Diff: SDFileSystem.cpp
- Revision:
- 1:2dec995d53f8
- Parent:
- 0:666a082cf50f
- Child:
- 2:849162a1207f
--- a/SDFileSystem.cpp Thu Nov 19 14:04:44 2009 +0000
+++ b/SDFileSystem.cpp Mon Dec 14 20:31:54 2009 +0000
@@ -1,294 +1,300 @@
-/* mbed Microcontroller Library - SDFileSystem
- * Copyright (c) 2008-2009, sford
- *
- * 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 "SDFileSystem.h"
-
-#define SD_COMMAND_TIMEOUT 5000
-
-SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
- FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
- _cs = 1;
-}
-
-int SDFileSystem::disk_initialize() {
-
- _spi.frequency(100000); // Set to 100kHz for initialisation
-
- // Initialise the card by clocking it a bit (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) != 0x01) {
- fprintf(stderr, "Not in idle state\n");
- return 1;
- }
-
- // ACMD41 to give host capacity support (repeat until not busy)
- // ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
- for(int i=0;; i++) {
- _cmd(55, 0);
- int response = _cmd(41, 0);
- if(response == 0) {
- break;
- } else if(i > SD_COMMAND_TIMEOUT) {
- fprintf(stderr, "Timeout waiting for card\n");
- return 1;
- }
- }
-
- _sectors = _sd_sectors();
-
- // Set block length to 512 (CMD16)
- if(_cmd(16, 512) != 0) {
- fprintf(stderr, "Set block timeout\n");
- return 1;
- }
-
- _spi.frequency(1000000); // Set to 1MHz for data transfer
- return 0;
-}
-
-int SDFileSystem::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 SDFileSystem::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 SDFileSystem::disk_status() { return 0; }
-int SDFileSystem::disk_sync() { return 0; }
-int SDFileSystem::disk_sectors() { return _sectors; }
-
-// PRIVATE FUNCTIONS
-
-int SDFileSystem::_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;
- return response;
- }
- }
- _cs = 1;
- return -1; // timeout
-}
-
-int SDFileSystem::_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;
- return 0;
-}
-
-int SDFileSystem::_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;
- return 1;
- }
-
- // wait for write to finish
- while(_spi.write(0xFF) == 0);
-
- _cs = 1;
- 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 SDFileSystem::_sd_sectors() {
-
- // CMD9, Response R2 (R1 byte + 16-byte block read)
- if(_cmd(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]
-
- 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);
-
- if(csd_structure != 0) {
- fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
- return 0;
- }
-
- int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
- int block_size = 1 << read_bl_len;
-
- if(block_size != 512) {
- fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
- return 0;
- }
-
- return blocks;
-}
+/* mbed Microcontroller Library - SDFileSystem
+ * Copyright (c) 2008-2009, sford
+ *
+ * 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 "SDFileSystem.h"
+
+#define SD_COMMAND_TIMEOUT 5000
+
+SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
+ FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
+ _cs = 1;
+}
+
+int SDFileSystem::disk_initialize() {
+
+ _spi.frequency(100000); // Set to 100kHz for initialisation
+
+ // Initialise the card by clocking it with cs = 1
+ _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) != 0x01) {
+ fprintf(stderr, "Not in idle state\n");
+ return 1;
+ }
+
+ // ACMD41 to give host capacity support (repeat until not busy)
+ // ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
+ for(int i=0;; i++) {
+ _cmd(55, 0);
+ int response = _cmd(41, 0);
+ if(response == 0) {
+ break;
+ } else if(i > SD_COMMAND_TIMEOUT) {
+ fprintf(stderr, "Timeout waiting for card\n");
+ return 1;
+ }
+ }
+
+ _sectors = _sd_sectors();
+
+ // Set block length to 512 (CMD16)
+ if(_cmd(16, 512) != 0) {
+ fprintf(stderr, "Set block timeout\n");
+ return 1;
+ }
+
+ _spi.frequency(1000000); // Set to 1MHz for data transfer
+ return 0;
+}
+
+int SDFileSystem::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 SDFileSystem::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 SDFileSystem::disk_status() { return 0; }
+int SDFileSystem::disk_sync() { return 0; }
+int SDFileSystem::disk_sectors() { return _sectors; }
+
+// PRIVATE FUNCTIONS
+
+int SDFileSystem::_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 SDFileSystem::_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 SDFileSystem::_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 SDFileSystem::_sd_sectors() {
+
+ // CMD9, Response R2 (R1 byte + 16-byte block read)
+ if(_cmd(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]
+
+ 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);
+
+ if(csd_structure != 0) {
+ fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
+ return 0;
+ }
+
+ int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
+ int block_size = 1 << read_bl_len;
+
+ if(block_size != 512) {
+ fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
+ return 0;
+ }
+
+ return blocks;
+}
Simon Ford