Tuesday, January 26, 2016

Inside stuff - Lenovo Miix 3 830 tablet

A few months ago I bought a cheap Windows 10 tablet for having a dedicated bench instrument that I could connect the oscilloscope, multimeter, logic analyzer to.
You can see a bit of it in action in the last photo belonging to this post: http://hackcorrelation.blogspot.com/2015/10/adding-isolated-data-output-to-mastech.html

Quick review


The bad


This is by no means a powerhorse. It is faster than a Pentium 3 desktop but struggles with Chrome tabs. 2GB of RAM does not help a lot either.

Touch input is a bit spotty, sometimes taking one second to respond to a scroll request. On top of that, Windows 10 is not (yet) optimized for touch input which means a lot of the times you'll be hitting the wrong button or link.

The other annoying thing is that it cannot charge and use its USB port at the same time - I've already tried a few USB OTG hubs with different settings.

Coming out of standby takes between 2 and 5 seconds.

The screen is pretty glossy, but at least it's bright enough to use in daylight. However it lacks a luminance sensor.




YouTube and general HTML5 performance requires a lot of patience. I would suggest disabling autoplay through Magic Actions. Streaming through ChromeCast is choppy.

The speakers sound tinny and are no match for the iPad Air ones.

The good


Enough with the negative stuff, there are actually some pretty nice features.
It runs most software you would generally need in the lab: data logging, spreadsheet/document editing, compiling source code, interfacing various USB development boards. You could connect it to an OBD interface and have a portable car [tuning] computer.

The onboard HD graphics are decent enough to run previous-gen games, LFS runs at a steady 60fps, old-school games (Diablo 2) present no issue.

Using IE/Edge browser is a provides better experience, if you don't care about ads.
Regarding ads, using Chrome with AdBlock plus is a joy and you can finally watch YouTube without unskippable ads. That was the main reason I quit using my iPad Air.

While streaming through ChromeCast / EZCast is slow, using it as a second monitor through SpaceDesk is almost enjoyable.

Battery life is pretty decent, between 3 and 6 hours, possibly even more if doing light stuff.

This will be my main tablet for a while, until the Core M or X8500 units with keyboard covers reach a decent price.

The teardown


Since this part will have a lot of pictures I have to insert a page break here. ---

The unit comes easily apart with an assorted set of guitar picks. 




After I took the pictures I found out that Lenovo actually has a repair manual for the unit where the recommend using ... guitar picks.







From top left: sound jack, microUSB charge/OTG port, microSD slot, speaker.

Left side: power, volume up, volume down switches, sound card chip (under shielding can), main power regulator and charging interface for the battery.

The battery is a 3.7V 4.15Ah 15.5Wh LiPo that connects with 7 wires - I suspect 3 of them positive voltage, 3 ground and one providing temperature sensing.



Viewing the bottom left corner (from behind): wireless and Bluetooth chip under shielding, antenna connectors for WiFi and BT, connector for touchscreen interface, microphone pads.

In case of bad touch response the TPCON1 connector could be reseated, but I haven't had that kind of issues with my unit.




Removing the shielding cloth beneath the microphone pads reveals a Goodix GT9113 capacitive sensing unit. According to the linked datasheet it's able to provide both an I2C and a USB interface, with Windows 8 drivers.
While not high on English the datasheet describes in great detail how to interface the chip, including a reference design with the companion part GTM802. It's currently not available on octopart.com.






Two gratuitous shots of the mainboard backside.

For no reason other than to use that word. Gratuitous.
















The mainboard lifts out of the plastic snaps with a bit of contortion, the audio jack needs to come downward a bit so it's able to get out of the retaining round clip.

You can either bend the board a little or remove each and every connector on the mainboard.








A clearer shot of the sound card that was hiding under a metal can. Nearby you can also see the USB traces and OTG sense lines which will come in handy in case you want to perform a mod that allows charging while using OTG.


The sound chip is a Realtek ALC5640. The closest matching part number that I found was the datasheet for is ALC5634.

Now we come to the interesting part, CPU, RAM and Flash:










In the midst of all this sits a small chip AXP288 which is a PMIC designed especially for Baytrail and Cherrytrail platforms:
.

The SoC and PMIC chips have matching thermal pads on the underside of the metal can


Two more shots of the motherboard top side, for reference purposes. As usual, the photos are uploaded at full resolution whenever I believe they offer useful information.


No comments:

Post a Comment