Enabling interrupts

Hi,

I want to enable interrupts so I can empty the FIFO only when needed (I don't want to poll for interrupts).

What is the correct sequence for this?

I don't see any code setting up reg 55, and unfortunately the document does not state the reset defaults of this register (in fact for none of the registers??) so I have no idea what the interrupt level, latch, etc is.

What is the correct sequence of calls?

Do I need to register a function with the MotionApps through inv_register_dmp_interupt_cb? I don't see why, because my OS handles the interrupt when it occurs (through ISR->IST).

The AT32 code does not have an example for this, so any pointer (to documentation or otherwise) would be much appreciated.