Revision 0:2a6d8a096edc, committed 2014-07-29

Comitter:

neilt6

Date:

Tue Jul 29 20:12:23 2014 +0000

Child:

1:25f4ba436b81

Commit message:

Initial commit

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CRC16.cpp	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,67 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CRC16.h"
+
+namespace
+{
+const unsigned short m_CRC16Table[256] = {
+    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
+    0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
+    0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
+    0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
+    0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
+    0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
+    0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
+    0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
+    0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
+    0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
+    0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
+    0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
+    0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
+    0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
+    0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
+    0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
+    0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
+    0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
+    0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
+    0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
+    0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
+    0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
+    0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
+    0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
+    0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
+    0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
+    0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
+    0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
+    0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
+    0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
+    0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
+    0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
+};
+}
+
+unsigned short CRC16(const char* data, int length)
+{
+    //Calculate the CRC16 checksum for the specified data block
+    unsigned short crc = 0;
+    for (int i = 0; i < length; i++) {
+        crc = (crc << 8) ^ m_CRC16Table[((crc >> 8) ^ data[i]) & 0x00FF];
+    }
+
+    //Return the calculated checksum
+    return crc;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CRC16.h	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,24 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CRC16_H
+#define CRC16_H
+
+#include "mbed.h"
+
+unsigned short CRC16(const char* data, int length);
+
+#endif

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CRC7.cpp	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,67 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CRC7.h"
+
+namespace
+{
+const char m_CRC7Table[] = {
+    0x00, 0x09, 0x12, 0x1B, 0x24, 0x2D, 0x36, 0x3F,
+    0x48, 0x41, 0x5A, 0x53, 0x6C, 0x65, 0x7E, 0x77,
+    0x19, 0x10, 0x0B, 0x02, 0x3D, 0x34, 0x2F, 0x26,
+    0x51, 0x58, 0x43, 0x4A, 0x75, 0x7C, 0x67, 0x6E,
+    0x32, 0x3B, 0x20, 0x29, 0x16, 0x1F, 0x04, 0x0D,
+    0x7A, 0x73, 0x68, 0x61, 0x5E, 0x57, 0x4C, 0x45,
+    0x2B, 0x22, 0x39, 0x30, 0x0F, 0x06, 0x1D, 0x14,
+    0x63, 0x6A, 0x71, 0x78, 0x47, 0x4E, 0x55, 0x5C,
+    0x64, 0x6D, 0x76, 0x7F, 0x40, 0x49, 0x52, 0x5B,
+    0x2C, 0x25, 0x3E, 0x37, 0x08, 0x01, 0x1A, 0x13,
+    0x7D, 0x74, 0x6F, 0x66, 0x59, 0x50, 0x4B, 0x42,
+    0x35, 0x3C, 0x27, 0x2E, 0x11, 0x18, 0x03, 0x0A,
+    0x56, 0x5F, 0x44, 0x4D, 0x72, 0x7B, 0x60, 0x69,
+    0x1E, 0x17, 0x0C, 0x05, 0x3A, 0x33, 0x28, 0x21,
+    0x4F, 0x46, 0x5D, 0x54, 0x6B, 0x62, 0x79, 0x70,
+    0x07, 0x0E, 0x15, 0x1C, 0x23, 0x2A, 0x31, 0x38,
+    0x41, 0x48, 0x53, 0x5A, 0x65, 0x6C, 0x77, 0x7E,
+    0x09, 0x00, 0x1B, 0x12, 0x2D, 0x24, 0x3F, 0x36,
+    0x58, 0x51, 0x4A, 0x43, 0x7C, 0x75, 0x6E, 0x67,
+    0x10, 0x19, 0x02, 0x0B, 0x34, 0x3D, 0x26, 0x2F,
+    0x73, 0x7A, 0x61, 0x68, 0x57, 0x5E, 0x45, 0x4C,
+    0x3B, 0x32, 0x29, 0x20, 0x1F, 0x16, 0x0D, 0x04,
+    0x6A, 0x63, 0x78, 0x71, 0x4E, 0x47, 0x5C, 0x55,
+    0x22, 0x2B, 0x30, 0x39, 0x06, 0x0F, 0x14, 0x1D,
+    0x25, 0x2C, 0x37, 0x3E, 0x01, 0x08, 0x13, 0x1A,
+    0x6D, 0x64, 0x7F, 0x76, 0x49, 0x40, 0x5B, 0x52,
+    0x3C, 0x35, 0x2E, 0x27, 0x18, 0x11, 0x0A, 0x03,
+    0x74, 0x7D, 0x66, 0x6F, 0x50, 0x59, 0x42, 0x4B,
+    0x17, 0x1E, 0x05, 0x0C, 0x33, 0x3A, 0x21, 0x28,
+    0x5F, 0x56, 0x4D, 0x44, 0x7B, 0x72, 0x69, 0x60,
+    0x0E, 0x07, 0x1C, 0x15, 0x2A, 0x23, 0x38, 0x31,
+    0x46, 0x4F, 0x54, 0x5D, 0x62, 0x6B, 0x70, 0x79
+};
+}
+
+char CRC7(const char* data, int length)
+{
+    //Calculate the CRC7 checksum for the specified data block
+    char crc = 0;
+    for (int i = 0; i < length; i++) {
+        crc = m_CRC7Table[(crc << 1) ^ data[i]];
+    }
+
+    //Return the calculated checksum
+    return crc;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CRC7.h	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,24 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CRC7_H
+#define CRC7_H
+
+#include "mbed.h"
+
+char CRC7(const char* data, int length);
+
+#endif

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FATFileSystem.lib	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/teams/mbed-official/code/FATFileSystem/#e960e2b81a3c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SDFileSystem.cpp	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,496 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "SDFileSystem.h"
+#include "diskio.h"
+#include "CRC7.h"
+#include "CRC16.h"
+
+SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, PinName cd, const char* name, int hz) : FATFileSystem(name), m_SPI(mosi, miso, sclk), m_CS(cs, 1), m_CD(cd)
+{
+    //Initialize the member variables
+    m_SpiFreq = hz;
+    m_Status = STA_NOINIT;
+    m_CardType = CARD_NONE;
+
+    //Configure the SPI bus
+    m_SPI.format(8, 0);
+
+    //Configure the card detect pin
+    m_CD.mode(PullUp);
+    m_CD.fall(this, &SDFileSystem::checkSocket);
+}
+
+SDFileSystem::CardType SDFileSystem::card_type()
+{
+    //Check the card socket
+    checkSocket();
+
+    //If a card is present but not initialized, initialize it
+    if (!(m_Status & STA_NODISK) && (m_Status & STA_NOINIT))
+        disk_initialize();
+
+    //Return the card type
+    return m_CardType;
+}
+
+int SDFileSystem::disk_initialize()
+{
+    char resp;
+
+    //Make sure there's a card in the socket before proceeding
+    checkSocket();
+    if (m_Status & STA_NODISK)
+        return m_Status;
+
+    //Make sure we're not already initialized before proceeding
+    if (!(m_Status & STA_NOINIT))
+        return m_Status;
+
+    //Set the SPI frequency to 100kHz for initialization
+    m_SPI.frequency(100000);
+
+    //Send 80 dummy clocks with /CS and DI held high
+    m_CS = 1;
+    for (int i = 0; i < 10; i++)
+        m_SPI.write(0xFF);
+
+    //Write CMD0(0), and check for a valid response
+    resp = writeCommand(CMD0, 0);
+    if (resp != 0x01) {
+        //Initialization failed
+        m_CardType = CARD_UNKNOWN;
+        return m_Status;
+    }
+
+    //Write CMD8(0x000001AA) to see if this is an SDCv2 card
+    resp = writeCommand(CMD8, 0x000001AA);
+    if (resp == 0x01) {
+        //This is an SDCv2 card, get the 32-bit return value and verify the voltage range/check pattern
+        if ((readReturn() & 0xFFF) != 0x1AA) {
+            //Initialization failed
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+
+        //Send CMD58(0) to read the OCR, and verify that the card supports 3.2-3.3V
+        resp = writeCommand(CMD58, 0);
+        if (resp != 0x01 || !(readReturn() & (1 << 20))) {
+            //Initialization failed
+            deselect();
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+
+        //Send ACMD41(0x40100000) repeatedly for up to 1 second to initialize the card
+        for (int i = 0; i < 1000; i++) {
+            resp = writeCommand(ACMD41, 0x40100000);
+            if (resp != 0x01)
+                break;
+            wait_ms(1);
+        }
+
+        //Check if the card initialized
+        if (resp != 0x00) {
+            //Initialization failed
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+
+        //Send CMD58(0) to read the OCR
+        resp = writeCommand(CMD58, 0);
+        if (resp == 0x00) {
+            //Check the CCS bit to determine if this is a high capacity card
+            if (readReturn() & 0x40000000)
+                m_CardType = CARD_SDHC;
+            else
+                m_CardType = CARD_SD;
+        } else {
+            //Initialization failed
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+    } else {
+        //Didn't respond or illegal command, this is either an SDCv1 or MMC card
+        deselect();
+
+        //Send CMD58(0) to read the OCR, and verify that the card supports 3.2-3.3V
+        resp = writeCommand(CMD58, 0);
+        if (resp != 0x01 || !(readReturn() & (1 << 20))) {
+            //Initialization failed
+            deselect();
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+
+        //Try to initialize the card using ACMD41(0x00100000) for 1 second
+        for (int i = 0; i < 1000; i++) {
+            resp = writeCommand(ACMD41, 0x00100000);
+            if (resp != 0x01)
+                break;
+            wait_ms(1);
+        }
+
+        //Check if the card initialized
+        if (resp == 0x00) {
+            //This is an SDCv1 standard capacity card
+            m_CardType = CARD_SD;
+        } else {
+            //Try to initialize the card using CMD1(0x00100000) for 1 second
+            for (int i = 0; i < 1000; i++) {
+                resp = writeCommand(CMD1, 0x00100000);
+                if (resp != 0x01)
+                    break;
+                wait_ms(1);
+            }
+
+            //Check if the card initialized
+            if (resp == 0x00) {
+                //This is an MMCv3 card
+                m_CardType = CARD_MMC;
+            } else {
+                //Initialization failed
+                m_CardType = CARD_UNKNOWN;
+                return m_Status;
+            }
+        }
+    }
+
+    //Send CMD59(0x00000001) to re-enable CRC
+    resp = writeCommand(CMD59, 0x00000001);
+    if (resp != 0x00) {
+        //Initialization failed
+        m_CardType = CARD_UNKNOWN;
+        return m_Status;
+    }
+
+    //Send CMD16(0x00000200) to force the block size to 512B if necessary
+    if (m_CardType != CARD_SDHC) {
+        resp = writeCommand(CMD16, 0x00000200);
+        if (resp != 0x00) {
+            //Initialization failed
+            m_CardType = CARD_UNKNOWN;
+            return m_Status;
+        }
+    }
+
+    //The card is now initialized
+    m_Status &= ~STA_NOINIT;
+
+    //Increase the SPI frequency to full speed (limited to 20MHz for MMC, or 25MHz for SDC)
+    if (m_CardType == CARD_MMC && m_SpiFreq > 20000000)
+        m_SPI.frequency(20000000);
+    else if (m_SpiFreq > 25000000)
+        m_SPI.frequency(25000000);
+    else
+        m_SPI.frequency(m_SpiFreq);
+
+    //Return the device status
+    return m_Status;
+}
+
+int SDFileSystem::disk_status()
+{
+    //Check if there's a card in the socket
+    checkSocket();
+
+    //Return the device status
+    return m_Status;
+}
+
+int SDFileSystem::disk_read(uint8_t* buffer, uint64_t sector)
+{
+    //Make sure the device is initialized before proceeding
+    if (m_Status & STA_NOINIT)
+        return RES_NOTRDY;
+
+    //Convert from LBA to a byte address for standard capacity cards
+    if (m_CardType != CARD_SDHC)
+        sector *= 512;
+
+    //Try to read the block up to 3 times
+    for (int i = 0; i < 3; i++) {
+        //Send CMD17(sector) to read a single block
+        char resp = writeCommand(CMD17, sector);
+        if (resp == 0x00) {
+            //Try to read the sector, and return if successful
+            if (readData((char*)buffer, 512))
+                return RES_OK;
+        } else {
+            //The command failed
+            deselect();
+            return RES_ERROR;
+        }
+    }
+
+    //The read operation failed 3 times (CRC most likely)
+    return RES_ERROR;
+}
+
+int SDFileSystem::disk_write(const uint8_t* buffer, uint64_t sector)
+{
+    //Make sure the device is initialized before proceeding
+    if (m_Status & STA_NOINIT)
+        return RES_NOTRDY;
+
+    //Make sure the device isn't write protected before proceeding
+    if (m_Status & STA_PROTECT)
+        return RES_WRPRT;
+
+    //Convert from LBA to a byte address for older cards
+    if (m_CardType != CARD_SDHC)
+        sector *= 512;
+
+    //Try to write the block up to 3 times
+    for (int i = 0; i < 3; i++) {
+        //Send CMD24(sector) to write a single block
+        if (writeCommand(CMD24, sector) == 0x00) {
+            //Wait for up to 500ms for the card to become ready
+            if (!waitReady(500)) {
+                //We timed out
+                deselect();
+                continue;
+            }
+
+            //Send the write data token
+            m_SPI.write(0xFE);
+
+            //Write the data block from the buffer
+            for (int b = 0; b < 512; b++)
+                m_SPI.write(buffer[b]);
+
+            //Calculate the CRC16 checksum for the data block and send it
+            unsigned short crc = CRC16((char*)buffer, 512);
+            m_SPI.write(crc >> 8);
+            m_SPI.write(crc);
+
+            //Receive the data response, and deselect the card
+            char resp = m_SPI.write(0xFF) & 0x1F;
+            deselect();
+
+            //Check the response
+            if (resp == 0x05)
+                return RES_OK;
+            else if (resp == 0x0D)
+                return RES_ERROR;
+        } else {
+            //The command failed
+            deselect();
+            return RES_ERROR;
+        }
+    }
+
+    //The operation either timed out 3 times, failed the CRC check 3 times, or experienced a write error
+    return RES_ERROR;
+}
+
+int SDFileSystem::disk_sync()
+{
+    //Select the card so we're forced to wait for the end of any internal write processes
+    bool ret = select();
+    deselect();
+
+    //Return success/failure
+    return (ret) ? RES_OK : RES_ERROR;
+}
+
+uint64_t SDFileSystem::disk_sectors()
+{
+    //Make sure the device is initialized before proceeding
+    if (m_Status & STA_NOINIT)
+        return 0;
+
+    //Try to read the CSD register up to 3 times
+    for (int i = 0; i < 3; i++) {
+        //Send CMD9(0) to read the CSD register
+        if (writeCommand(CMD9, 0) == 0x00) {
+            //Receive the 16B CSD data
+            char csd[16];
+            if (readData(csd, 16)) {
+                //Calculate the sector count based on the card type
+                if ((csd[0] >> 6) == 0x01) {
+                    //Calculate the sector count a high capacity card
+                    uint64_t sectors = (((csd[7] & 0x3F) << 16) | (csd[8] << 8) | csd[9]) + 1;
+                    return sectors << 10;
+                } else {
+                    //Calculate the sector count standard capacity card
+                    uint64_t sectors = (((csd[6] & 0x03) << 10) | (csd[7] << 2) | ((csd[8] & 0xC0) >> 6)) + 1;
+                    sectors <<= ((((csd[9] & 0x03) << 1) | ((csd[10] & 0x80) >> 7)) + 2);
+                    sectors <<= (csd[5] & 0x0F);
+                    return sectors >> 9;
+                }
+            }
+        } else {
+            //The command failed
+            deselect();
+            return 0;
+        }
+    }
+
+    //The read operation failed 3 times (CRC most likely)
+    return 0;
+}
+
+void SDFileSystem::checkSocket()
+{
+    //Check if a card is in the socket
+    if (m_CD) {
+        //The socket is occupied, clear the STA_NODISK flag
+        m_Status &= ~STA_NODISK;
+    } else {
+        //The socket is empty
+        m_Status |= (STA_NODISK | STA_NOINIT);
+        m_CardType = CARD_NONE;
+    }
+}
+
+inline bool SDFileSystem::waitReady(int timeout)
+{
+    //Wait for the specified timeout for the card to become ready
+    for (int i = 0; i < timeout; i++) {
+        if (m_SPI.write(0xFF) == 0xFF)
+            return true;
+        wait_ms(1);
+    }
+
+    //We timed out
+    return false;
+}
+
+inline bool SDFileSystem::select()
+{
+    //Pull /CS low
+    m_CS = 0;
+
+    //Send a dummy clock to enable DO
+    m_SPI.write(0xFF);
+
+    //Wait for up to 500ms for the card to become ready
+    if (waitReady(500))
+        return true;
+
+    //We timed out, deselect and return false
+    deselect();
+    return false;
+}
+
+inline void SDFileSystem::deselect()
+{
+    //Pull /CS high
+    m_CS = 1;
+
+    //Send a dummy byte to release DO
+    m_SPI.write(0xFF);
+}
+
+char SDFileSystem::writeCommand(char cmd, unsigned int arg)
+{
+    char resp;
+
+    //Try to send the command up to 3 times
+    for (int i = 0; i < 3; i++) {
+        //Send a CMD55 prior to an ACMD
+        if (cmd == ACMD41) {
+            resp = writeCommand(CMD55, 0);
+            if (resp > 0x01)
+                return resp;
+        }
+
+        //Select the card and wait for ready
+        if (!select())
+            return 0xFF;
+
+        //Prepare the command packet
+        char cmdPacket[6];
+        cmdPacket[0] = 0x40 | cmd;
+        cmdPacket[1] = arg >> 24;
+        cmdPacket[2] = arg >> 16;
+        cmdPacket[3] = arg >> 8;
+        cmdPacket[4] = arg;
+        cmdPacket[5] = (CRC7(cmdPacket, 5) << 1) | 0x01;
+
+        //Send the command packet
+        for (int b = 0; b < 6; b++)
+            m_SPI.write(cmdPacket[b]);
+
+        //Allow up to 10 bytes of delay for the command response
+        for (int b = 0; b < 10; b++) {
+            resp = m_SPI.write(0xFF);
+            if (!(resp & 0x80))
+                break;
+        }
+
+        //Deselect the card unless there's more data to read/write
+        if (resp == 0xFF || (resp & (1 << 3)) || !(cmd == CMD8 || cmd == CMD9 || cmd == CMD17 || cmd == CMD24 || cmd == CMD55 || cmd == CMD58))
+            deselect();
+
+        //Return the response if there were no CRC errors
+        if (resp == 0xFF || !(resp & (1 << 3)))
+            return resp;
+    }
+
+    //The command failed 3 times due to CRC errors
+    return 0xFF;
+}
+
+unsigned int SDFileSystem::readReturn()
+{
+    unsigned int ret;
+
+    //Read the 32-bit response value
+    ret = (m_SPI.write(0xFF) << 24);
+    ret |= (m_SPI.write(0xFF) << 16);
+    ret |= (m_SPI.write(0xFF) << 8);
+    ret |= m_SPI.write(0xFF);
+
+    //Deselect the card
+    deselect();
+
+    //Return the response value
+    return ret;
+}
+
+bool SDFileSystem::readData(char* buffer, int length)
+{
+    char token;
+
+    //Wait for up to 200ms for the DataStart token to arrive
+    for (int i = 0; i < 200; i++) {
+        token = m_SPI.write(0xFF);
+        if (token != 0xFF)
+            break;
+        wait_ms(1);
+    }
+
+    //Make sure the token is valid
+    if (token != 0xFE)
+        return false;
+
+    //Read the data into the buffer
+    for (int i = 0; i < length; i++)
+        buffer[i] = m_SPI.write(0xFF);
+
+    //Read the CRC16 checksum for the data block, and deselect the card
+    unsigned short crc = (m_SPI.write(0xFF) << 8);
+    crc |= m_SPI.write(0xFF);
+    deselect();
+
+    //Indicate whether the CRC16 checksum was valid or not
+    if (crc == CRC16(buffer, length))
+        return true;
+    else
+        return false;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SDFileSystem.h	Tue Jul 29 20:12:23 2014 +0000
@@ -0,0 +1,136 @@
+/* SD/MMC File System Library
+ * Copyright (c) 2014 Neil Thiessen
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SD_FILE_SYSTEM_H
+#define SD_FILE_SYSTEM_H
+
+#include "mbed.h"
+#include "FATFileSystem.h"
+#include <stdint.h>
+
+/** SDFileSystem class.
+ *  Used for creating a virtual file system for accessing SD/MMC cards via SPI.
+ *
+ * Example:
+ * @code
+ * #include "mbed.h"
+ * #include "SDFileSystem.h"
+ *
+ * //Create an SDFileSystem object
+ * SDFileSystem sd(p5, p6, p7, p19, p20, "sd")
+ *
+ * int main()
+ * {
+ *     //Perform a write test
+ *     printf("\nWriting to SD card...");
+ *     FILE *fp = fopen("/sd/sdtest.txt", "w");
+ *     if (fp != NULL) {
+ *         fprintf(fp, "We're writing to an SD card!");
+ *         fclose(fp);
+ *         printf("success!\n");
+ *     } else {
+ *         printf("failed!\n");
+ *     }
+ *
+ *     //Perform a read test
+ *     printf("Reading from SD card...");
+ *     fp = fopen("/sd/sdtest.txt", "r");
+ *     if (fp != NULL) {
+ *         char c = fgetc(fp);
+ *         if (c == 'W')
+ *             printf("success!\n");
+ *         else
+ *             printf("incorrect char (%c)!\n", c);
+ *         fclose(fp);
+ *     } else {
+ *         printf("failed!\n");
+ *     }
+ * }
+ * @endcode
+ */
+class SDFileSystem : public FATFileSystem
+{
+public:
+    /** Represents the different SD/MMC card types
+     */
+    enum CardType {
+        CARD_NONE,      /**< No card is present */
+        CARD_MMC,       /**< MMC card */
+        CARD_SD,        /**< Standard capacity SD card */
+        CARD_SDHC,      /**< High capacity SD card */
+        CARD_UNKNOWN    /**< Unknown or unsupported card */
+    };
+
+    /** Create a virtual file system for accessing SD/MMC cards via SPI
+     *
+     * @param mosi The SPI data out pin.
+     * @param miso The SPI data in pin.
+     * @param sclk The SPI clock pin.
+     * @param cs The SPI chip select pin.
+     * @param cd The active-high card detect pin.
+     * @param name The name used to access the virtual filesystem.
+     * @param hz The SPI bus frequency (defaults to 1MHz).
+     */
+    SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, PinName cd, const char* name, int hz = 1000000);
+
+    /** Get the detected SD/MMC card type
+     *
+     * @returns The detected card type as a CardType enum.
+     */
+    SDFileSystem::CardType card_type();
+
+    virtual int disk_initialize();
+    virtual int disk_status();
+    virtual int disk_read(uint8_t* buffer, uint64_t sector);
+    virtual int disk_write(const uint8_t* buffer, uint64_t sector);
+    virtual int disk_sync();
+    virtual uint64_t disk_sectors();
+
+private:
+    //Commands
+    enum Command {
+        CMD0 = 0,       /**< GO_IDLE_STATE */
+        CMD1 = 1,       /**< SEND_OP_COND */
+        ACMD41 = 41,    /**< APP_SEND_OP_COND */
+        CMD8 = 8,       /**< SEND_IF_COND */
+        CMD9 = 9,       /**< SEND_CSD */
+        CMD16 = 16,     /**< SET_BLOCKLEN */
+        CMD17 = 17,     /**< READ_SINGLE_BLOCK */
+        CMD24 = 24,     /**< WRITE_BLOCK */
+        CMD55 = 55,     /**< APP_CMD */
+        CMD58 = 58,     /**< READ_OCR */
+        CMD59 = 59      /**< CRC_ON_OFF */
+    };
+
+    //Member variables
+    SPI m_SPI;
+    DigitalOut m_CS;
+    InterruptIn m_CD;
+    int m_SpiFreq;
+    int m_Status;
+    SDFileSystem::CardType m_CardType;
+
+    //Internal methods
+    void checkSocket();
+    bool waitReady(int timeout);
+    bool select();
+    void deselect();
+    char writeCommand(char cmd, unsigned int arg);
+    unsigned int readReturn();
+    bool readData(char* buffer, int length);
+};
+
+#endif