To detect when USB for the interface MCU is connected, there is a circuit sensing the VBUS of USB connector J2.
When the USB cable is connected, the VDD is propagated to the USB_DETECT signal.
Figure 1. USB detect
To detect when USB for the interface MCU is connected, there is a circuit sensing the VBUS of USB connector J2.
When the USB cable is connected, the VDD is propagated to the USB_DETECT signal.