I want to change my RCD 310 (VW Passat CC 2011) by Android Device. Everything is working except steering wheel controls. I know that in some number of cars steering wheel control is working with rheostat. So there are two wires, say mass-wire (usually minus) and control-wire. The rheostat is placed into the wheel and these two wires connected to the device. So the device measure the resistance in this electrical circuit and make a decision about which button is pressed or nothing. But in the Internet I can't find whether RCD 310 have rheostat-technology or may be some other tech. By this PINs (see the picture) I can't determine it and even it's true I can't determine where is control-wire. Please help!)
Not sure what references you have regarding the "rheostat" device..
On these cars the steering wheel is connected to the Infotainment databus (a CANbus) and the stereo is also connected to the Infotainment CANbus on pins 9/10 (CAN high/low).
You'll need to check if you have connected the android head unit's CANbus connection, or if even it is compatible.
Update: The unit is compatible and even refers to "steering wheel control". This is connected to the car via the quad lock connector, pins 9-10. Very common across the VW/Audi range. So I am quite sure on this. The steering wheel sends messages on the databus with a certain address and the relevant button press data.
You need to trace the wires from those pins and make sure you have the wires connected up. Outside of that, engage the product support because it should 'just work'