takumi funada
/
LCD
testing TextLCD and SD card
Diff: SDFileSystem.cpp
- Revision:
- 0:cc883de36463
diff -r 000000000000 -r cc883de36463 SDFileSystem.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/SDFileSystem.cpp Thu Jul 01 18:01:20 2010 +0000 @@ -0,0 +1,294 @@ +/* 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; +}