I almost finished the board.h it will be ready for tomorrow so we can start to port our project to the swarm board.
I also determine that the driver I used for the MPU wasn’t good at all and provided some false results. There are some more drivers out there but very few proposed the Digital Motion Processor (which is doing the fusion internally) support.
I emailed invensense to have access to their developer download corner : they seem to propose some proprietary driver for the MPU9250. So I am waiting for an answer.