XO 1.75 A1 ECOs


Jump to: navigation, search
  This page is monitored by the OLPC team.

These are recommended engineering change orders (ECOs) to the A1 prototype of the XO-1.75 laptop. This is NOT a list of changes from A1 to A2, that is located elsewhere.


Power Sequence

These correct some unwise component selections.

Marked PWR SEQ on tags. Done to all boards.

  • PR89 <- 10K
  • PC55 <- DNP
  • PR66 <- 10K

SOC Reset

This adds a pullup to the SOC_RESET# line, needed due to a +1.8V input on the SOC driven by a +3.3V EC.

Marked as SYSRESET on tags. Done to all boards.

  • Add a 10K pullup to SOC_RESET#


A schottky diode was provided to isolate the +1.8V SPI Flash power from the rest of the motherboard, allowing incircuit programming. The voltage drop introduced by this diode (D6) was unacceptable.

Marked as SPI D6 on tags. Done to all boards.

  • R87 <- 0, which has the effect of shorting D6

USB Power

This transfers control of the USB power from the SOC to the EC.

Marked as USB on tags. Done to all boards but one of Marvell's.

  • TP199 to PQ26.2 (long blue wire)
  • PR60 <- DNP (near PQ26 on the bottom side of the PCB)

USB Role

This sets the default mode of the OTG USB interface to "master".

Marked as USBID or TP39 on tags.

  • Short TP39 to GND (the closest end of C??, the larger of the two capacitors right next to it)


This corrects a default pullup on the WLAN SDIO bus.

Marked as WLAN on tags.

  • R251 <- DNP
  • R250 <- 10K


This cleans up the camera clock signal.

Marked as CAMERA on tags.

  • L20 <- 0 ohms
  • R94 <- 22 ohms


This converts the RTC to use +3.3V instead of +1.8V, as Quanta stuffed the wrong part onto the motherboard.

Marked as RTC2 on tags. If you have a tag marked RTC, seek professional help (the ECO is missing the last two steps).

  • Move R29 to R28 (DNP -> R29, 0 -> R28, top side near LCD connector)
  • Move R99 to R98 (DNP -> R99, 2.2K -> R98, top side near D6)
  • Move R109 to R108 (DNP -> R109, 2.2K -> R108, top side near D6)
  • Move R124 to R100 (DNP -> R124, 0 -> R100, top side underneath SOC)
  • Move R125 to R106 (DNP -> R125, 0 -> R106, top side underneath SOC)

The top side of the PCB is the one closest the LCD. The Armada 610 and most components are mounted on the bottom side.


This corrects a missing pullup on the codec reset line, and a layout mistake.

Marked as AUDIO on tags.

  • R36 <- 10K (top side, underneath the codec)
  • switch pins on microphone plug (easier than modifying the PCB). After this modification, the microphone wire closest to the edge of the laptop (when the plug is seated) should be black.

USB Switch

This ECO has been withdrawn. DO NOT PERFORM THIS ECO!

There has been confusion over the polarity of the USB hub power switch enable pin. It is programmable, but not using the particular package that we are using.

Marked as USB2 on tags.

To turn on power switch whenever the USB hub is powered:

  • Remove Q3 (top side of the MB, underneath the WLAN)

To allow the USB hub to retain control of the power switch:

  • Remove Q3
  • Short the Q3 pins labelled I and O together

Fixing Display Color

This corrects the purple hue to the display, due to a wiring problem.

Marked as WHITE on tags.

  • Remove RP8 and RP9 ("bottom" side, near the DCON)
  • Wire RP8.7 to RP8.8
  • Wire RP8.5 to RP8.6
  • Wire RP8.3 to RP8.2
  • Wire RP8.1 to RP9.8
  • Wire RP9.7 to RP9.6
  • Wire RP9.5 to RP9.4
  • Wire RP9.3 to RP9.2
  • Wire RP9.1 to RP10.8
Personal tools
  • Log in
  • Login with OpenID
About OLPC
About the laptop
About the tablet
OLPC wiki