF”
  2. L11 should be “WPN3012HS100MTY01”
  3. U16, U25, U24, U17 should be “TPD6S300A”
  4. R68, R69, R133 should list the part value. It is missing.

Board Silkscreen Changes

  1. U24 pin one indicator should move because it overlaps with U24 silk.
  2. Remove A1, A12, B1, B12 silk from J5,J6,J9,J8 component footprint  

Capacitor Changes

  1. C119,C152,C184,C186 from 0402 to 0603
  2. capitalize the f in uF on C61, C62, C67 in the schematic
  3. C78 from 0201 to 0603
  4. C103 from “1U” to “NC/1uF”
  5. Capitalize the f in uF on C18 and C19

Post-Schematic Update (12/28/2020)

  1. R39 should be 0R01 not 0R
  2. R200 should not have the “may remove after testing note”
  3. U10 LCD-SDA and LCD-SCK should have test points
  4. R26 should have tolerance marking
  5. C27 and C26 should show voltage rating on the schematic.
  6. R61 has a lower case r0402
  7. R20 should just be 10K
  8. C20 should be DNP
  9. R12 value text overlaps with package text
  10. R149 should be DNP
  11. Add part number for ANT1 to the schematic
  12. Remove this text from the schematic on page 6 “FCC/CE Pre-certified external antennas are listed in the C.H.I.P. Pro User Manual”
  13. U31 INTN should connect to A64 SoC. Add a 10K pull-up and connect to PL7 on U15H

SWITCHOVER_SEL (Keep pull-down on U26A)

U15E -- PE0


U15E -- PE1


U15E -- PE2

LCD-HPD (Keep Testpoint on LCD-HPD)

U15E -- PE3


U15E -- PE4


U15E -- PE5


U15E -- PE6


U15E -- PE7

PG12 is incorrect.

Schematic/BOM/Layout Update (01/04/2020)

VBUS Ferrite Bead (J8 and J9)

FBMJ2125HM210NT Taiyo Yuden | Filters | DigiKey

  1. Add a ferrite bead (FB3) between TVS4 and PORT1_VBUS label.
  2. Add a ferrite bead between (FB4) TVS3 and PORT0_VBUS label.