MQX Software Solutions中的主题 Low level SD card access

Low level SD card access

MPotts — Sat, 23 Jul 2011 03:33:20 GMT

I am trying to implement low level access (read and write single sectors) from/to an SD card. I have studied the SPI and SD Card sections in the I/O Drivers Guide and the sdcard sample and come up with the following code (including scard.c and sdcard_spi.c plus headers):

MCF5XXX_QSPI_INIT_STRUCT _qspi0_init = {
   0,                            /* SPI channel                     */
   MCF5XXX_QSPI_QDR_QSPI_CS0,    /* Chip Select 0                   */
   SPI_DEVICE_MASTER_MODE,       /* Transfer mode                   */
   BSP_QSPI_BAUDRATE,            /* SPI Baud rate register value    */
   BSP_SYSTEM_CLOCK/2,           /* Clock Speed                     */
   SPI_CLK_POL_PHA_MODE0,        /* SPI clock phase                 */
   BSP_QSPI_RX_BUFFER_SIZE,      /* Rx Buffer Size (interrupt only) */
   BSP_QSPI_TX_BUFFER_SIZE       /* Tx Buffer Size (interrupt only) */
};

SDCARD_INIT_STRUCT _sdcard0_init = {
    _io_sdcard_spi_init,
    _io_sdcard_spi_read_block,
    _io_sdcard_spi_write_block,
    MCF5XXX_QSPI_QDR_QSPI_CS0
};

_mcf5xxx_qspi_polled_install("spi0:", &_qspi0_init);
spifd = fopen("spi0:", SPI_FLAG_HALF_DUPLEX);
rc = _io_sdcard_install("sdcard:", &_sdcard0_init, spifd);
rc = _io_sdcard_spi_init(spifd));
rc = _io_sdcard_open(spifd, "", "");
rc = _io_sdcard_write_blocks(spifd, buffer, n);
rc = _io_sdcard_read_blocks(spifd, buffer, n);

On execution the code hangs in _io_sdcard_spi_init(). Any suggestions as to possible causes appreciated.

Mark

Re: Low level SD card access

PetrM — Mon, 01 Aug 2011 15:01:33 GMT

Hello,

you should access sdcard through its posix API:

_mcf5xxx_qspi_polled_install("spi0:", &_qspi0_init);

spifd = fopen("spi0:", SPI_FLAG_HALF_DUPLEX);
rc = _io_sdcard_install("sdcard:", &_sdcard0_init, spifd);

sdcardfd = fopen ("sdcard:", NULL); // this calls _io_sdcard_spi_init() internally

  fwrite (buffer, 1, n, sdcardfd);
  fread (buffer, 1, n, sdcardfd);

Regards,

PetrM

Re: Low level SD card access

MPotts — Wed, 03 Aug 2011 07:02:41 GMT

Hi PetrM,

Thanks, this works a lot better. It now fails to open the SD card if it no card is present present but succeeds if there is!

However fwrite() and fread() both return -1 which I assume indicates an error. How do I determine the precise error?

Mark

Re: Low level SD card access

MPotts — Thu, 04 Aug 2011 04:51:33 GMT

Solved the fwread/fwrite problem. The counts are in sectors (512 bytes) not bytes. All now working well.

Mark