I took a little bit research for the QI standard. I found a nice document from freescale which describes some procedures for charging
http://cache.freescale.com/files/training/doc/dwf/DWF13_APF_IND_T0804.pdf
Screenshots on Windows 8.x Tablets
There is a small trick to do screenshots like on android devices. Press and hold the Windows button and while holding hit the Volume- button at the same time. Windows will save the screenshot JPG-file to the user/picture/screenshot folder.
Lenovo Miix 2-8 and Thinkpad 8 Bluetooth problems
for those who have the same problems like me while connecting a bluetooth keyboard and a bluetooth mouse at the same time and figuring out lags on the mouse here is a fix for this.
go to your device manager. under network adapters you will find a „broadcom 802.11abgn wireless sdio“ adapter.
at the setting in this adapter go to the rider advanced in the list choose „bluetooth collaboration“. further in the pull down menu go to disabled.
voila now the keyboard and the mouse work like a charm without lags and hangs…
Lenovo Miix 2-8 and internal devices working
For all who are waiting for results: i got the Huawei E3331 modem working right now. I am still at the internal 3.3V sensor port with the power source. So what did the hack? I ordered a new step-up regulator to power the device. the new one is called U3V12F5 and has a high power transistor on board. With this there is enough current to power high consumption usb stick without any problems. Measurements are about 12x6x3mm and with this it is possible to hide everything under the backcover including the Huawei modem. The Lenovo is powering up without any problems after this there is the usb modem found by windows and you can connect to the service provider without any problems. I made a test to surf around 10 minutes only with the modem activated and everything getting really smooth. So tomorrow there should be a new device arriving here. I will make some hardware tests and if all is good i will do another disassemble/teardown video from this.
Additionally I plan to make a video coverage of the Lenovo miix 2-8 with working modem too but this will take some days. stay tuned.
If there is someone out there who is interested in my miix maybe with the wires still connected to get usb devices working internal please feel free to contact me. For those who dont want wires I can dismantle everything too to bring it back to stock device.
Teaser
Here is a teaser but dont get disappointed i will present something really new…
Back @ Lenovo Miix… 5V source
After the last tests i realized that the DC-DC voltage regulator does not provide enough current for the Huawei E3331 USB modem. So today i decided to buy another voltage regulator which provides an output around 600mA @ 5V when there is an input with only 3.3V. I still hope that the sensor board will not switch off when the current rises the max. In this case i would have to go with the optional mod of the USB jack to get the whole device into OTG mode where i have several sources around on the board. I still did not get it managed to find out which transistor makes the source of 5V for the USB OTG, yet. But on the lower side of the board there are 3 of them around next to the usb board. I think the USB controller manages the voltage source and switch with the transistors through the different voltages. Hey trust me all these soldering points and modules are really really tiny on this mainboard. Only with this it is possible to build such slim and small devices but for reverse engineering and your eyes it is horror.
To go on I decided to buy a new tablet because my Miix is the last few weeks in this testing condition with cables around. But you will see soon one of the most coolest and high end devices on the market. But you can trust me it will be nothing from the „fruity company“.
Current and voltage testing at the lenovo setup
First i have to say this lenovo is eating my time a lot…
today my friend Jochen and me tested a little bit around to find out where the cut offs for the power of the internal USB port came from. My thoughts are at the input currents for the modem, the step-up controller or the output current from the 3.3V sensor connector.
We also tested with capacitors in the power lines to prevent peaks in the voltage and current lines.
So far we measured that the sensor port has peaks around 550mA when the modem is connected and right after these peaks the modem resets itself and restarts.
So the used current is really important to get a result. This will take some more time to measure where the problem persists at the moment. I will go for this soon.
Even if I did not get it managed I have a „plan b“ to realize the 3G option. At this time I am going much better with the version taking the power from the 3.3V source like I had actually done.
There will be soon a video online with some tests of the internal and OTG ports and the new Huawei E3331 Modem.
stay tuned it will take more than 2 hours to upload…
Lenovo Miix 2.8 and the power source
More research here…
Earlier i posted about the 5V source next to the micro USB port. Today i found out that the 5V source is active as soon the OTG adapter is connected even if the Lenovo is powered of. So if connected to the OTG cable the Huawei E3331 is still active even if the Lenovo is powered off. Additional the 5V Pins I figured out on the Motherboard are powered toghether with the OTG source with 5 Volts. There is so far no external power source connected. This is weird.
The internal 3.3V source switches off when the lenovo is shut down. So to prevent the modem sucking off the battery i have two options.
Buying a step up converter that makes out of the 3.3v from the sensor connector a 5V source. Second option is to connect a small relay or IC from the sensor source to switch a permanent 5V source from the OTG USB source. Research going on but the options increase in further research.