Today I finished the TP. My problem with lwIP was that after reading the buffer, the connection is closed. So I reinitialized it and it worked.
After that, I activated a debug option and I had to redo all my callback functions. For the buttons and the trimmer, as I did my own functions, I just changed chSysLock to chSysLockFromIsr. For the usb, I had to create an other thread and to wait for an event.