Status with examples/device/cdc_msc:
- make BOARD=stm32f723disco => OK
- make BOARD=stm32f723disco PORT=1 => No Reaction
- make BOARD=stm32f746disco => OK
- make BOARD=stm32f746disco PORT=1 => Hangs during enumeration
- make BOARD=stm32f769disco => Hangs during enumeration