0xFF

#define SIZE_FREE 1 // rg[] Flexible array member not supported in C++

typedef struct{
  t_USB_Header    Header;
  uint8_t          bLength;
  uint8_t          bCM;
  uint8_t          bId;
  uint8_t          prgBegin[SIZE_FREE];
}t_PT_DEVICE_SEND_DATA;