feat(endpoint): add select endpoint method

src/types/usb_device.rs

@@ -71,6 +71,26 @@ impl<const L: usize> UsbDevice<L> {
             dpram_already_used: 0,
         }
     }
+    pub fn select_endpoint(
+        &mut self,
+        cs: CriticalSection<'_>,
+        endpoint_index: usize,
+    ) -> Result<(), UsbError> {
+        let usb = self.usb.borrow(cs);
+        let endpoint_index = endpoint_index as u8;
+
+        if endpoint_index > 6 {
+            return Err(UsbError::InvalidEndpoint);
+        }
+
+        usb.uenum.write(|w| w.bits(endpoint_index));
+
+        if usb.uenum.read().bits() != endpoint_index {
+            return Err(UsbError::InvalidEndpoint);
+        }
+
+        Ok(())
+    }
 }
 
 impl<const L: usize> UsbBus for UsbDevice<L> {