If I read the TLE5010 datasheet correctly, that GEN pin is probably the external 4 MHz chip clock input, see chapter 7 in the datasheet.
[GEN = generator?]
Hi Ignacio,
No idea...but it will help if you post an updated connection diagram and share your Arduino code (see the Forum Rule on top of this page).
BTW: is your project related to Teensy 2.0 + MMjoy2 firmware = Joystick Controller?