XO1.75 A1 A2 Changes

These are the changes planned for the XO-1.75 A2 prototype, from the A1 prototypes.

A1 Fixes

These changes fix problems in the A1 prototypes:

Power Sequence

• 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.

• 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.

• Remove D6 (shorting it)

USB Power

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

• 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".

• 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.

• R251 <- DNP
• R250 <- 10K

Camera

This cleans up the camera clock signal.

• L20 <- 0 ohms
• R94 <- 22 ohms

Audio

This corrects a missing pullup on the codec reset line.

• R36 <- 10K (top side, underneath the codec)
• switch pins on microphone plug

Camera Conn.

Move the camera connector back to the correct location

Debug Conn.

• Eliminate the Marvell JTAG debug connector.
• Replace the JTAG debug connector with one easier to mount in the field ?

Fix DCON green wiring

• GFDDAT0~6 pins on DCON need to be wired as with CL1B, with the DCON GFDDAT0 input connected to GND.

Planned Feature Changes

Audio Codec

• Change to ALC5631Q
• Wire input circuit to route internal mic. through the audio input jack.
• Add Jack Sense for the headphone jack.

Internal Storage

• Change the Micro SD to external SD.
• Add a jumper to indicate whether OFW should try to boot from internal SD or eMMC.

Embedded Controller

Change to EC IO3731

Restore Gamepad

• Modify the game buttons from 4 buttons to 8 buttons.

Battery Charger

• Change battery charger IC as the one used in XO-1/1.5 is being EOL'd. Modify the related circuit.