Revision 0:ad67c66b2e84, committed 2020-02-07

Comitter:

perlatecnica

Date:

Fri Feb 07 07:25:23 2020 +0000

Commit message:

v1.0

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SDBlockDevice/SDBlockDevice.cpp	Fri Feb 07 07:25:23 2020 +0000
@@ -0,0 +1,672 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2012 ARM Limited
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+/* Introduction
+ * ------------
+ * SD and MMC cards support a number of interfaces, but common to them all
+ * is one based on SPI. This is the one I'm implmenting because it means
+ * it is much more portable even though not so performant, and we already
+ * have the mbed SPI Interface!
+ *
+ * The main reference I'm using is Chapter 7, "SPI Mode" of:
+ *  http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
+ *
+ * SPI Startup
+ * -----------
+ * The SD card powers up in SD mode. The start-up procedure is complicated
+ * by the requirement to support older SDCards in a backwards compatible
+ * way with the new higher capacity variants SDHC and SDHC.
+ *
+ * The following figures from the specification with associated text describe
+ * the SPI mode initialisation process:
+ *  - Figure 7-1: SD Memory Card State Diagram (SPI mode)
+ *  - Figure 7-2: SPI Mode Initialization Flow
+ *
+ * Firstly, a low initial clock should be selected (in the range of 100-
+ * 400kHZ). After initialisation has been completed, the switch to a
+ * higher clock speed can be made (e.g. 1MHz). Newer cards will support
+ * higher speeds than the default _transfer_sck defined here.
+ *
+ * Next, note the following from the SDCard specification (note to
+ * Figure 7-1):
+ *
+ *  In any of the cases CMD1 is not recommended because it may be difficult for the host
+ *  to distinguish between MultiMediaCard and SD Memory Card
+ *
+ * Hence CMD1 is not used for the initialisation sequence.
+ *
+ * The SPI interface mode is selected by asserting CS low and sending the
+ * reset command (CMD0). The card will respond with a (R1) response.
+ * In practice many cards initially respond with 0xff or invalid data
+ * which is ignored. Data is read until a valid response is received
+ * or the number of re-reads has exceeded a maximim count. If a valid
+ * response is not received then the CMD0 can be retried. This
+ * has been found to successfully initialise cards where the SPI master
+ * (on MCU) has been reset but the SDCard has not, so the first
+ * CMD0 may be lost.
+ *
+ * CMD8 is optionally sent to determine the voltage range supported, and
+ * indirectly determine whether it is a version 1.x SD/non-SD card or
+ * version 2.x. I'll just ignore this for now.
+ *
+ * ACMD41 is repeatedly issued to initialise the card, until "in idle"
+ * (bit 0) of the R1 response goes to '0', indicating it is initialised.
+ *
+ * You should also indicate whether the host supports High Capicity cards,
+ * and check whether the card is high capacity - i'll also ignore this
+ *
+ * SPI Protocol
+ * ------------
+ * The SD SPI protocol is based on transactions made up of 8-bit words, with
+ * the host starting every bus transaction by asserting the CS signal low. The
+ * card always responds to commands, data blocks and errors.
+ *
+ * The protocol supports a CRC, but by default it is off (except for the
+ * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
+ * I'll leave the CRC off I think!
+ *
+ * Standard capacity cards have variable data block sizes, whereas High
+ * Capacity cards fix the size of data block to 512 bytes. I'll therefore
+ * just always use the Standard Capacity cards with a block size of 512 bytes.
+ * This is set with CMD16.
+ *
+ * You can read and write single blocks (CMD17, CMD25) or multiple blocks
+ * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
+ * the card gets a read command, it responds with a response token, and then
+ * a data token or an error.
+ *
+ * SPI Command Format
+ * ------------------
+ * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
+ *
+ * +---------------+------------+------------+-----------+----------+--------------+
+ * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
+ * +---------------+------------+------------+-----------+----------+--------------+
+ *
+ * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
+ *
+ * All Application Specific commands shall be preceded with APP_CMD (CMD55).
+ *
+ * SPI Response Format
+ * -------------------
+ * The main response format (R1) is a status byte (normally zero). Key flags:
+ *  idle - 1 if the card is in an idle state/initialising
+ *  cmd  - 1 if an illegal command code was detected
+ *
+ *    +-------------------------------------------------+
+ * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
+ *    +-------------------------------------------------+
+ *
+ * R1b is the same, except it is followed by a busy signal (zeros) until
+ * the first non-zero byte when it is ready again.
+ *
+ * Data Response Token
+ * -------------------
+ * Every data block written to the card is acknowledged by a byte
+ * response token
+ *
+ * +----------------------+
+ * | xxx | 0 | status | 1 |
+ * +----------------------+
+ *              010 - OK!
+ *              101 - CRC Error
+ *              110 - Write Error
+ *
+ * Single Block Read and Write
+ * ---------------------------
+ *
+ * Block transfers have a byte header, followed by the data, followed
+ * by a 16-bit CRC. In our case, the data will always be 512 bytes.
+ *
+ * +------+---------+---------+- -  - -+---------+-----------+----------+
+ * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
+ * +------+---------+---------+- -  - -+---------+-----------+----------+
+ */
+
+/* If the target has no SPI support then SDCard is not supported */
+#ifdef DEVICE_SPI
+
+#include "SDBlockDevice.h"
+#include "mbed_debug.h"
+
+#define SD_COMMAND_TIMEOUT                       5000    /*!< Number of times to query card for correct result */
+#define SD_CMD0_GO_IDLE_STATE_RETRIES            3       /*!< Number of retries for sending CMDO*/
+#define SD_CMD0_GO_IDLE_STATE                    0x00    /*!< CMD0 code value */
+#define SD_CMD0_INVALID_RESPONSE_TIMEOUT         -1      /*!< CMD0 received invalid responses and timed out */
+#define SD_DBG                                   0
+
+#define SD_BLOCK_DEVICE_ERROR_WOULD_BLOCK        -5001	/*!< operation would block */
+#define SD_BLOCK_DEVICE_ERROR_UNSUPPORTED        -5002	/*!< unsupported operation */
+#define SD_BLOCK_DEVICE_ERROR_PARAMETER          -5003	/*!< invalid parameter */
+#define SD_BLOCK_DEVICE_ERROR_NO_INIT            -5004	/*!< uninitialized */
+#define SD_BLOCK_DEVICE_ERROR_NO_DEVICE          -5005	/*!< device is missing or not connected */
+#define SD_BLOCK_DEVICE_ERROR_WRITE_PROTECTED    -5006	/*!< write protected */
+
+
+SDBlockDevice::SDBlockDevice(PinName mosi, PinName miso, PinName sclk, PinName cs)
+    : _spi(mosi, miso, sclk), _cs(cs), _is_initialized(0)
+{
+    _cs = 1;
+
+    // Set default to 100kHz for initialisation and 1MHz for data transfer
+    _init_sck = 100000;
+    _transfer_sck = 1000000;
+}
+
+SDBlockDevice::~SDBlockDevice()
+{
+    if (_is_initialized) {
+        deinit();
+    }
+}
+
+#define R1_IDLE_STATE           (1 << 0)
+#define R1_ERASE_RESET          (1 << 1)
+#define R1_ILLEGAL_COMMAND      (1 << 2)
+#define R1_COM_CRC_ERROR        (1 << 3)
+#define R1_ERASE_SEQUENCE_ERROR (1 << 4)
+#define R1_ADDRESS_ERROR        (1 << 5)
+#define R1_PARAMETER_ERROR      (1 << 6)
+
+// Types
+//  - v1.x Standard Capacity
+//  - v2.x Standard Capacity
+//  - v2.x High Capacity
+//  - Not recognised as an SD Card
+#define SDCARD_FAIL 0
+#define SDCARD_V1   1
+#define SDCARD_V2   2
+#define SDCARD_V2HC 3
+
+int SDBlockDevice::_initialise_card()
+{
+    _dbg = SD_DBG;
+    // Set to SCK for initialisation, and clock card with cs = 1
+    _spi.lock();
+    _spi.frequency(_init_sck);
+    _cs = 1;
+    for (int i = 0; i < 16; i++) {
+        _spi.write(0xFF);
+    }
+    _spi.unlock();
+
+    /* Transition from SD Card mode to SPI mode by sending CMD0 GO_IDLE_STATE command */
+    if (_go_idle_state() != R1_IDLE_STATE) {
+        debug_if(_dbg, "No disk, or could not put SD card in to SPI idle state\n");
+        return SD_BLOCK_DEVICE_ERROR_NO_DEVICE;
+    }
+
+    // send CMD8 to determine whether it is ver 2.x
+    int r = _cmd8();
+    if (r == R1_IDLE_STATE) {
+        return _initialise_card_v2();
+    } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
+        return _initialise_card_v1();
+    } else {
+        debug_if(_dbg, "Not in idle state after sending CMD8 (not an SD card?)\n");
+        return BD_ERROR_DEVICE_ERROR;
+    }
+}
+
+int SDBlockDevice::_initialise_card_v1()
+{
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        _cmd(55, 0);
+        if (_cmd(41, 0) == 0) {
+            _block_size = 512;
+            debug_if(_dbg, "\n\rInit: SEDCARD_V1\n\r");
+            return BD_ERROR_OK;
+        }
+    }
+
+    debug_if(_dbg, "Timeout waiting for v1.x card\n");
+    return BD_ERROR_DEVICE_ERROR;
+}
+
+int SDBlockDevice::_initialise_card_v2()
+{
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        wait_ms(50);
+        _cmd58();
+        _cmd(55, 0);
+        if (_cmd(41, 0x40000000) == 0) {
+            _cmd58();
+            debug_if(_dbg, "\n\rInit: SDCARD_V2\n\r");
+            _block_size = 1;
+            return BD_ERROR_OK;
+        }
+    }
+
+    debug_if(_dbg, "Timeout waiting for v2.x card\n");
+    return BD_ERROR_DEVICE_ERROR;
+}
+
+int SDBlockDevice::init()
+{
+    _lock.lock();
+    int err = _initialise_card();
+    _is_initialized = (err == BD_ERROR_OK);
+    if (!_is_initialized) {
+        debug_if(_dbg, "Fail to initialize card\n");
+        _lock.unlock();
+        return err;
+    }
+    debug_if(_dbg, "init card = %d\n", _is_initialized);
+    _sectors = _sd_sectors();
+
+    // Set block length to 512 (CMD16)
+    if (_cmd(16, 512) != 0) {
+        debug_if(_dbg, "Set 512-byte block timed out\n");
+        _lock.unlock();
+        return BD_ERROR_DEVICE_ERROR;
+    }
+
+    // Set SCK for data transfer
+    _spi.frequency(_transfer_sck);
+    _lock.unlock();
+    return BD_ERROR_OK;
+}
+
+int SDBlockDevice::deinit()
+{
+    return 0;
+}
+
+int SDBlockDevice::program(const void *b, bd_addr_t addr, bd_size_t size)
+{
+    if (!is_valid_program(addr, size)) {
+        return SD_BLOCK_DEVICE_ERROR_PARAMETER;
+    }
+
+    _lock.lock();
+    if (!_is_initialized) {
+        _lock.unlock();
+        return SD_BLOCK_DEVICE_ERROR_NO_INIT;
+    }
+
+    const uint8_t *buffer = static_cast<const uint8_t*>(b);
+    while (size > 0) {
+        bd_addr_t block = addr / 512;
+        // set write address for single block (CMD24)
+        if (_cmd(24, block * _block_size) != 0) {
+            _lock.unlock();
+            return BD_ERROR_DEVICE_ERROR;
+        }
+
+        // send the data block
+        _write(buffer, 512);
+        buffer += 512;
+        addr += 512;
+        size -= 512;
+    }
+    _lock.unlock();
+    return 0;
+}
+
+int SDBlockDevice::read(void *b, bd_addr_t addr, bd_size_t size)
+{
+    if (!is_valid_read(addr, size)) {
+        return SD_BLOCK_DEVICE_ERROR_PARAMETER;
+    }
+
+    _lock.lock();
+    if (!_is_initialized) {
+        _lock.unlock();
+        return SD_BLOCK_DEVICE_ERROR_PARAMETER;
+    }
+    
+    uint8_t *buffer = static_cast<uint8_t *>(b);
+    while (size > 0) {
+        bd_addr_t block = addr / 512;
+        // set read address for single block (CMD17)
+        if (_cmd(17, block * _block_size) != 0) {
+            _lock.unlock();
+            return BD_ERROR_DEVICE_ERROR;
+        }
+        
+        // receive the data
+        _read(buffer, 512);
+        buffer += 512;
+        addr += 512;
+        size -= 512;
+    }
+    _lock.unlock();
+    return 0;
+}
+
+int SDBlockDevice::erase(bd_addr_t addr, bd_size_t size)
+{
+    return 0;
+}
+
+bd_size_t SDBlockDevice::get_read_size() const
+{
+    return 512;
+}
+
+bd_size_t SDBlockDevice::get_program_size() const
+{
+    return 512;
+}
+
+bd_size_t SDBlockDevice::get_erase_size() const
+{
+    return 512;
+}
+
+bd_size_t SDBlockDevice::size() const
+{
+    bd_size_t sectors = 0;
+    _lock.lock();
+    if(_is_initialized) {
+    	sectors = _sectors;
+    }
+    _lock.unlock();
+    return 512*sectors;
+}
+
+void SDBlockDevice::debug(bool dbg)
+{
+    _dbg = dbg;
+}
+
+
+// PRIVATE FUNCTIONS
+int SDBlockDevice::_cmd(int cmd, int arg) {
+    _spi.lock();
+    _cs = 0;
+
+    // send a command
+    _spi.write(0x40 | cmd);
+    _spi.write(arg >> 24);
+    _spi.write(arg >> 16);
+    _spi.write(arg >> 8);
+    _spi.write(arg >> 0);
+    _spi.write(0x95);
+
+    // wait for the response (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        int response = _spi.write(0xFF);
+        if (!(response & 0x80)) {
+            _cs = 1;
+            _spi.write(0xFF);
+            _spi.unlock();
+            return response;
+        }
+    }
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return -1; // timeout
+}
+int SDBlockDevice::_cmdx(int cmd, int arg) {
+    _spi.lock();
+    _cs = 0;
+
+    // send a command
+    _spi.write(0x40 | cmd);
+    _spi.write(arg >> 24);
+    _spi.write(arg >> 16);
+    _spi.write(arg >> 8);
+    _spi.write(arg >> 0);
+    _spi.write(0x95);
+
+    // wait for the response (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        int response = _spi.write(0xFF);
+        if (!(response & 0x80)) {
+            _cs = 1;
+            _spi.unlock();
+            return response;
+        }
+    }
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return -1; // timeout
+}
+
+
+int SDBlockDevice::_cmd58() {
+    _spi.lock();
+    _cs = 0;
+    int arg = 0;
+
+    // send a command
+    _spi.write(0x40 | 58);
+    _spi.write(arg >> 24);
+    _spi.write(arg >> 16);
+    _spi.write(arg >> 8);
+    _spi.write(arg >> 0);
+    _spi.write(0x95);
+
+    // wait for the response (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+        int response = _spi.write(0xFF);
+        if (!(response & 0x80)) {
+            int ocr = _spi.write(0xFF) << 24;
+            ocr |= _spi.write(0xFF) << 16;
+            ocr |= _spi.write(0xFF) << 8;
+            ocr |= _spi.write(0xFF) << 0;
+            _cs = 1;
+            _spi.write(0xFF);
+            _spi.unlock();
+            return response;
+        }
+    }
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return -1; // timeout
+}
+
+int SDBlockDevice::_cmd8() {
+    _spi.lock();
+    _cs = 0;
+
+    // send a command
+    _spi.write(0x40 | 8); // CMD8
+    _spi.write(0x00);     // reserved
+    _spi.write(0x00);     // reserved
+    _spi.write(0x01);     // 3.3v
+    _spi.write(0xAA);     // check pattern
+    _spi.write(0x87);     // crc
+
+    // wait for the response (response[7] == 0)
+    for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
+        char response[5];
+        response[0] = _spi.write(0xFF);
+        if (!(response[0] & 0x80)) {
+            for (int j = 1; j < 5; j++) {
+                response[i] = _spi.write(0xFF);
+            }
+            _cs = 1;
+            _spi.write(0xFF);
+            _spi.unlock();
+            return response[0];
+        }
+    }
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return -1; // timeout
+}
+
+int SDBlockDevice::_go_idle_state() {
+    _spi.lock();
+    _cs = 0;
+    int cmd_arg = 0;    /* CMD0 argument is just "stuff bits" */
+    int ret = SD_CMD0_INVALID_RESPONSE_TIMEOUT;
+
+    /* Reseting the MCU SPI master may not reset the on-board SDCard, in which
+     * case when MCU power-on occurs the SDCard will resume operations as
+     * though there was no reset. In this scenario the first CMD0 will
+     * not be interpreted as a command and get lost. For some cards retrying
+     * the command overcomes this situation. */
+    for (int num_retries = 0; ret != R1_IDLE_STATE && (num_retries < SD_CMD0_GO_IDLE_STATE_RETRIES); num_retries++) {
+        /* send a CMD0 */
+        _spi.write(0x40 | SD_CMD0_GO_IDLE_STATE);
+        _spi.write(cmd_arg >> 24);
+        _spi.write(cmd_arg >> 16);
+        _spi.write(cmd_arg >> 8);
+        _spi.write(cmd_arg >> 0);
+        _spi.write(0x95);
+
+        /* wait for the R1_IDLE_STATE response */
+        for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
+            int response = _spi.write(0xFF);
+            /* Explicitly check for the R1_IDLE_STATE response rather that most significant bit
+             * being 0 because invalid data can be returned. */
+            if ((response == R1_IDLE_STATE)) {
+                ret = response;
+                break;
+            }
+            wait_ms(1);
+        }
+    }
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return ret;
+}
+
+int SDBlockDevice::_read(uint8_t *buffer, uint32_t length) {
+    _spi.lock();
+    _cs = 0;
+
+    // read until start byte (0xFF)
+    while (_spi.write(0xFF) != 0xFE);
+
+    // read data
+    for (uint32_t i = 0; i < length; i++) {
+        buffer[i] = _spi.write(0xFF);
+    }
+    _spi.write(0xFF); // checksum
+    _spi.write(0xFF);
+
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return 0;
+}
+
+int SDBlockDevice::_write(const uint8_t*buffer, uint32_t length) {
+    _spi.lock();
+    _cs = 0;
+
+    // indicate start of block
+    _spi.write(0xFE);
+
+    // write the data
+    for (uint32_t i = 0; i < length; i++) {
+        _spi.write(buffer[i]);
+    }
+
+    // write the checksum
+    _spi.write(0xFF);
+    _spi.write(0xFF);
+
+    // check the response token
+    if ((_spi.write(0xFF) & 0x1F) != 0x05) {
+        _cs = 1;
+        _spi.write(0xFF);
+        _spi.unlock();
+        return 1;
+    }
+
+    // wait for write to finish
+    while (_spi.write(0xFF) == 0);
+
+    _cs = 1;
+    _spi.write(0xFF);
+    _spi.unlock();
+    return 0;
+}
+
+static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
+    uint32_t bits = 0;
+    uint32_t size = 1 + msb - lsb;
+    for (uint32_t i = 0; i < size; i++) {
+        uint32_t position = lsb + i;
+        uint32_t byte = 15 - (position >> 3);
+        uint32_t bit = position & 0x7;
+        uint32_t value = (data[byte] >> bit) & 1;
+        bits |= value << i;
+    }
+    return bits;
+}
+
+uint32_t SDBlockDevice::_sd_sectors() {
+    uint32_t c_size, c_size_mult, read_bl_len;
+    uint32_t block_len, mult, blocknr, capacity;
+    uint32_t hc_c_size;
+    uint32_t blocks;
+
+    // CMD9, Response R2 (R1 byte + 16-byte block read)
+    if (_cmdx(9, 0) != 0) {
+        debug_if(_dbg, "Didn't get a response from the disk\n");
+        return 0;
+    }
+
+    uint8_t csd[16];
+    if (_read(csd, 16) != 0) {
+        debug_if(_dbg, "Couldn't read csd response from disk\n");
+        return 0;
+    }
+
+    // csd_structure : csd[127:126]
+    // c_size        : csd[73:62]
+    // c_size_mult   : csd[49:47]
+    // read_bl_len   : csd[83:80] - the *maximum* read block length
+
+    int csd_structure = ext_bits(csd, 127, 126);
+
+    switch (csd_structure) {
+        case 0:
+            _block_size = 512;
+            c_size = ext_bits(csd, 73, 62);
+            c_size_mult = ext_bits(csd, 49, 47);
+            read_bl_len = ext_bits(csd, 83, 80);
+
+            block_len = 1 << read_bl_len;
+            mult = 1 << (c_size_mult + 2);
+            blocknr = (c_size + 1) * mult;
+            capacity = blocknr * block_len;
+            blocks = capacity / 512;
+            debug_if(_dbg, "\n\rSDBlockDevice\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
+            break;
+
+        case 1:
+            _block_size = 1;
+            hc_c_size = ext_bits(csd, 63, 48);
+            blocks = (hc_c_size+1)*1024;
+            debug_if(_dbg, "\n\rSDHC Card \n\rhc_c_size: %d\n\rcapacity: %lld \n\rsectors: %lld\n\r", hc_c_size, blocks*512, blocks);
+            break;
+
+        default:
+            debug_if(_dbg, "CSD struct unsupported\r\n");
+            return 0;
+    };
+    return blocks;
+}
+
+#endif  /* DEVICE_SPI */
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SDBlockDevice/SDBlockDevice.h	Fri Feb 07 07:25:23 2020 +0000
@@ -0,0 +1,172 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2012 ARM Limited
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef MBED_SD_BLOCK_DEVICE_H
+#define MBED_SD_BLOCK_DEVICE_H
+
+/* If the target has no SPI support then SDCard is not supported */
+#ifdef DEVICE_SPI
+
+#include "BlockDevice.h"
+#include "mbed.h"
+
+
+/** Access an SD Card using SPI
+ *
+ * @code
+ * #include "mbed.h"
+ * #include "SDBlockDevice.h"
+ *
+ * SDBlockDevice sd(p5, p6, p7, p12); // mosi, miso, sclk, cs
+ * uint8_t block[512] = "Hello World!\n";
+ *
+ * int main() {
+ *     sd.init();
+ *     sd.write(block, 0, 512);
+ *     sd.read(block, 0, 512);
+ *     printf("%s", block);
+ *     sd.deinit();
+ * }
+ */
+class SDBlockDevice : public BlockDevice {
+public:
+    /** Lifetime of an SD card
+     */
+    SDBlockDevice(PinName mosi, PinName miso, PinName sclk, PinName cs);
+    virtual ~SDBlockDevice();
+
+    /** Initialize a block device
+     *
+     *  @return         0 on success or a negative error code on failure
+     */
+    virtual int init();
+
+    /** Deinitialize a block device
+     *
+     *  @return         0 on success or a negative error code on failure
+     */
+    virtual int deinit();
+
+    /** Read blocks from a block device
+     *
+     *  @param buffer   Buffer to write blocks to
+     *  @param addr     Address of block to begin reading from
+     *  @param size     Size to read in bytes, must be a multiple of read block size
+     *  @return         0 on success, negative error code on failure
+     */
+    virtual int read(void *buffer, bd_addr_t addr, bd_size_t size);
+
+    /** Program blocks to a block device
+     *
+     *  The blocks must have been erased prior to being programmed
+     *
+     *  @param buffer   Buffer of data to write to blocks
+     *  @param addr     Address of block to begin writing to
+     *  @param size     Size to write in bytes, must be a multiple of program block size
+     *  @return         0 on success, negative error code on failure
+     */
+    virtual int program(const void *buffer, bd_addr_t addr, bd_size_t size);
+
+    /** Erase blocks on a block device
+     *
+     *  The state of an erased block is undefined until it has been programmed
+     *
+     *  @param addr     Address of block to begin erasing
+     *  @param size     Size to erase in bytes, must be a multiple of erase block size
+     *  @return         0 on success, negative error code on failure
+     */
+    virtual int erase(bd_addr_t addr, bd_size_t size);
+
+    /** Get the size of a readable block
+     *
+     *  @return         Size of a readable block in bytes
+     */
+    virtual bd_size_t get_read_size() const;
+
+    /** Get the size of a programable block
+     *
+     *  @return         Size of a programable block in bytes
+     *  @note Must be a multiple of the read size
+     */
+    virtual bd_size_t get_program_size() const;
+
+    /** Get the size of a eraseable block
+     *
+     *  @return         Size of a eraseable block in bytes
+     *  @note Must be a multiple of the program size
+     */
+    virtual bd_size_t get_erase_size() const;
+
+    /** Get the total size of the underlying device
+     *
+     *  @return         Size of the underlying device in bytes
+     */
+    virtual bd_size_t size() const;
+
+    /** Enable or disable debugging
+     *
+     *  @param          State of debugging
+     */
+    virtual void debug(bool dbg);
+
+private:
+    int _cmd(int cmd, int arg);
+    int _cmdx(int cmd, int arg);
+    int _cmd8();
+    int _cmd58();
+
+    /*  Move the SDCard into the SPI Mode idle state
+     *
+     *  The card is transitioned from SDCard mode to SPI mode by sending the
+     *  CMD0 (GO_IDLE_STATE) command with CS asserted. See the notes in the
+     *  "SPI Startup" section of the comments at the head of the
+     *  implementation file for further details and specification references.
+     *
+     *  @return         -1 if an error occurred e.g. a valid response was not
+     *                  received. Otherwise R1_IDLE_STATE (0x1), the successful
+     *                  response from CMD0.
+     */
+    int _go_idle_state();
+    int _initialise_card();
+    int _initialise_card_v1();
+    int _initialise_card_v2();
+
+    int _read(uint8_t * buffer, uint32_t length);
+    int _write(const uint8_t *buffer, uint32_t length);
+    uint32_t _sd_sectors();
+    uint32_t _sectors;
+
+    uint32_t _init_sck;
+    uint32_t _transfer_sck;
+
+    SPI _spi;
+    DigitalOut _cs;
+    unsigned _block_size;
+    bool _is_initialized;
+    bool _dbg;
+    mutable Mutex _lock;
+};
+
+
+#endif  /* DEVICE_SPI */
+
+#endif  /* MBED_SD_BLOCK_DEVICE_H */
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri Feb 07 07:25:23 2020 +0000
@@ -0,0 +1,55 @@
+/* Copyright (c) 2019 Perlatecnica
+ *
+ * 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.
+ */
+
+/****************************************************
+*            FAST PROTOTYPING WITH NUCLEO           *
+* Example Code 04: SDcard                           *
+* Author: Mauro D'Angelo                            *
+* Organization: Perlatecnica no-profit organization *  
+*****************************************************/
+
+#include "mbed.h"
+
+// It includes the library that manages the File System
+#include "FATFileSystem.h"
+
+// It Includes the library that manage the SD at low level
+#include "SDBlockDevice.h"
+
+// It creates the File System variable
+FATFileSystem fs("fs");
+
+// it creates the reference to SD. The parameters are the pin for SPI bus
+SDBlockDevice sd(D11, D12, D13, D10); //MOSI MISO SCK CS
+
+Serial pc(USBTX, USBRX);
+
+int main() {
+    // It mounts the SD.
+    fs.mount(&sd);
+
+    // It opens the file mbed.txt. 'w' represents the access rights
+    FILE *fd = fopen("/fs/mbed.txt", "w");
+
+    if(fd==NULL) {
+        // Something was wrong
+        pc.printf("Error occurs writing the SD!\r\n");
+    }
+    else {
+        fprintf(fd, "Welcome SD!!\r\n");
+        fclose(fd);
+        pc.printf("It works!\r\n");
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Fri Feb 07 07:25:23 2020 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/teams/EL4121-Embedded-System/code/mbed-os/#b74591d5ab33