We can use the turnigy 9x/flysky th9x to learn to fly in linux.
The FrSky telemetry module has a rs232 port on the back. This port has RS232 voltage levels (~12V), which is incompatible with the AVR microcontroller inside the 9x. We need to make a level converter. We could use a maxim 232 IC to do this but in several places in internet is not recommended because it requires you to disconnect this converter while you are programming the AVR. Instead we follow the guide here : http://code.google.com/p/gruvin9x/wiki/FrskyInterfacing . With this circuit everything works fine! Also, it's compatible with er9x firmware.
To compile with frsky mods and without the templates and heli menus:
make EXT=FRSKY TEMPLATES=NO HELI=NO
Then use eepe to upload flash and eeprom