C - Initializing an SD card in SPI mode, always reads back 0xFF

I'm trying to initialize a 2 GB SanDisk SD card on a Cypress PSoC 5 using the SPI interface. I'm using the sample bit banging code from FatFs - Generic FAT File System Module. I've analyzed the interface on a logic analyzer (see

). The problem is that the data out line from the SD card is always high, I should be getting back a 0x01 from the card init command. The SD card reads fine on the PC however. The code I am using is below, what could the problem be?

I'm using an SD socket from http://ucontroller.com/documentation/SDCardDoc.html.

/*------------------------------------------------------------------------/
/  Bitbanging MMCv3/SDv1/SDv2 (in SPI mode) control module
/-------------------------------------------------------------------------/
/
/  Copyright (C) 2010, ChaN, all right reserved.
/
/ * This software is a free software and there is NO WARRANTY.
/ * No restriction on use. You can use, modify and redistribute it for
/   personal, non-profit or commercial products UNDER YOUR RESPONSIBILITY.
/ * Redistributions of source code must retain the above copyright notice.
/
/--------------------------------------------------------------------------/
 Features and Limitations:

 * Very Easy to Port
   It uses only 4-6 bit of GPIO port. No interrupt, no SPI port is used.

 * Platform Independent
   You need to modify only a few macros to control GPIO ports.

 * Low Speed
   The data transfer rate will be several times slower than hardware SPI.

 * No Media Change Detection
   Application program must re-mount the volume after media change or it
   results a hard error.

/-------------------------------------------------------------------------*/

#include <device.h>
#include "diskio.h"        /* Common include file for FatFs and disk I/O layer */


/*-------------------------------------------------------------------------*/
/* Platform dependent macros and functions needed to be modified           */
/*-------------------------------------------------------------------------*/

#include <device.h>                /* Include device specific declareation file here */

#define INIT_PORT()   /* Initialize MMC control port (CS/CLK/DI:output, DO/WP/INS:input) */
#define DLY_US(n)      CyDelayUs(n)    /* Delay n microseconds */

#define CLK_DELAY()   CyDelayUs(1)
#define CS_H()        CyPins_SetPin(ss_0)        /* Set MMC CS "high" */
#define CS_L()        CyPins_ClearPin(ss_0)      /* Set MMC CS "low" */
#define CK_H()        CyPins_SetPin(clk_0)       /* Set MMC SCLK "high" */
#define CK_L()        CyPins_ClearPin(clk_0)     /* Set MMC SCLK "low" */
#define DI_H()        CyPins_SetPin(spiout_0)    /* Set MMC DI "high" */
#define DI_L()        CyPins_ClearPin(spiout_0)  /* Set MMC DI "low" */
#define DO            CyPins_ReadPin(spiin_0)    /* Get MMC DO value (high:true, low:false) */

#define    INS        (1)            /* Card is inserted (yes:true, no:false, default:true) */
#define    WP         (0)            /* Card is write protected (yes:true, no:false, default:false) */



/*--------------------------------------------------------------------------

   Module Private Functions

---------------------------------------------------------------------------*/

/* MMC/SD command (SPI mode) */
#define CMD0      (0)        /* GO_IDLE_STATE */
#define CMD1      (1)        /* SEND_OP_COND */
#define ACMD41    (0x80+41)  /* SEND_OP_COND (SDC) */
#define CMD8      (8)        /* SEND_IF_COND */
#define CMD9      (9)        /* SEND_CSD */
#define CMD10    (10)        /* SEND_CID */
#define CMD12    (12)        /* STOP_TRANSMISSION */
#define ACMD13   (0x80+13)   /* SD_STATUS (SDC) */
#define CMD16    (16)        /* SET_BLOCKLEN */
#define CMD17    (17)        /* READ_SINGLE_BLOCK */
#define CMD18    (18)        /* READ_MULTIPLE_BLOCK */
#define CMD23    (23)        /* SET_BLOCK_COUNT */
#define ACMD23   (0x80+23)   /* SET_WR_BLK_ERASE_COUNT (SDC) */
#define CMD24    (24)        /* WRITE_BLOCK */
#define CMD25    (25)        /* WRITE_MULTIPLE_BLOCK */
#define CMD41    (41)        /* SEND_OP_COND (ACMD) */
#define CMD55    (55)        /* APP_CMD */
#define CMD58    (58)        /* READ_OCR */

/* Card type flags (CardType) */
#define CT_MMC        0x01            /* MMC ver 3 */
#define CT_SD1        0x02            /* SD ver 1 */
#define CT_SD2        0x04            /* SD ver 2 */
#define CT_SDC        (CT_SD1|CT_SD2) /* SD */
#define CT_BLOCK      0x08            /* Block addressing */


static
DSTATUS Stat = STA_NOINIT;    /* Disk status */

static
BYTE CardType;            /* b0:MMC, b1:SDv1, b2:SDv2, b3:Block addressing */

static char buf[80];

/*-----------------------------------------------------------------------*/
/* Transmit bytes to the MMC (bitbanging)                                */
/*-----------------------------------------------------------------------*/
static
void xmit_mmc (
    const BYTE* buff,    /* Data to be sent */
    UINT bc              /* Number of bytes to send */
)
{
    BYTE d;

    do {
        d = *buff++;    /* Get a byte to be sent */
        if (d & 0x80) DI_H(); else DI_L();    /* bit7 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x40) DI_H(); else DI_L();    /* bit6 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x20) DI_H(); else DI_L();    /* bit5 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x10) DI_H(); else DI_L();    /* bit4 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x08) DI_H(); else DI_L();    /* bit3 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x04) DI_H(); else DI_L();    /* bit2 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x02) DI_H(); else DI_L();    /* bit1 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        if (d & 0x01) DI_H(); else DI_L();    /* bit0 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        DLY_US(10);
        //snprintf(buf, sizeof buf, "sent 0x%02x\r\n", d);
        //UART_1_PutString(buf);
    } while (--bc);
}


/*-----------------------------------------------------------------------*/
/* Receive bytes from the MMC (bitbanging)                               */
/*-----------------------------------------------------------------------*/
static
void rcvr_mmc (
    BYTE *buff,    /* Pointer to read buffer */
    UINT bc        /* Number of bytes to receive */
)
{
    BYTE r;

    DI_H();    /* Send 0xFF */

    do {
        r = 0;   if (DO) r++;    /* bit7 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit6 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit5 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit4 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit3 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit2 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit1 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        r <<= 1; if (DO) r++;    /* bit0 */
        CK_H(); CLK_DELAY(); CK_L(); CLK_DELAY();
        *buff++ = r;            /* Store a received byte */
        DLY_US(10);
        //snprintf(buf, sizeof buf, "received 0x%02x\r\n", r);
        //UART_1_PutString(buf);
    } while (--bc);
}


/*-----------------------------------------------------------------------*/
/* Wait for card ready                                                   */
/*-----------------------------------------------------------------------*/
static
int wait_ready (void)    /* 1:OK, 0:Timeout */
{
    BYTE d;
    UINT tmr;

    for (tmr = 5000; tmr; tmr--) {    /* Wait for ready in timeout of 500ms */
        rcvr_mmc(&d, 1);
        if (d == 0xFF) return 1;
        DLY_US(100);
    }
    return 0;
}


/*-----------------------------------------------------------------------*/
/* Deselect the card and release SPI bus                                 */
/*-----------------------------------------------------------------------*/
static
void deselect (void)
{
    BYTE d;

    CS_H();
开发者_Python百科    rcvr_mmc(&d, 1);
}


/*-----------------------------------------------------------------------*/
/* Select the card and wait for ready                                    */
/*-----------------------------------------------------------------------*/
static
int select (void)    /* 1:OK, 0:Timeout */
{
    CS_L();
    if (!wait_ready()) {
        deselect();
        return 0;
    }
    return 1;
}


/*-----------------------------------------------------------------------*/
/* Receive a data packet from MMC                                        */
/*-----------------------------------------------------------------------*/
static
int rcvr_datablock (    /* 1:OK, 0:Failed */
    BYTE *buff,         /* Data buffer to store received data */
    UINT btr            /* Byte count */
)
{
    BYTE d[2];
    UINT tmr;

    for (tmr = 1000; tmr; tmr--) {  /* Wait for data packet in timeout of 100ms */
        rcvr_mmc(d, 1);
        if (d[0] != 0xFF) break;
        DLY_US(100);
    }
    if (d[0] != 0xFE)
        return 0;                   /* If not valid data token, retutn with error */

    rcvr_mmc(buff, btr);            /* Receive the data block into buffer */
    rcvr_mmc(d, 2);                 /* Discard CRC */

    return 1;                       /* Return with success */
}


/*-----------------------------------------------------------------------*/
/* Send a data packet to MMC                                             */
/*-----------------------------------------------------------------------*/
static
int xmit_datablock (    /* 1:OK, 0:Failed */
    const BYTE *buff,   /* 512 byte data block to be transmitted */
    BYTE token          /* Data/Stop token */
)
{
    BYTE d[2];

    if (!wait_ready())
        return 0;

    d[0] = token;
    xmit_mmc(d, 1);                /* Transmit a token */
    if (token != 0xFD) {           /* Is it data token? */
        xmit_mmc(buff, 512);       /* Transmit the 512 byte data block to MMC */
        rcvr_mmc(d, 2);            /* Dummy CRC (FF,FF) */
        rcvr_mmc(d, 1);            /* Receive data response */
        if ((d[0] & 0x1F) != 0x05) /* If not accepted, return with error */
            return 0;
    }
    return 1;
}


/*-----------------------------------------------------------------------*/
/* Send a command packet to MMC                                          */
/*-----------------------------------------------------------------------*/
static
BYTE send_cmd (        /* Returns command response (bit7==1:Send failed)*/
    BYTE cmd,          /* Command byte */
    DWORD arg          /* Argument */
)
{
    BYTE n, d, buf[6];


    if (cmd & 0x80) {    /* ACMD<n> is the command sequense of CMD55-CMD<n> */
        cmd &= 0x7F;
        n = send_cmd(CMD55, 0);
        if (n > 1) return n;
    }

    /* Select the card and wait for ready */
    deselect();
    if (!select()) {
        return 0xFF;
    }

    /* Send a command packet */
    buf[0] = 0x40 | cmd;            /* Start + Command index */
    buf[1] = (BYTE)(arg >> 24);     /* Argument[31..24] */
    buf[2] = (BYTE)(arg >> 16);     /* Argument[23..16] */
    buf[3] = (BYTE)(arg >> 8);      /* Argument[15..8] */
    buf[4] = (BYTE)arg;             /* Argument[7..0] */
    n = 0x01;                       /* Dummy CRC + Stop */
    if (cmd == CMD0)
        n = 0x95;      /* (valid CRC for CMD0(0)) */
    if (cmd == CMD8)
        n = 0x87;      /* (valid CRC for CMD8(0x1AA)) */
    buf[5] = n;
    xmit_mmc(buf, 6);

    /* Receive command response */
    if (cmd == CMD12)
        rcvr_mmc(&d, 1);    /* Skip a stuff byte when stop reading */
    n = 10;                 /* Wait for a valid response in timeout of 10 attempts */
    do
        rcvr_mmc(&d, 1);
    while ((d & 0x80) && --n);

    return d;            /* Return with the response value */
}


/*--------------------------------------------------------------------------

   Public Functions

---------------------------------------------------------------------------*/

/*-----------------------------------------------------------------------*/
/* Get Disk Status                                                       */
/*-----------------------------------------------------------------------*/
DSTATUS disk_status (
    BYTE drv            /* Drive number (0) */
)
{
    DSTATUS s = Stat;

    if (drv || !INS) {
        s = STA_NODISK | STA_NOINIT;
    } else {
        s &= ~STA_NODISK;
        if (WP)
            s |= STA_PROTECT;
        else
            s &= ~STA_PROTECT;
    }
    Stat = s;

    return s;
}


/*-----------------------------------------------------------------------*/
/* Initialize Disk Drive                                                 */
/*-----------------------------------------------------------------------*/
DSTATUS disk_initialize (
    BYTE drv        /* Physical drive nmuber (0) */
)
{
    BYTE n, ty, cmd, buf[4];
    UINT tmr;
    DSTATUS s;

    INIT_PORT();                /* Initialize control port */

    s = disk_status(drv);        /* Check if card is in the socket */
    if (s & STA_NODISK) return s;

    CS_H();

    for (n = 10; n; n--) rcvr_mmc(buf, 1);    /* 80 dummy clocks */

    ty = 0;
    if (send_cmd(CMD0, 0) == 1) {            /* Enter Idle state */
        if (send_cmd(CMD8, 0x1AA) == 1) {    /* SDv2? */
            rcvr_mmc(buf, 4);                            /* Get trailing return value of R7 resp */
            if (buf[2] == 0x01 && buf[3] == 0xAA) {        /* The card can work at vdd range of 2.7-3.6V */
                for (tmr = 1000; tmr; tmr--) {            /* Wait for leaving idle state (ACMD41 with HCS bit) */
                    if (send_cmd(ACMD41, 1UL << 30) == 0) break;
                    DLY_US(1000);
                }
                if (tmr && send_cmd(CMD58, 0) == 0) {    /* Check CCS bit in the OCR */
                    rcvr_mmc(buf, 4);
                    ty = (buf[0] & 0x40) ? CT_SD2 | CT_BLOCK : CT_SD2;    /* SDv2 */
                }
            }
        } else {                            /* SDv1 or MMCv3 */
            if (send_cmd(ACMD41, 0) <= 1)     {
                ty = CT_SD1; cmd = ACMD41;    /* SDv1 */
            } else {
                ty = CT_MMC; cmd = CMD1;    /* MMCv3 */
            }
            for (tmr = 1000; tmr; tmr--) {            /* Wait for leaving idle state */
                if (send_cmd(ACMD41, 0) == 0) break;
                DLY_US(1000);
            }
            if (!tmr || send_cmd(CMD16, 512) != 0)    /* Set R/W block length to 512 */
                ty = 0;
        }
    }
    else {
        UART_1_PutString("send CMD 0 failed");
    }
    CardType = ty;
    if (ty)        /* Initialization succeded */
        s &= ~STA_NOINIT;
    else        /* Initialization failed */
        s |= STA_NOINIT;
    Stat = s;

    deselect();

    return s;
}


/*-----------------------------------------------------------------------*/
/* Read Sector(s)                                                        */
/*-----------------------------------------------------------------------*/
DRESULT disk_read (
    BYTE drv,            /* Physical drive nmuber (0) */
    BYTE *buff,          /* Pointer to the data buffer to store read data */
    DWORD sector,        /* Start sector number (LBA) */
    BYTE count           /* Sector count (1..128) */
)
{
    DSTATUS s;

    s = disk_status(drv);
    if (s & STA_NOINIT) return RES_NOTRDY;
    if (!count) return RES_PARERR;
    if (!(CardType & CT_BLOCK)) sector *= 512;    /* Convert LBA to byte address if needed */

    if (count == 1) {    /* Single block read */
        if ((send_cmd(CMD17, sector) == 0)    /* READ_SINGLE_BLOCK */
            && rcvr_datablock(buff, 512))
            count = 0;
    }
    else {                /* Multiple block read */
        if (send_cmd(CMD18, sector) == 0) {    /* READ_MULTIPLE_BLOCK */
            do {
                if (!rcvr_datablock(buff, 512)) break;
                buff += 512;
            } while (--count);
            send_cmd(CMD12, 0);                /* STOP_TRANSMISSION */
        }
    }
    deselect();
    return count ? RES_ERROR : RES_OK;
}


/*-----------------------------------------------------------------------*/
/* Write Sector(s)                                                       */
/*-----------------------------------------------------------------------*/
DRESULT disk_write (
    BYTE drv,            /* Physical drive nmuber (0) */
    const BYTE *buff,    /* Pointer to the data to be written */
    DWORD sector,        /* Start sector number (LBA) */
    BYTE count            /* Sector count (1..128) */
)
{
    DSTATUS s;

    s = disk_status(drv);
    if (s & STA_NOINIT) return RES_NOTRDY;
    if (s & STA_PROTECT) return RES_WRPRT;
    if (!count) return RES_PARERR;
    if (!(CardType & CT_BLOCK)) sector *= 512;    /* Convert LBA to byte address if needed */

    if (count == 1) {    /* Single block write */
        if ((send_cmd(CMD24, sector) == 0)    /* WRITE_BLOCK */
            && xmit_datablock(buff, 0xFE))
            count = 0;
    }
    else {                /* Multiple block write */
        if (CardType & CT_SDC) send_cmd(ACMD23, count);
        if (send_cmd(CMD25, sector) == 0) {    /* WRITE_MULTIPLE_BLOCK */
            do {
                if (!xmit_datablock(buff, 0xFC)) break;
                buff += 512;
            } while (--count);
            if (!xmit_datablock(0, 0xFD))    /* STOP_TRAN token */
                count = 1;
        }
    }
    deselect();
    return count ? RES_ERROR : RES_OK;
}


/*-----------------------------------------------------------------------*/
/* Miscellaneous Functions                                               */
/*-----------------------------------------------------------------------*/
DRESULT disk_ioctl (
    BYTE drv,        /* Physical drive nmuber (0) */
    BYTE ctrl,        /* Control code */
    void *buff        /* Buffer to send/receive control data */
)
{
    DRESULT res;
    BYTE n, csd[16];
    WORD cs;

    if (disk_status(drv) & STA_NOINIT)   /* Check if card is in the socket */
        return RES_NOTRDY;

    res = RES_ERROR;
    switch (ctrl) {
        case CTRL_SYNC :        /* Make sure that no pending write process */
            if (select()) {
                deselect();
                res = RES_OK;
            }
            break;

        case GET_SECTOR_COUNT :    /* Get number of sectors on the disk (DWORD) */
            if ((send_cmd(CMD9, 0) == 0) && rcvr_datablock(csd, 16)) {
                if ((csd[0] >> 6) == 1) {    /* SDC ver 2.00 */
                    cs= csd[9] + ((WORD)csd[8] << 8) + 1;
                    *(DWORD*)buff = (DWORD)cs << 10;
                } else {                    /* SDC ver 1.XX or MMC */
                    n = (csd[5] & 15) + ((csd[10] & 128) >> 7) + ((csd[9] & 3) << 1) + 2;
                    cs = (csd[8] >> 6) + ((WORD)csd[7] << 2) + ((WORD)(csd[6] & 3) << 10) + 1;
                    *(DWORD*)buff = (DWORD)cs << (n - 9);
                }
                res = RES_OK;
            }
            break;

        case GET_BLOCK_SIZE :    /* Get erase block size in unit of sector (DWORD) */
            *(DWORD*)buff = 128;
            res = RES_OK;
            break;

        default:
            res = RES_PARERR;
    }
    deselect();
    return res;
}

---

Normally, you can put pull-up resistors when more than one SD card is connected to the same interface lines. In particular, the signals DI, DO, and CLK becomes floating when you deselect and select another card.

Otherwise, I can imagine that it also has an impact on the length of the track between host and slave, in this case the microSD card.

I see the pullup resistors in many example circuits that you find on the Internet.

---

According to the datasheet of the microSD card from Samsung, the DO signal (in SPI mode) is defined as a push-pull-output. This means that a external pull-up resistor isn't need on this signal.