This pin is used for identification of device role.
FX3 is compliant with the OTG Specification Revision 2.0. In OTG mode, FX3 supports both A and B device modes and supports Control, Interrupt, Bulk, and Isochronous data transfers.
OTG_ID pin can be left unconnected if FX3 is used as a USB device only.
This pin must be connected to ground if you are using FX3 as a dual role device.