What are the hardware design recommendations for the BL653/BL654 USB interface if not used?

The BL653/BL654 provides an USB 2.0 full-speed (12 Mbps) interface which is compliant to the Universal Serial Bus Specification Revision 2.0. We recommend connecting VBUS to GND and leaving both D+ and D- data pins unconnected if developers do not need or want to implement the USB interface in their hardware designs. Please note that smartBASIC does not support USB functionality, so for software and application development you would need to either use Zephyr or the Nordic SDK.