Brian Daniels
Fork of USBMSD_SD
Fork of
USBMSD_SD
by 
Samuel Mokrani
Diff: USBMSD_SD.cpp
- Revision:
- 0:de50a209c5a9
- Child:
- 1:923991b026e7
diff -r 000000000000 -r de50a209c5a9 USBMSD_SD.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/USBMSD_SD.cpp Sun Dec 11 15:17:54 2011 +0000
@@ -0,0 +1,463 @@
+/* mbed USBMSD_SD Library, for providing file access to SD cards
+ * Copyright (c) 2008-2010, sford
+ *
+ * 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 SPI interface mode is selected by
+ * asserting CS low and sending the reset command (CMD0). The card will
+ * respond with a (R1) response.
+ *
+ * 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] |
+ * +------+---------+---------+- - - -+---------+-----------+----------+
+ */
+
+#include "USBMSD_SD.h"
+
+#define SD_COMMAND_TIMEOUT 5000
+
+USBMSD_SD::USBMSD_SD(PinName mosi, PinName miso, PinName sclk, PinName cs) :
+ _spi(mosi, miso, sclk), _cs(cs) {
+ _cs = 1;
+ connect();
+}
+
+#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 USBMSD_SD::initialise_card() {
+ // Set to 100kHz for initialisation, and clock card with cs = 1
+ _spi.frequency(100000);
+ _cs = 1;
+ for(int i=0; i<16; i++) {
+ _spi.write(0xFF);
+ }
+
+ // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
+ if(_cmd(0, 0) != R1_IDLE_STATE) {
+ fprintf(stderr, "No disk, or could not put SD card in to SPI idle state\n");
+ return SDCARD_FAIL;
+ }
+
+ // send CMD8 to determine whther 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 {
+ fprintf(stderr, "Not in idle state after sending CMD8 (not an SD card?)\n");
+ return SDCARD_FAIL;
+ }
+}
+
+int USBMSD_SD::initialise_card_v1() {
+ for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
+ _cmd(55, 0);
+ if(_cmd(41, 0) == 0) {
+ return SDCARD_V1;
+ }
+ }
+
+ fprintf(stderr, "Timeout waiting for v1.x card\n");
+ return SDCARD_FAIL;
+}
+
+int USBMSD_SD::initialise_card_v2() {
+
+ for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
+ _cmd(55, 0);
+ if(_cmd(41, 0) == 0) {
+ _cmd58();
+ return SDCARD_V2;
+ }
+ }
+
+ fprintf(stderr, "Timeout waiting for v2.x card\n");
+ return SDCARD_FAIL;
+}
+
+int USBMSD_SD::disk_initialize() {
+
+ int i = initialise_card();
+// printf("init card = %d\n", i);
+// printf("OK\n");
+
+ _sectors = _sd_sectors();
+
+ // Set block length to 512 (CMD16)
+ if(_cmd(16, 512) != 0) {
+ fprintf(stderr, "Set 512-byte block timed out\n");
+ return 1;
+ }
+
+ _spi.frequency(5000000); // Set to 5MHz for data transfer
+ return 0;
+}
+
+int USBMSD_SD::disk_write(const char *buffer, int block_number) {
+ // set write address for single block (CMD24)
+ if(_cmd(24, block_number * 512) != 0) {
+ return 1;
+ }
+
+ // send the data block
+ _write(buffer, 512);
+ return 0;
+}
+
+int USBMSD_SD::disk_read(char *buffer, int block_number) {
+ // set read address for single block (CMD17)
+ if(_cmd(17, block_number * 512) != 0) {
+ return 1;
+ }
+
+ // receive the data
+ _read(buffer, 512);
+ return 0;
+}
+
+int USBMSD_SD::disk_status() { return 0; }
+int USBMSD_SD::disk_sync() { return 0; }
+int USBMSD_SD::disk_sectors() { return _sectors; }
+
+// PRIVATE FUNCTIONS
+
+int USBMSD_SD::_cmd(int cmd, int arg) {
+ _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 repsonse (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);
+ return response;
+ }
+ }
+ _cs = 1;
+ _spi.write(0xFF);
+ return -1; // timeout
+}
+int USBMSD_SD::_cmdx(int cmd, int arg) {
+ _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 repsonse (response[7] == 0)
+ for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
+ int response = _spi.write(0xFF);
+ if(!(response & 0x80)) {
+ return response;
+ }
+ }
+ _cs = 1;
+ _spi.write(0xFF);
+ return -1; // timeout
+}
+
+
+int USBMSD_SD::_cmd58() {
+ _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 repsonse (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;
+// printf("OCR = 0x%08X\n", ocr);
+ _cs = 1;
+ _spi.write(0xFF);
+ return response;
+ }
+ }
+ _cs = 1;
+ _spi.write(0xFF);
+ return -1; // timeout
+}
+
+int USBMSD_SD::_cmd8() {
+ _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 repsonse (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);
+ return response[0];
+ }
+ }
+ _cs = 1;
+ _spi.write(0xFF);
+ return -1; // timeout
+}
+
+int USBMSD_SD::_read(char *buffer, int length) {
+ _cs = 0;
+
+ // read until start byte (0xFF)
+ while(_spi.write(0xFF) != 0xFE);
+
+ // read data
+ for(int i=0; i<length; i++) {
+ buffer[i] = _spi.write(0xFF);
+ }
+ _spi.write(0xFF); // checksum
+ _spi.write(0xFF);
+
+ _cs = 1;
+ _spi.write(0xFF);
+ return 0;
+}
+
+int USBMSD_SD::_write(const char *buffer, int length) {
+ _cs = 0;
+
+ // indicate start of block
+ _spi.write(0xFE);
+
+ // write the data
+ for(int i=0; i<length; i++) {
+ _spi.write(buffer[i]);
+ }
+
+ // write the checksum
+ _spi.write(0xFF);
+ _spi.write(0xFF);
+
+ // check the repsonse token
+ if((_spi.write(0xFF) & 0x1F) != 0x05) {
+ _cs = 1;
+ _spi.write(0xFF);
+ return 1;
+ }
+
+ // wait for write to finish
+ while(_spi.write(0xFF) == 0);
+
+ _cs = 1;
+ _spi.write(0xFF);
+ return 0;
+}
+
+static int ext_bits(char *data, int msb, int lsb) {
+ int bits = 0;
+ int size = 1 + msb - lsb;
+ for(int i=0; i<size; i++) {
+ int position = lsb + i;
+ int byte = 15 - (position >> 3);
+ int bit = position & 0x7;
+ int value = (data[byte] >> bit) & 1;
+ bits |= value << i;
+ }
+ return bits;
+}
+
+int USBMSD_SD::_sd_sectors() {
+
+ // CMD9, Response R2 (R1 byte + 16-byte block read)
+ if(_cmdx(9, 0) != 0) {
+ fprintf(stderr, "Didn't get a response from the disk\n");
+ return 0;
+ }
+
+ char csd[16];
+ if(_read(csd, 16) != 0) {
+ fprintf(stderr, "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);
+ int c_size = ext_bits(csd, 73, 62);
+ int c_size_mult = ext_bits(csd, 49, 47);
+ int read_bl_len = ext_bits(csd, 83, 80);
+
+// printf("CSD_STRUCT = %d\n", csd_structure);
+
+ if(csd_structure != 0) {
+ fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures\n");
+ return 0;
+ }
+
+ // memory capacity = BLOCKNR * BLOCK_LEN
+ // where
+ // BLOCKNR = (C_SIZE+1) * MULT
+ // MULT = 2^(C_SIZE_MULT+2) (C_SIZE_MULT < 8)
+ // BLOCK_LEN = 2^READ_BL_LEN, (READ_BL_LEN < 12)
+
+ int block_len = 1 << read_bl_len;
+ int mult = 1 << (c_size_mult + 2);
+ int blocknr = (c_size + 1) * mult;
+ capacity = blocknr * block_len;
+
+ int blocks = capacity / 512;
+
+ return blocks;
+}
+
+
+int USBMSD_SD::disk_size() {
+ return capacity;
+}