The SAM L21 Xplained Pro has a Micro-USB connector for use with the SAM L21 USB module labeled as TARGET USB on the kit. To be able to detect when a target USB cable is connected in self-powered mode, a GPIO is used to detect the VBUS voltage on the connector. In USB host mode VBUS voltage is provided by the kit and can thus not identify a connected device, so another GPIO is used to detect the USB ID of the device.
| SAM L21 pin | USB function | Shared functionality |
|---|---|---|
| PA14 | VBUS Detection | Crystal footprint |
| PB02 | USB ID | - |
| PA24 | USB D- | - |
| PA25 | USB D+ | - |