#define  SD_CS_PIN    GPIO_Pin_4  /*    */

#define  SD_CS_LOW    GPIOA->BRR  = (uint16_t)SD_CS_PIN;
#define  SD_CS_HIGH   GPIOA->BSRR = (uint16_t)SD_CS_PIN;


inline __attribute__((__always_inline__)) uint16_t spi_xfer (uint16_t val)
{
  SPI1->DR = val;
  while ((SPI1->SR & SPI_I2S_FLAG_TXE ) == 0)   { /*  wait  */  };
  while ((SPI1->SR & SPI_I2S_FLAG_BSY)  != 0)   { /*  wait  */  };
  return SPI1->DR;

} /* --- spi_transfer --- */


/* ---------------------------- */
/*   Receive multiple byte      */
/* ---------------------------- */
static  void rcvr_spi_multi
(
  uint8_t *buff,      /* Pointer to data buffer */
  uint16_t numbytes   /* Number of bytes to receive (even number) */
)
{
  uint16_t ii, dummy;

  SD_CS_LOW;
  dummy = 0;
  ii = 0;
  do          /* Receive data block into buffer */
  {
    *(buff+ii) = spi_xfer(dummy);
    ii++;
  } while (numbytes > 0);
  SD_CS_HIGH;

} /* --- rcvr_spi_multi --- */


/* ---------------------------- */
/*   Send multiple byte         */
/* ---------------------------- */

static  void xmit_spi_multi
(
  uint8_t *buff,      /* Pointer to data buffer */
  uint16_t numbytes   /* Number of bytes to receive (even number) */
)
{
  uint16_t ii;

  SD_CS_LOW;
  ii = 0;
  do          /* send data block into buffer */
  {
    spi_xfer(*(buff+ii));
    ii++;
  } while (numbytes > 0);
  SD_CS_HIGH;

} /* --- xmit_spi_multi --- */