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/* mbed Microcontroller Library - SDFileSystem
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* Copyright (c) 2008-2009, sford
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*
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* Introduction
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* ------------
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* SD and MMC cards support a number of interfaces, but common to them all
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* is one based on SPI. This is the one I'm implmenting because it means
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* it is much more portable even though not so performant, and we already
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* have the mbed SPI Interface!
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*
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* The main reference I'm using is Chapter 7, "SPI Mode" of:
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* http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
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*
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* SPI Startup
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* -----------
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* The SD card powers up in SD mode. The SPI interface mode is selected by
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* asserting CS low and sending the reset command (CMD0). The card will
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* respond with a (R1) response.
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*
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* CMD8 is optionally sent to determine the voltage range supported, and
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* indirectly determine whether it is a version 1.x SD/non-SD card or
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* version 2.x. I'll just ignore this for now.
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*
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* ACMD41 is repeatedly issued to initialise the card, until "in idle"
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* (bit 0) of the R1 response goes to '0', indicating it is initialised.
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*
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* You should also indicate whether the host supports High Capicity cards,
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* and check whether the card is high capacity - i'll also ignore this
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*
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* SPI Protocol
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* ------------
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* The SD SPI protocol is based on transactions made up of 8-bit words, with
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* the host starting every bus transaction by asserting the CS signal low. The
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* card always responds to commands, data blocks and errors.
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*
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* The protocol supports a CRC, but by default it is off (except for the
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* first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
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* I'll leave the CRC off I think!
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*
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* Standard capacity cards have variable data block sizes, whereas High
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* Capacity cards fix the size of data block to 512 bytes. I'll therefore
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* just always use the Standard Capacity cards with a block size of 512 bytes.
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* This is set with CMD16.
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*
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* You can read and write single blocks (CMD17, CMD25) or multiple blocks
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* (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
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* the card gets a read command, it responds with a response token, and then
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* a data token or an error.
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*
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* SPI Command Format
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* ------------------
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* Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
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*
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* +---------------+------------+------------+-----------+----------+--------------+
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* | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
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* +---------------+------------+------------+-----------+----------+--------------+
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*
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* As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
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*
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* All Application Specific commands shall be preceded with APP_CMD (CMD55).
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*
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* SPI Response Format
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* -------------------
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* The main response format (R1) is a status byte (normally zero). Key flags:
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* idle - 1 if the card is in an idle state/initialising
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* cmd - 1 if an illegal command code was detected
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*
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* +-------------------------------------------------+
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* R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
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* +-------------------------------------------------+
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*
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* R1b is the same, except it is followed by a busy signal (zeros) until
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* the first non-zero byte when it is ready again.
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*
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* Data Response Token
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* -------------------
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* Every data block written to the card is acknowledged by a byte
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* response token
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*
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* +----------------------+
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* | xxx | 0 | status | 1 |
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* +----------------------+
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* 010 - OK!
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* 101 - CRC Error
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* 110 - Write Error
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*
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* Single Block Read and Write
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* ---------------------------
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*
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* Block transfers have a byte header, followed by the data, followed
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* by a 16-bit CRC. In our case, the data will always be 512 bytes.
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*
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* +------+---------+---------+- - - -+---------+-----------+----------+
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* | 0xFE | data[0] | data[1] | | data[n] | crc[15:8] | crc[7:0] |
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95
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* +------+---------+---------+- - - -+---------+-----------+----------+
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*/
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#include "SDFileSystem.h"
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#define SD_COMMAND_TIMEOUT 5000
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SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
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FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
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_cs = 1;
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}
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int SDFileSystem::disk_initialize() {
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_spi.frequency(100000); // Set to 100kHz for initialisation
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// Initialise the card by clocking it with cs = 1
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_cs = 1;
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for(int i=0; i<16; i++) {
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_spi.write(0xFF);
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}
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// send CMD0, should return with all zeros except IDLE STATE set (bit 0)
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if(_cmd(0, 0) != 0x01) {
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fprintf(stderr, "Not in idle state\n");
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return 1;
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}
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122
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// ACMD41 to give host capacity support (repeat until not busy)
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// ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
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for(int i=0;; i++) {
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_cmd(55, 0);
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int response = _cmd(41, 0);
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if(response == 0) {
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break;
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} else if(i > SD_COMMAND_TIMEOUT) {
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fprintf(stderr, "Timeout waiting for card\n");
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return 1;
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}
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}
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_sectors = _sd_sectors();
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// Set block length to 512 (CMD16)
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if(_cmd(16, 512) != 0) {
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fprintf(stderr, "Set block timeout\n");
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return 1;
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}
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_spi.frequency(1000000); // Set to 1MHz for data transfer
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return 0;
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}
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147
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int SDFileSystem::disk_write(const char *buffer, int block_number) {
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149
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// set write address for single block (CMD24)
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150
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if(_cmd(24, block_number * 512) != 0) {
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151
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return 1;
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}
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153
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154
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// send the data block
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155
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_write(buffer, 512);
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156
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return 0;
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157
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}
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1:2dec995d53f8
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158
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1:2dec995d53f8
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159
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int SDFileSystem::disk_read(char *buffer, int block_number) {
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1:2dec995d53f8
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160
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// set read address for single block (CMD17)
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161
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if(_cmd(17, block_number * 512) != 0) {
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1:2dec995d53f8
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162
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return 1;
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1:2dec995d53f8
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163
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}
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1:2dec995d53f8
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164
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165
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// receive the data
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166
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_read(buffer, 512);
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1:2dec995d53f8
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167
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return 0;
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1:2dec995d53f8
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168
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}
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1:2dec995d53f8
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169
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1:2dec995d53f8
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170
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int SDFileSystem::disk_status() { return 0; }
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171
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int SDFileSystem::disk_sync() { return 0; }
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172
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int SDFileSystem::disk_sectors() { return _sectors; }
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173
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// PRIVATE FUNCTIONS
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175
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int SDFileSystem::_cmd(int cmd, int arg) {
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_cs = 0;
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1:2dec995d53f8
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178
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179
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// send a command
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1:2dec995d53f8
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180
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_spi.write(0x40 | cmd);
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1:2dec995d53f8
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181
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_spi.write(arg >> 24);
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1:2dec995d53f8
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182
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_spi.write(arg >> 16);
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1:2dec995d53f8
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183
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_spi.write(arg >> 8);
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1:2dec995d53f8
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184
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_spi.write(arg >> 0);
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1:2dec995d53f8
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185
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_spi.write(0x95);
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simon |
1:2dec995d53f8
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186
|
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simon |
1:2dec995d53f8
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187
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// wait for the repsonse (response[7] == 0)
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1:2dec995d53f8
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188
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for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
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1:2dec995d53f8
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189
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int response = _spi.write(0xFF);
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1:2dec995d53f8
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190
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if(!(response & 0x80)) {
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1:2dec995d53f8
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191
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_cs = 1;
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1:2dec995d53f8
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192
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_spi.write(0xFF);
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1:2dec995d53f8
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193
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return response;
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1:2dec995d53f8
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194
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}
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1:2dec995d53f8
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195
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}
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1:2dec995d53f8
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196
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_cs = 1;
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1:2dec995d53f8
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197
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_spi.write(0xFF);
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1:2dec995d53f8
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198
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return -1; // timeout
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1:2dec995d53f8
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199
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}
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simon |
1:2dec995d53f8
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200
|
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simon |
1:2dec995d53f8
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201
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int SDFileSystem::_read(char *buffer, int length) {
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1:2dec995d53f8
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202
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_cs = 0;
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simon |
1:2dec995d53f8
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203
|
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simon |
1:2dec995d53f8
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204
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// read until start byte (0xFF)
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1:2dec995d53f8
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205
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while(_spi.write(0xFF) != 0xFE);
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1:2dec995d53f8
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206
|
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simon |
1:2dec995d53f8
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207
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// read data
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simon |
1:2dec995d53f8
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208
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for(int i=0; i<length; i++) {
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1:2dec995d53f8
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209
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buffer[i] = _spi.write(0xFF);
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1:2dec995d53f8
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210
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}
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simon |
1:2dec995d53f8
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211
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_spi.write(0xFF); // checksum
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1:2dec995d53f8
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212
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_spi.write(0xFF);
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1:2dec995d53f8
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213
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1:2dec995d53f8
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214
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_cs = 1;
|
simon |
1:2dec995d53f8
|
215
|
_spi.write(0xFF);
|
simon |
1:2dec995d53f8
|
216
|
return 0;
|
simon |
1:2dec995d53f8
|
217
|
}
|
simon |
1:2dec995d53f8
|
218
|
|
simon |
1:2dec995d53f8
|
219
|
int SDFileSystem::_write(const char *buffer, int length) {
|
simon |
1:2dec995d53f8
|
220
|
_cs = 0;
|
simon |
1:2dec995d53f8
|
221
|
|
simon |
1:2dec995d53f8
|
222
|
// indicate start of block
|
simon |
1:2dec995d53f8
|
223
|
_spi.write(0xFE);
|
simon |
1:2dec995d53f8
|
224
|
|
simon |
1:2dec995d53f8
|
225
|
// write the data
|
simon |
1:2dec995d53f8
|
226
|
for(int i=0; i<length; i++) {
|
simon |
1:2dec995d53f8
|
227
|
_spi.write(buffer[i]);
|
simon |
1:2dec995d53f8
|
228
|
}
|
simon |
1:2dec995d53f8
|
229
|
|
simon |
1:2dec995d53f8
|
230
|
// write the checksum
|
simon |
1:2dec995d53f8
|
231
|
_spi.write(0xFF);
|
simon |
1:2dec995d53f8
|
232
|
_spi.write(0xFF);
|
simon |
1:2dec995d53f8
|
233
|
|
simon |
1:2dec995d53f8
|
234
|
// check the repsonse token
|
simon |
1:2dec995d53f8
|
235
|
if((_spi.write(0xFF) & 0x1F) != 0x05) {
|
simon |
1:2dec995d53f8
|
236
|
_cs = 1;
|
simon |
1:2dec995d53f8
|
237
|
_spi.write(0xFF);
|
simon |
1:2dec995d53f8
|
238
|
return 1;
|
simon |
1:2dec995d53f8
|
239
|
}
|
simon |
1:2dec995d53f8
|
240
|
|
simon |
1:2dec995d53f8
|
241
|
// wait for write to finish
|
simon |
1:2dec995d53f8
|
242
|
while(_spi.write(0xFF) == 0);
|
simon |
1:2dec995d53f8
|
243
|
|
simon |
1:2dec995d53f8
|
244
|
_cs = 1;
|
simon |
1:2dec995d53f8
|
245
|
_spi.write(0xFF);
|
simon |
1:2dec995d53f8
|
246
|
return 0;
|
simon |
1:2dec995d53f8
|
247
|
}
|
simon |
1:2dec995d53f8
|
248
|
|
simon |
1:2dec995d53f8
|
249
|
static int ext_bits(char *data, int msb, int lsb) {
|
simon |
1:2dec995d53f8
|
250
|
int bits = 0;
|
simon |
1:2dec995d53f8
|
251
|
int size = 1 + msb - lsb;
|
simon |
1:2dec995d53f8
|
252
|
for(int i=0; i<size; i++) {
|
simon |
1:2dec995d53f8
|
253
|
int position = lsb + i;
|
simon |
1:2dec995d53f8
|
254
|
int byte = 15 - (position >> 3);
|
simon |
1:2dec995d53f8
|
255
|
int bit = position & 0x7;
|
simon |
1:2dec995d53f8
|
256
|
int value = (data[byte] >> bit) & 1;
|
simon |
1:2dec995d53f8
|
257
|
bits |= value << i;
|
simon |
1:2dec995d53f8
|
258
|
}
|
simon |
1:2dec995d53f8
|
259
|
return bits;
|
simon |
1:2dec995d53f8
|
260
|
}
|
simon |
1:2dec995d53f8
|
261
|
|
simon |
1:2dec995d53f8
|
262
|
int SDFileSystem::_sd_sectors() {
|
simon |
1:2dec995d53f8
|
263
|
|
simon |
1:2dec995d53f8
|
264
|
// CMD9, Response R2 (R1 byte + 16-byte block read)
|
simon |
1:2dec995d53f8
|
265
|
if(_cmd(9, 0) != 0) {
|
simon |
1:2dec995d53f8
|
266
|
fprintf(stderr, "Didn't get a response from the disk\n");
|
simon |
1:2dec995d53f8
|
267
|
return 0;
|
simon |
1:2dec995d53f8
|
268
|
}
|
simon |
1:2dec995d53f8
|
269
|
|
simon |
1:2dec995d53f8
|
270
|
char csd[16];
|
simon |
1:2dec995d53f8
|
271
|
if(_read(csd, 16) != 0) {
|
simon |
1:2dec995d53f8
|
272
|
fprintf(stderr, "Couldn't read csd response from disk\n");
|
simon |
1:2dec995d53f8
|
273
|
return 0;
|
simon |
1:2dec995d53f8
|
274
|
}
|
simon |
1:2dec995d53f8
|
275
|
|
simon |
1:2dec995d53f8
|
276
|
// csd_structure : csd[127:126]
|
simon |
1:2dec995d53f8
|
277
|
// c_size : csd[73:62]
|
simon |
1:2dec995d53f8
|
278
|
// c_size_mult : csd[49:47]
|
simon |
1:2dec995d53f8
|
279
|
// read_bl_len : csd[83:80]
|
simon |
1:2dec995d53f8
|
280
|
|
simon |
1:2dec995d53f8
|
281
|
int csd_structure = ext_bits(csd, 127, 126);
|
simon |
1:2dec995d53f8
|
282
|
int c_size = ext_bits(csd, 73, 62);
|
simon |
1:2dec995d53f8
|
283
|
int c_size_mult = ext_bits(csd, 49, 47);
|
simon |
1:2dec995d53f8
|
284
|
int read_bl_len = ext_bits(csd, 83, 80);
|
simon |
1:2dec995d53f8
|
285
|
|
simon |
1:2dec995d53f8
|
286
|
if(csd_structure != 0) {
|
simon |
1:2dec995d53f8
|
287
|
fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
|
simon |
1:2dec995d53f8
|
288
|
return 0;
|
simon |
1:2dec995d53f8
|
289
|
}
|
simon |
1:2dec995d53f8
|
290
|
|
simon |
1:2dec995d53f8
|
291
|
int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
|
simon |
1:2dec995d53f8
|
292
|
int block_size = 1 << read_bl_len;
|
simon |
1:2dec995d53f8
|
293
|
|
simon |
1:2dec995d53f8
|
294
|
if(block_size != 512) {
|
simon |
1:2dec995d53f8
|
295
|
fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
|
simon |
1:2dec995d53f8
|
296
|
return 0;
|
simon |
1:2dec995d53f8
|
297
|
}
|
simon |
1:2dec995d53f8
|
298
|
|
simon |
1:2dec995d53f8
|
299
|
return blocks;
|
simon |
1:2dec995d53f8
|
300
|
}
|