+\r
+ #if (!defined(NO_INTERNAL_SERIAL) && (defined(USB_SERIES_6_AVR) || defined(USB_SERIES_7_AVR))) || defined(__DOXYGEN__)\r
+ /** String descriptor index for the device's unique serial number string descriptor within the device.\r
+ * This unique serial number is used by the host to associate resources to the device (such as drivers or COM port\r
+ * number allocations) to a device regardless of the port it is plugged in to on the host. Some USB AVRs contain\r
+ * a unique serial number internally, and setting the device descriptors serial number string index to this value\r
+ * will cause it to use the internal serial number.\r
+ *\r
+ * On unsupported devices, this will evaluate to NO_DESCRIPTOR and so will force the host to create a pseduo-serial\r
+ * number for the device.\r
+ */\r
+ #define USE_INTERNAL_SERIAL 0xDC\r
+ #else\r
+ #define USE_INTERNAL_SERIAL NO_DESCRIPTOR\r
+ #endif\r