C++ spiRec函数代码示例

//------------------------------------------------------------------------------
// send one block of data for write block or write multiple blocks
uint8_t Sd2Card::writeData(uint8_t token, const uint8_t* src) {

  spiSend(token);
  for (uint16_t i = 0; i < 512; i++) {
    spiSend(src[i]);
  }

  spiSend(0xff);  // dummy crc
  spiSend(0xff);  // dummy crc

  status_ = spiRec();
  if ((status_ & DATA_RES_MASK) != DATA_RES_ACCEPTED) {
    error(SD_CARD_ERROR_WRITE);
    chipSelectHigh();
    return false;
  }
  return true;
}

/** Wait for start block token */
uint8_t Sd2Card::waitStartBlock(void) {
  uint16_t t0 = millis();
  while ((status_ = spiRec()) == 0XFF) {
    if (((uint16_t)millis() - t0) > SD_READ_TIMEOUT) {
      error(SD_CARD_ERROR_READ_TIMEOUT);
      goto fail;
    }
  }
  if (status_ != DATA_START_BLOCK) {
    error(SD_CARD_ERROR_READ);
    goto fail;
  }
  return true;

 fail:
  chipSelectHigh();
  return false;
}

/** Skip remaining data in a block when in partial block read mode. */
void Sd2Card::readEnd(void) {
  if (inBlock_) {
      // skip data and crc
#ifdef OPTIMIZE_HARDWARE_SPI
    // optimize skip for hardware
    SPDR = 0XFF;
    while (offset_++ < 513) {
      while (!(SPSR & (1 << SPIF)));
      SPDR = 0XFF;
    }
    // wait for last crc byte
    while (!(SPSR & (1 << SPIF)));
#else  // OPTIMIZE_HARDWARE_SPI
    while (offset_++ < 514) spiRec();
#endif  // OPTIMIZE_HARDWARE_SPI
    chipSelectHigh();
    inBlock_ = 0;
  }
}

/** Wait for start block token */
int Sd2Card::waitStartBlock(void) {
	//unsigned t0 = millis();
	unsigned count = 30000;
	while ((status_ = spiRec()) == 0XFF) {
		if (count-- == 0) {
			error(SD_CARD_ERROR_READ_TIMEOUT);
			goto fail;
		}
	}

  if (status_ != DATA_START_BLOCK) {
    error(SD_CARD_ERROR_READ);
    goto fail;
  }
  return true;

 fail:
  chipSelectHigh();
  return false;
}

/** Skip remaining data in a block when in partial block read mode. */
void Sd2Card::readEnd(void) {
  if (inBlock_) {
      // skip data and crc
#ifdef SPI_DMA
        dma_setup_transfer(DMA1, DMA_CH3, &SPI1->regs->DR, DMA_SIZE_8BITS, ack, DMA_SIZE_8BITS,
                           (/*DMA_MINC_MODE | DMA_CIRC_MODE |*/ DMA_FROM_MEM | DMA_TRNS_CMPLT | DMA_TRNS_ERR));
        dma_attach_interrupt(DMA1, DMA_CH3, DMAEvent);
        dma_set_priority(DMA1, DMA_CH3, DMA_PRIORITY_VERY_HIGH);
        dma_set_num_transfers(DMA1, DMA_CH3, SPI_BUFF_SIZE + 1 - offset_);

        dmaActive = true;
        dma_enable(DMA1, DMA_CH3);

        while(dmaActive)delayMicroseconds(1);
        dma_disable(DMA1, DMA_CH3);
#else  // SPI_DMA
    while (offset_++ < 514) spiRec();
#endif  // SPI_DMA
    chipSelectHigh();
    inBlock_ = 0;
  }
}

/**
 * Writes a 512 byte block to an SD card.
 *
 * \param[in] blockNumber Logical block to be written.
 * \param[in] src Pointer to the location of the data to be written.
 * \return The value one, true, is returned for success and
 * the value zero, false, is returned for failure.
 */
uint8_t Sd2Card::writeBlock(uint32_t blockNumber, const uint8_t* src) {
#if SD_PROTECT_BLOCK_ZERO
  // don't allow write to first block
  if (blockNumber == 0) {
    error(SD_CARD_ERROR_WRITE_BLOCK_ZERO);
    Serial.println("Error: Write block zero");
    goto fail;
  }
#endif  // SD_PROTECT_BLOCK_ZERO

  // use address if not SDHC card
  if (type() != SD_CARD_TYPE_SDHC) blockNumber <<= 9;
  if (cardCommand(CMD24, blockNumber)) {
	Serial.println("Error: CMD42");
	error(SD_CARD_ERROR_CMD24);
	goto fail;
  }
  if (!writeData(DATA_START_BLOCK, src)) goto fail;

  // wait for flash programming to complete
  if (!waitNotBusy(SD_WRITE_TIMEOUT)) {
    error(SD_CARD_ERROR_WRITE_TIMEOUT);
    Serial.println("Error: Write timeout");
    goto fail;
  }
  // response is r2 so get and check two bytes for nonzero
  if (cardCommand(CMD13, 0) || spiRec()) {
    error(SD_CARD_ERROR_WRITE_PROGRAMMING);
    Serial.println("Error: Write programming");
    goto fail;
  }
  chipSelectHigh();
  return true;

 fail:
  chipSelectHigh();
  Serial.println("Error: Sd2Card::writeBlock");
  return false;
}

//------------------------------------------------------------------------------
// send one block of data for write block or write multiple blocks
uint8_t Sd2Card::writeData(uint8_t token, const uint8_t* src) {
#ifdef OPTIMIZE_HARDWARE_SPI
    /*
      // send data - optimized loop
      SPDR = token;

      // send two byte per iteration
      for (uint16_t i = 0; i < 512; i += 2) {
        while (!(SPSR & (1 << SPIF)));
        SPDR = src[i];
        while (!(SPSR & (1 << SPIF)));
        SPDR = src[i+1];
      }

      // wait for last data byte
      while (!(SPSR & (1 << SPIF)));
    */
#else  // OPTIMIZE_HARDWARE_SPI
    spiSend(token);
    for (uint16_t i = 0; i < 512; i++)
    {
        spiSend(src[i]);
    }
    //spiSend(src, 512);
#endif  // OPTIMIZE_HARDWARE_SPI
    spiSend(0xff);  // dummy crc
    spiSend(0xff);  // dummy crc

    status_ = spiRec();
    if ((status_ & DATA_RES_MASK) != DATA_RES_ACCEPTED)
    {
        error(SD_CARD_ERROR_WRITE);
        chipSelectHigh();
        SerialDebug.println("Error: Write");
        SerialDebug.println("Error: Sd2Card::writeData()");
        return false;
    }
    return true;
}

/** Skip remaining data in a block when in partial block read mode. */
void Sd2Card::readEnd(void) {
  if (inBlock_) {
      // skip data and crc
#if defined(USE_TEENSY3_SPI)
    if (offset_ < 514) {
      spiRecIgnore(514 - offset_);
      offset_ = 514;
    }
#elif defined(OPTIMIZE_HARDWARE_SPI)
    // optimize skip for hardware
    SPDR = 0XFF;
    while (offset_++ < 513) {
      while (!(SPSR & (1 << SPIF)));
      SPDR = 0XFF;
    }
    // wait for last crc byte
    while (!(SPSR & (1 << SPIF)));
#else  // OPTIMIZE_HARDWARE_SPI
    while (offset_++ < 514) spiRec();
#endif  // OPTIMIZE_HARDWARE_SPI
    chipSelectHigh();
    inBlock_ = 0;
  }
}

//------------------------------------------------------------------------------
// send command and return error code.  Return zero for OK
uint8_t Sd2Card::cardCommand(uint8_t cmd, uint32_t arg) {
  // end read if in partialBlockRead mode
  readEnd();

  // select card
  chipSelectLow();

  // wait up to 300 ms if busy
  waitNotBusy(300);

  // send command
  spiSend(cmd | 0x40);

#ifdef ESP8266
  // send argument
  SPI.write32(arg, true);
#else
  // send argument
  for (int8_t s = 24; s >= 0; s -= 8) spiSend(arg >> s);
#endif


  // send CRC
  uint8_t crc = 0xFF;
  if (cmd == CMD0) crc = 0x95;  // correct crc for CMD0 with arg 0
  if (cmd == CMD8) crc = 0x87;  // correct crc for CMD8 with arg 0X1AA
  spiSend(crc);

  // wait for response
  for (uint8_t i = 0; ((status_ = spiRec()) & 0x80) && i != 0xFF; i++)
    ;
  #ifdef ESP8266
  optimistic_yield(10000);
  #endif
  return status_;
}

/**
    Read part of a 512 byte block from an SD card.

    \param[in] block Logical block to be read.
    \param[in] offset Number of bytes to skip at start of block
    \param[out] dst Pointer to the location that will receive the data.
    \param[in] count Number of bytes to read
    \return The value one, true, is returned for success and
    the value zero, false, is returned for failure.
*/
uint8_t Sd2Card::readData(uint32_t block, uint16_t offset, uint16_t count, uint8_t* dst)
{
//    uint16_t n;
    if (count == 0)
    {
        return true;
    }
    if ((count + offset) > 512)
    {
        goto fail;
    }
    if (!inBlock_ || block != block_ || offset < offset_)
    {
        block_ = block;
        // use address if not SDHC card
        if (type() != SD_CARD_TYPE_SDHC)
        {
            block <<= 9;
        }
        if (cardCommand(CMD17, block))
        {
            error(SD_CARD_ERROR_CMD17);
            goto fail;
        }
        if (!waitStartBlock())
        {
            goto fail;
        }
        offset_ = 0;
        inBlock_ = 1;
    }

#ifdef OPTIMIZE_HARDWARE_SPI
    // start first spi transfer
    SPDR = 0XFF;

    // skip data before offset
    for (; offset_ < offset; offset_++)
    {
        while (!(SPSR & (1 << SPIF)));
        SPDR = 0XFF;
    }
    // transfer data
    n = count - 1;
    for (uint16_t i = 0; i < n; i++)
    {
        while (!(SPSR & (1 << SPIF)));
        dst[i] = SPDR;
        SPDR = 0XFF;
    }
    // wait for last byte
    while (!(SPSR & (1 << SPIF)));
    dst[n] = SPDR;

#else  // OPTIMIZE_HARDWARE_SPI

    // skip data before offset
    for (; offset_ < offset; offset_++)
    {
        spiRec();
    }
    // transfer data
    for (uint16_t i = 0; i < count; i++)
    {
        dst[i] = spiRec();
    }
#endif  // OPTIMIZE_HARDWARE_SPI

    offset_ += count;
    if (!partialBlockRead_ || offset_ >= 512)
    {
        // read rest of data, checksum and set chip select high
        readEnd();
    }
    return true;

fail:
    chipSelectHigh();
    return false;
}

/**
 * Initialize an SD flash memory card.
 *
 * \param[in] sckRateID SPI clock rate selector. See setSckRate().
 * \param[in] chipSelectPin SD chip select pin number.
 *
 * \return The value one, true, is returned for success and
 * the value zero, false, is returned for failure.  The reason for failure
 * can be determined by calling errorCode() and errorData().
 */
uint8_t Sd2Card::init(uint8_t sckRateID, uint8_t chipSelectPin) {
  errorCode_ = inBlock_ = partialBlockRead_ = type_ = 0;

  // 16-bit init start time allows over a minute
  uint16_t t0 = (uint16_t)millis();
  uint32_t arg;

  SPI2CON = 0;

  DDPCONbits.JTAGEN = 0;

  AD1PCFG = 0xFFFF;

  chipSelectPin_ = chipSelectPin;

  pinMode(chipSelectPin_, OUTPUT);

  PORTSetPinsDigitalOut(prtSCK, bnSCK);
  PORTSetPinsDigitalOut(prtSDO, bnSDO);
  PORTSetPinsDigitalIn(prtSDI, bnSDI);
  
  // set pin modes
  chipSelectHigh();

  // must supply min of 74 clock cycles with CS high.
  for (uint8_t i = 0; i < 10; i++) spiSend(0XFF);

  chipSelectLow();

  // command to go idle in SPI mode
  while ((status_ = cardCommand(CMD0, 0)) != R1_IDLE_STATE) {
    if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_CMD0);
      goto fail;
    }
  }
  // check SD version
  if ((cardCommand(CMD8, 0x1AA) & R1_ILLEGAL_COMMAND)) {
    type(SD_CARD_TYPE_SD1);
  } else {
    // only need last byte of r7 response
    for (uint8_t i = 0; i < 4; i++) status_ = spiRec();
    if (status_ != 0XAA) {
      error(SD_CARD_ERROR_CMD8);
      goto fail;
    }
    type(SD_CARD_TYPE_SD2);
  }
  // initialize card and send host supports SDHC if SD2
  arg = type() == SD_CARD_TYPE_SD2 ? 0X40000000 : 0;

  while ((status_ = cardAcmd(ACMD41, arg)) != R1_READY_STATE) {
    // check for timeout
    if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_ACMD41);
      goto fail;
    }
  }
  // if SD2 read OCR register to check for SDHC card
  if (type() == SD_CARD_TYPE_SD2) {
    if (cardCommand(CMD58, 0)) {
      error(SD_CARD_ERROR_CMD58);
      goto fail;
    }
    if ((spiRec() & 0XC0) == 0XC0) type(SD_CARD_TYPE_SDHC);
    // discard rest of ocr - contains allowed voltage range
    for (uint8_t i = 0; i < 3; i++) spiRec();
  }
  chipSelectHigh();

#ifndef SOFTWARE_SPI
  return setSckRate(sckRateID);
#else  // SOFTWARE_SPI
  return true;
#endif  // SOFTWARE_SPI

 fail:
  chipSelectHigh();
  return false;
}

//.........这里部分代码省略.........
    //#endif // SOFTWARE_SPI


    // Hardware card detection
    if (cardDetectionPin_ >= 0)
    {
        //        debugln("hardware card detection %i should be %i", digitalRead(cardDetectionPin_), level);
        if (digitalRead(cardDetectionPin_) != level_)
        {
            // Serial.println("*** hardware failure");
            error(SD_CARD_ERROR_CMD0);
            // I don't like goto but this is how it is implemented
            goto fail;
        }
    }

    // Software card detection

    // must supply min of 74 clock cycles with CS high.
    for (uint8_t i = 0; i < 10; i++)
    {
        spiSend(0xff);
    }

    chipSelectLow();

    // Serial.print("software card detection ");


    // command to go idle in SPI mode
    while ((status_ = cardCommand(CMD0, 0)) != R1_IDLE_STATE)
    {
        if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT)
        {
            error(SD_CARD_ERROR_CMD0);
            // Serial.println("*** software failure");
            goto fail;
        }
    }
    // check SD version
    if ((cardCommand(CMD8, 0x1AA) & R1_ILLEGAL_COMMAND))
    {
        type(SD_CARD_TYPE_SD1);
    }
    else
    {
        // only need last byte of r7 response
        for (uint8_t i = 0; i < 4; i++)
        {
            status_ = spiRec();
        }
        if (status_ != 0xaa)
        {
            error(SD_CARD_ERROR_CMD8);
            goto fail;
        }
        type(SD_CARD_TYPE_SD2);
    }
    // initialize card and send host supports SDHC if SD2
    arg = type() == SD_CARD_TYPE_SD2 ? 0x40000000 : 0;

    while ((status_ = cardAcmd(ACMD41, arg)) != R1_READY_STATE)
    {
        // check for timeout
        if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT)
        {
            error(SD_CARD_ERROR_ACMD41);
            goto fail;
        }
    }
    // if SD2 read OCR register to check for SDHC card
    if (type() == SD_CARD_TYPE_SD2)
    {
        if (cardCommand(CMD58, 0))
        {
            error(SD_CARD_ERROR_CMD58);
            goto fail;
        }
        if ((spiRec() & 0xc0) == 0xc0)
        {
            type(SD_CARD_TYPE_SDHC);
        }
        // discard rest of ocr - contains allowed voltage range
        for (uint8_t i = 0; i < 3; i++)
        {
            spiRec();
        }
    }
    chipSelectHigh();

#ifndef SOFTWARE_SPI
    return setSckRate(sckRateID);
#else  // SOFTWARE_SPI
    return true;
#endif  // SOFTWARE_SPI

fail:
    chipSelectHigh();
    return false;
}

/**
 * Initialize an SD flash memory card.
 *
 * \param[in] sckRateID SPI clock rate selector. See setSckRate().
 * \param[in] chipSelectPin SD chip select pin number.
 *
 * \return The value one, true, is returned for success and
 * the value zero, false, is returned for failure.  The reason for failure
 * can be determined by calling errorCode() and errorData().
 */
uint8_t Sd2Card::init(uint8_t sckRateID, uint8_t chipSelectPin) {
  errorCode_ = inBlock_ = partialBlockRead_ = type_ = 0;
  chipSelectPin_ = chipSelectPin;
  // 16-bit init start time allows over a minute
  uint16_t t0 = (uint16_t)millis();
  uint32_t arg;

  // set pin modes
  pinMode(chipSelectPin_, OUTPUT);
  digitalWrite(chipSelectPin_, HIGH);
#ifndef USE_SPI_LIB
  pinMode(SPI_MISO_PIN, INPUT);
  pinMode(SPI_MOSI_PIN, OUTPUT);
  pinMode(SPI_SCK_PIN, OUTPUT);
#endif

#ifndef SOFTWARE_SPI
#ifndef USE_SPI_LIB
  // SS must be in output mode even it is not chip select
  pinMode(SS_PIN, OUTPUT);
  digitalWrite(SS_PIN, HIGH); // disable any SPI device using hardware SS pin
  // Enable SPI, Master, clock rate f_osc/128
  SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1) | (1 << SPR0);
  // clear double speed
  SPSR &= ~(1 << SPI2X);
#else // USE_SPI_LIB
  SPI.begin();
  settings = SPISettings(250000, MSBFIRST, SPI_MODE0);
#endif // USE_SPI_LIB
#endif // SOFTWARE_SPI

  // must supply min of 74 clock cycles with CS high.
#ifdef USE_SPI_LIB
  SPI.beginTransaction(settings);
#endif
  for (uint8_t i = 0; i < 10; i++) spiSend(0XFF);
#ifdef USE_SPI_LIB
  SPI.endTransaction();
#endif

  chipSelectLow();

  // command to go idle in SPI mode
  while ((status_ = cardCommand(CMD0, 0)) != R1_IDLE_STATE) {
    if (((uint16_t)(millis() - t0)) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_CMD0);
      goto fail;
    }
  }
  // check SD version
  if ((cardCommand(CMD8, 0x1AA) & R1_ILLEGAL_COMMAND)) {
    type(SD_CARD_TYPE_SD1);
  } else {
    // only need last byte of r7 response
    for (uint8_t i = 0; i < 4; i++) status_ = spiRec();
    if (status_ != 0XAA) {
      error(SD_CARD_ERROR_CMD8);
      goto fail;
    }
    type(SD_CARD_TYPE_SD2);
  }
  // initialize card and send host supports SDHC if SD2
  arg = type() == SD_CARD_TYPE_SD2 ? 0X40000000 : 0;

  while ((status_ = cardAcmd(ACMD41, arg)) != R1_READY_STATE) {
    // check for timeout
    if (((uint16_t)(millis() - t0)) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_ACMD41);
      goto fail;
    }
  }
  // if SD2 read OCR register to check for SDHC card
  if (type() == SD_CARD_TYPE_SD2) {
    if (cardCommand(CMD58, 0)) {
      error(SD_CARD_ERROR_CMD58);
      goto fail;
    }
    if ((spiRec() & 0XC0) == 0XC0) type(SD_CARD_TYPE_SDHC);
    // discard rest of ocr - contains allowed voltage range
    for (uint8_t i = 0; i < 3; i++) spiRec();
  }
  chipSelectHigh();

#ifndef SOFTWARE_SPI
  return setSckRate(sckRateID);
#else  // SOFTWARE_SPI
  return true;
#endif  // SOFTWARE_SPI

 fail:
//.........这里部分代码省略.........

/**
 * Initialize a SD flash memory card.
 *
 * \param[in] slow If \a slow is false (zero) the SPI bus will
 * be initialize at a speed of 8 Mhz.  If \a slow is true (nonzero)
 * the SPI bus will be initialize a speed of 4 Mhz. This may be helpful
 * for some SD cards with Version 1.0 of the Adafruit Wave Shield.
 *
 * \return The value one, true, is returned for success and
 * the value zero, false, is returned for failure. 
 *
 */  
uint8_t SdReader::init(uint8_t slow) {
  uint8_t ocr[4];
  uint8_t r;
  
  pinMode(SS, OUTPUT);
  digitalWrite(SS, HIGH);
  pinMode(MOSI, OUTPUT);
  pinMode(MISO_PIN, INPUT);
  pinMode(SCK, OUTPUT);
  
#if SPI_INIT_SLOW
  // Enable SPI, Master, clock rate f_osc/128
  SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1) | (1 << SPR0);
#else  // SPI_INIT_SLOW
  // Enable SPI, Master, clock rate f_osc/64
  SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1);
#endif  // SPI_INIT_SLOW
  
  // must supply min of 74 clock cycles with CS high.
  for (uint8_t i = 0; i < 10; i++) spiSend(0XFF);
  
  // next two lines prevent re-init hang by cards that were in partial read
  spiSSLow();
  for (uint16_t i = 0; i <= 512; i++) spiRec();
  
  // command to go idle in SPI mode
  for (uint8_t retry = 0; ; retry++) {
    if ((r = cardCommand(CMD0, 0)) ==  R1_IDLE_STATE) break;
    if (retry == 10) {
      error(SD_CARD_ERROR_CMD0, r);
      return false;
    }
  }
  // check SD version
  r = cardCommand(CMD8, 0x1AA);
  if (r == R1_IDLE_STATE) {
    for(uint8_t i = 0; i < 4; i++) {
      r = spiRec();
    }
    if (r != 0XAA) {
      error(SD_CARD_ERROR_CMD8_ECHO, r);
      return false;
    }
    type(SD_CARD_TYPE_SD2);
  }
  else if (r & R1_ILLEGAL_COMMAND) {
    type(SD_CARD_TYPE_SD1);
  }
  else {
    error(SD_CARD_ERROR_CMD8, r);
  }
  // initialize card and send host supports SDHC if SD2
  for (uint16_t t0 = millis();;) {
    cardCommand(CMD55, 0);
    r = cardCommand(ACMD41, type() == SD_CARD_TYPE_SD2 ? 0X40000000 : 0);
    if (r == R1_READY_STATE) break;
    
    // timeout after 2 seconds
    if (((uint16_t)millis() - t0) > 2000) {
      error(SD_CARD_ERROR_ACMD41);
      return false;
    }
  }
  // if SD2 read OCR register to check for SDHC card
  if (type() == SD_CARD_TYPE_SD2) {
    if(cardCommand(CMD58, 0)) {
      error(SD_CARD_ERROR_CMD58);
      return false;
    }
    if ((spiRec() & 0XC0) == 0XC0) type(SD_CARD_TYPE_SDHC);
    
    // discard rest of ocr
    for (uint8_t i = 0; i < 3; i++) spiRec();
  }

  // use max SPI frequency unless slow is true
  SPCR &= ~((1 << SPR1) | (1 << SPR0)); // f_OSC/4
  
  if (!slow) SPSR |= (1 << SPI2X); // Doubled Clock Frequency: f_OSC/2
  spiSSHigh();
  return true;
}

/**
 * Initialize an SD flash memory card.
 *
 * \return The value one, true, is returned for success and
 * the value zero, false, is returned for failure.  The reason for failure
 * can be determined by calling errorCode() and errorData().
 */
uint8_t Sd2Card::init() {
  errorCode_ = inBlock_ = partialBlockRead_ = type_ = 0;
  chipSelectPin_ = SD_CHIP_SELECT_PIN;
  // 16-bit init start time allows over a minute
  uint16_t t0 = (uint16_t)millis();
  uint32_t arg;

  // set pin modes
  pinMode(chipSelectPin_, OUTPUT);
  chipSelectHigh();
  pinMode(SPI_MISO_PIN, INPUT);
  pinMode(SPI_MOSI_PIN, OUTPUT);
  pinMode(SPI_SCK_PIN, OUTPUT);


  // must supply min of 74 clock cycles with CS high.
  for (uint8_t i = 0; i < 10; i++) spiSend(0XFF);

  chipSelectLow();

  // command to go idle in SPI mode
  while ((status_ = cardCommand(CMD0, 0)) != R1_IDLE_STATE) {
    if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_CMD0);
      goto fail;
    }
  }
  // check SD version
  if ((cardCommand(CMD8, 0x1AA) & R1_ILLEGAL_COMMAND)) {
    type(SD_CARD_TYPE_SD1);
  } else {
    // only need last byte of r7 response
    for (uint8_t i = 0; i < 4; i++) status_ = spiRec();
    if (status_ != 0XAA) {
      error(SD_CARD_ERROR_CMD8);
      goto fail;
    }
    type(SD_CARD_TYPE_SD2);
  }
  // initialize card and send host supports SDHC if SD2
  arg = type() == SD_CARD_TYPE_SD2 ? 0X40000000 : 0;

  while ((status_ = cardAcmd(ACMD41, arg)) != R1_READY_STATE) {
    // check for timeout
    if (((uint16_t)millis() - t0) > SD_INIT_TIMEOUT) {
      error(SD_CARD_ERROR_ACMD41);
      goto fail;
    }
  }
  // if SD2 read OCR register to check for SDHC card
  if (type() == SD_CARD_TYPE_SD2) {
    if (cardCommand(CMD58, 0)) {
      error(SD_CARD_ERROR_CMD58);
      goto fail;
    }
    if ((spiRec() & 0XC0) == 0XC0) type(SD_CARD_TYPE_SDHC);
    // discard rest of ocr - contains allowed voltage range
    for (uint8_t i = 0; i < 3; i++) spiRec();
  }
  chipSelectHigh();

  return true;

 fail:
  chipSelectHigh();
  return false;
}