USB pins

The USBHS peripheral features a number of dedicated pins which can be grouped into two categories: signal and power.

Signal pins connect to the USB device and consist of the D+ and D- pins. These are dedicated pins and not available as standard GPIO pins. The data line does not need serial resistors. TXRTUNE connects to a tuning resistor on the PCB. The USBHS does not have an ID pin. The USBHS peripheral is implemented according to the USB Specification v2.0, 5V Short Circuit Withstand ECN Requirement Change, meaning these pins are not 5 V tolerant.

See Reference circuitry for the reference circuit diagram.

The signal pins are operational when the following are true:

The device is powered
VBUS is in the valid voltage range
USBHS is enabled by the software driver

Note: The D+ and D- pins are impedance controlled signals and must be routed on the PCB according to the USB standard. See the development kit user guide for a routing example.

TXRTUNE resistor

An external resistor with 200 Ω resistance and 1% tolerance must be connected from the TXRTUNE pin to the VSS pin to calibrate a 45 Ω source impedance for the D+ and D- pins. Using a constant current output from the TXRTUNE pin and measuring the voltage over the external resistor, the nominal voltage over the resistor will be 400 mV.

VBUS detection

The VBUS pin has a voltage detector for both rising and falling voltage. This means it will detect the USB cable being connected and disconnected. The voltage detector generates events that are picked up by the USBHS software driver, which can be used as wakeup-sources for the device.

For pin assignments, see Pin assignments.