CMD6 for setting High Speed Mode

SdFat/src/SdFat.h

 #endif  // ARDUINO
 //------------------------------------------------------------------------------
 /** SdFat version YYYYMMDD */
-#define SD_FAT_VERSION 20160427
+#define SD_FAT_VERSION 20160430
 //==============================================================================
 /**
  * \class SdBaseFile

SdFat/src/SdSpiCard/SdInfo.h

 uint8_t const SD_CARD_ERROR_READ_CRC = 0X1B;
 /** SPI DMA error */
 uint8_t const SD_CARD_ERROR_SPI_DMA = 0X1C;
+/** CMD6 not accepted */
+uint8_t const SD_CARD_ERROR_CMD6 = 0X1D;
 //------------------------------------------------------------------------------
 // card types
 /** Standard capacity V1 SD card */
 // SD card commands
 /** GO_IDLE_STATE - init card in spi mode if CS low */
 uint8_t const CMD0 = 0X00;
+/** SWITCH_FUNC - Switch Function Command */
+uint8_t const CMD6 = 0X06;
 /** SEND_IF_COND - verify SD Memory Card interface operating condition.*/
 uint8_t const CMD8 = 0X08;
 /** SEND_CSD - read the Card Specific Data (CSD register) */

SdFat/src/SdSpiCard/SdSpiCard.cpp

   return false;
 }
 //------------------------------------------------------------------------------
+bool SdSpiCard::sendCmd6(uint32_t arg, uint8_t* status) {
+  if (cardCommand(CMD6, arg)) {
+    error(SD_CARD_ERROR_CMD6);
+    goto fail;
+  }
+  if (!readData(status, 64)) {
+    goto fail;
+  }
+  chipSelectHigh();
+  return true;
+
+fail:
+  chipSelectHigh();
+  return false;
+}
+//------------------------------------------------------------------------------
+bool SdSpiCard::setHighSpeedMode(uint8_t divisor) {
+  uint8_t status[64];
+  uint8_t saveDivisor = m_sckDivisor;
+  setSckDivisor(128);
+  if (!sendCmd6(0X00FFFFFF, status) || (2 & status[13]) == 0 ||
+      !sendCmd6(0X80FFFFF1, status) || (status[16] & 0XF) != 1) {
+    setSckDivisor(saveDivisor);
+    return false;
+  }
+  setSckDivisor(divisor);
+  return true;
+}
+//------------------------------------------------------------------------------
 // wait for card to go not busy
 bool SdSpiCard::waitNotBusy(uint16_t timeoutMillis) {
   unsigned t0 = millis();

SdFat/src/SdSpiCard/SdSpiCard.h

   }
   /** \return the SD chip select status, true if slected else false. */
   bool selected() {return m_selected;}
+  /**  Send CMD6 - Switch Function Command
+   *
+   * param[in] arg 32-bit argument to CMD6.
+   * param[out] status - 64 byte status returned by CMD6.
+   * \return true if the command was accepted else false.
+   */
+  bool sendCmd6(uint32_t arg, uint8_t* status);
+  /** Set High Speed Bus Mode.
+   *
+   * param[in] divisor new value for SPI SCK divisor.
+   * \return true if successful else false.
+   */
+  bool setHighSpeedMode(uint8_t divisor);
+  /** Set SCK divisor.
+   *  param[in] sckDivisor value for divisor.
+   */
+  void setSckDivisor(uint8_t sckDivisor) {
+    m_sckDivisor = sckDivisor;
+  }
   /** Return the card type: SD V1, SD V2 or SDHC
    * \return 0 - SD V1, 1 - SD V2, or 3 - SDHC.
    */