Kobo: Download the latest version of XCSoar and install the software on the Kobo, 

In XC Soar go to System and enable USB-OTG. Reboot the Kobo, run XCSoar in Flight mode, go to Config / Devices. Select device A: and edit the settings as follows:
Port ttyACM0
Baud rate 4800
Bulk Baud rate Default
Driver LXNAV
Passtrough device Off
Sync. from device Off

Sync. to device Off

You will have to this only once in XCSoar.

 

XC Tracer / XC Tracer II: Download and install the newest firmware. After the installation start the Vario just once in flight mode, and after this make the following changes to the config file:

stringToSend=LXWP0 
forwardGPSSentences=yes
sendDataOver=USB (sendDataOver=BOTH is also possible)
powerUSB=ON (only for XC Tracer II)
Please don't forget to save these changes!
 
Before Take Off: Connect Kobo and XC Tracer / XC Tracer II with the USG OTG Splitter Cable.
Switch on XC Tracer / XC Tracer II and the Kobo.
Only now connect the powerbank with the USB cable. (Otherwise XC Tracer / XC Tracer II will start in USB MSD mode).
The connection between the Kobo und XC Tracer will be made automatically.
 
This was tested with Kobo Glo HD and a Kobo Mini; but Kobo Glo, Kobo Touch und Kobo Touch 2.0 should be compatible too.