[Andy]

The USB hub came today and I did another speed test with the logitech unifying receiver and flash drive plugged into the hub and the hub plugged into the GSM usb connection.  The results are approximately 8% slower than without the hub.  My plan is to use the internal flash drive for dropbox, google drive, and other storage where speed isn’t as critical.  Games and other files will go on a microSD or internal memory.

 

I am quite pleased with the small size of the USB hub.  The USB connectors will be removed and the board is small enough to fit in the cutout on the board where the sim card socket would normally go.

 

USB Hub

USB Hub Design

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[Andy]

I started with the guitar pick method, but ended up getting stuck about halfway down the length of one side.  The clips on this tablet are very tight.  I ordered a set of spudger type tools on amazon and one of the thin angled plastic spudgers was able to get between the sides of the case and the plastic frame.

The resistors I used appear to be 1mm 1/16 watt.  They were scavenged from some old PATA hard drive controllers.  You may be able to fit 1.6mm ones.

The new candidate +5V location is shown in the attached image.  It shows +5V with/without USB OTG plugged in. That chip appears to be a clone of the TPS76050DBVR.

 

BTW, which tablet is that?  Are you going to try to attach to the GSM USB connection?

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[Andy]

Thanks!  I hope others are able to do the mod as well.  Using a “charger doctor” (which I don’t have a ton of faith in), my flash drive is showing 10-30mA and the unifying receiver is using too little to measure.  So I think you’re right, this seems like a negligible power draw.  It looks like the +5V regulator is right next to the battery compartment, and it’s showing voltage without the OTG cable plugged in.  I have a tiny USB hub coming Thursday, so I’m going to try to cram it all in there (hub, flash drive, unifying receiver) when it gets here.

[Andy]

The unifying receiver was swapped for a USB socket and a speed test was conducted for both the GSM USB connection and the OTG cable.  Results attached.  Next I will try to add a small USB hub so both the flash drive and unifying receiver can be stored internally.

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[Andy]

Success!  It works!  Instead of the bridges shown in my diagram I installed 33 Ohm resistors.  I believe these resistors should be 27-33 Ohm (based on Intel’s USB specification).

 

For my test I hard-wired a logitech unifying receiver.  I also plugged a flash drive into the USB OTG cable to ensure they could both operate at the same time.  The only problem I am currently having is the pad where I’m getting +5V is only active when the OTG cable is plugged in.

 

As soon as I find a better +5V source I’ll do some R/W speed tests on a flash drive.

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[Andy]

A bit of research leads me to believe that the USB connection on the GSM modem pad might be usable.

 

The x5-Z8300 product brief shows the modem connecting to a USB 2.0 interface.  http://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/atom-x5-processor-z8300-product-brief.pdf

 

The Teclast X98 Air 3G used the Fibocom H350 module, and I believe that is what the pinout on the X98 Plus’ board is setup for.  http://www.tme.eu/en/Document/3ad829449e4f7998c66f800c971a89c4/FIBOCOM_H350UM.pdf

 

The USB D+ and D- pads for the GSM module appear to be NC, but they do connect to a location a few millimeters away where some SMD resistors would likely go.  I believe we may be able to bridge those connections to enable D+ and D-.  The GND pin seems to be good.  Unfortunately the VUSB pin seems to be NC.  I’m guessing there’s a missing capacitor somewhere on the board.  Now I just need to find a convenient place to grab +5V and I’ll give this a test.

 

Diagram attached.

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[Andy]

There is a single large shield over the center area of the board.  You can see the border of it on the circuit board and the outline of it against the large black sticker.  The large black sticker has a thin brown metal sheet on the outside.  I’m guessing it’s either a heat shield or heat spreader.  Underneath the metal shield that attaches to the board are 3 silicone pads.  One of them covers the processor and 2 of them cover the 4 memory chips.  I’ll grab some more pictures later tonight.

[Andy]

I attached the images to the post, but I’m not seeing them attached.  In case they don’t show up, here they are at Imgur:  http://imgur.com/a/hbvzo

 

 

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