XO 1.75 A1 ECOs

From OLPC
Revision as of 04:51, 20 November 2010 by Wad (talk | contribs) (→‎RTC)
Jump to navigation Jump to search

These are recommended engineering change orders (ECOs) to the A1 prototype of the XO-1.75 laptop.


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#

OFW SPI Flash

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

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)

WLAN

This corrects a default pullup on the WLAN SDIO bus.

Marked as WLAN on tags.

  • R251 <- DNP
  • R250 <- 10K

Camera

This cleans up the camera clock signal.

Marked as CAMERA on tags.

  • L20 <- 0 ohms
  • R94 <- 22 ohms

RTC

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.

Audio

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

Marked as AUDIO on tags.

  • R36 <- 10K
  • 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.
Retrieved from "http://wiki.laptop.org/mediawiki/index.php?title=XO_1.75_A1_ECOs&oldid=248836"