[sciurius]

I use a OTG cable - but all of the OTG cables are made to put the power to a harddisk for plugging to a smartphone or tablet.

That is exactly what an OTG cable is intended for.
When connecting a PC to the tablet, the PC is the master and the tablet the slave.
With the OTG cable, the tablet is the master, and the other device is the slave.
There are special OTG cables (Y-cables) that allow charging and data at the same time, see e.g. https://sites.google.com/site/sonicboomw...g-diagrams