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.