#include <inttypes.h>
#include <stdlib.h>
#include "stm32f1xx_ll_utils.h"

/**
* @brief  USBD_FS_SerialStrDescriptor
*         return the serial number string descriptor
* @param  speed : current device speed
* @param  length : pointer to data length variable
* @retval pointer to descriptor buffer
*/
uint8_t *  USBD_FS_SerialStrDescriptor( USBD_SpeedTypeDef speed , uint16_t *length)
{
  char buff[25];
  sprintf(buff, "%08"PRIX32"%08"PRIX32"%08"PRIX32,
          LL_GetUID_Word0(),
          LL_GetUID_Word1(),
          LL_GetUID_Word2()
  );

  USBD_GetString ((uint8_t *) &buff[0], USBD_StrDesc, length);
  return USBD_StrDesc;
}