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”.