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SDFileSystem.cpp@0:b545e012d041, 2009-11-25 (annotated)

Committer:: DaveStyles
Date:: Wed Nov 25 22:37:12 2009 +0000
Revision:: 0:b545e012d041

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User	Revision	Line number	New contents of line
DaveStyles	0:b545e012d041	1	/* mbed Microcontroller Library - SDFileSystem
DaveStyles	0:b545e012d041	2	* Copyright (c) 2008-2009, sford
DaveStyles	0:b545e012d041	3	*
DaveStyles	0:b545e012d041	4	* Introduction
DaveStyles	0:b545e012d041	5	* ------------
DaveStyles	0:b545e012d041	6	* SD and MMC cards support a number of interfaces, but common to them all
DaveStyles	0:b545e012d041	7	* is one based on SPI. This is the one I'm implmenting because it means
DaveStyles	0:b545e012d041	8	* it is much more portable even though not so performant, and we already
DaveStyles	0:b545e012d041	9	* have the mbed SPI Interface!
DaveStyles	0:b545e012d041	10	*
DaveStyles	0:b545e012d041	11	* The main reference I'm using is Chapter 7, "SPI Mode" of:
DaveStyles	0:b545e012d041	12	* http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
DaveStyles	0:b545e012d041	13	*
DaveStyles	0:b545e012d041	14	* SPI Startup
DaveStyles	0:b545e012d041	15	* -----------
DaveStyles	0:b545e012d041	16	* The SD card powers up in SD mode. The SPI interface mode is selected by
DaveStyles	0:b545e012d041	17	* asserting CS low and sending the reset command (CMD0). The card will
DaveStyles	0:b545e012d041	18	* respond with a (R1) response.
DaveStyles	0:b545e012d041	19	*
DaveStyles	0:b545e012d041	20	* CMD8 is optionally sent to determine the voltage range supported, and
DaveStyles	0:b545e012d041	21	* indirectly determine whether it is a version 1.x SD/non-SD card or
DaveStyles	0:b545e012d041	22	* version 2.x. I'll just ignore this for now.
DaveStyles	0:b545e012d041	23	*
DaveStyles	0:b545e012d041	24	* ACMD41 is repeatedly issued to initialise the card, until "in idle"
DaveStyles	0:b545e012d041	25	* (bit 0) of the R1 response goes to '0', indicating it is initialised.
DaveStyles	0:b545e012d041	26	*
DaveStyles	0:b545e012d041	27	* You should also indicate whether the host supports High Capicity cards,
DaveStyles	0:b545e012d041	28	* and check whether the card is high capacity - i'll also ignore this
DaveStyles	0:b545e012d041	29	*
DaveStyles	0:b545e012d041	30	* SPI Protocol
DaveStyles	0:b545e012d041	31	* ------------
DaveStyles	0:b545e012d041	32	* The SD SPI protocol is based on transactions made up of 8-bit words, with
DaveStyles	0:b545e012d041	33	* the host starting every bus transaction by asserting the CS signal low. The
DaveStyles	0:b545e012d041	34	* card always responds to commands, data blocks and errors.
DaveStyles	0:b545e012d041	35	*
DaveStyles	0:b545e012d041	36	* The protocol supports a CRC, but by default it is off (except for the
DaveStyles	0:b545e012d041	37	* first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
DaveStyles	0:b545e012d041	38	* I'll leave the CRC off I think!
DaveStyles	0:b545e012d041	39	*
DaveStyles	0:b545e012d041	40	* Standard capacity cards have variable data block sizes, whereas High
DaveStyles	0:b545e012d041	41	* Capacity cards fix the size of data block to 512 bytes. I'll therefore
DaveStyles	0:b545e012d041	42	* just always use the Standard Capacity cards with a block size of 512 bytes.
DaveStyles	0:b545e012d041	43	* This is set with CMD16.
DaveStyles	0:b545e012d041	44	*
DaveStyles	0:b545e012d041	45	* You can read and write single blocks (CMD17, CMD25) or multiple blocks
DaveStyles	0:b545e012d041	46	* (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
DaveStyles	0:b545e012d041	47	* the card gets a read command, it responds with a response token, and then
DaveStyles	0:b545e012d041	48	* a data token or an error.
DaveStyles	0:b545e012d041	49	*
DaveStyles	0:b545e012d041	50	* SPI Command Format
DaveStyles	0:b545e012d041	51	* ------------------
DaveStyles	0:b545e012d041	52	* Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
DaveStyles	0:b545e012d041	53	*
DaveStyles	0:b545e012d041	54	* +---------------+------------+------------+-----------+----------+--------------+
DaveStyles	0:b545e012d041	55	* \| 01 \| cmd[5:0] \| arg[31:24] \| arg[23:16] \| arg[15:8] \| arg[7:0] \| crc[6:0] \| 1 \|
DaveStyles	0:b545e012d041	56	* +---------------+------------+------------+-----------+----------+--------------+
DaveStyles	0:b545e012d041	57	*
DaveStyles	0:b545e012d041	58	* As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
DaveStyles	0:b545e012d041	59	*
DaveStyles	0:b545e012d041	60	* All Application Specific commands shall be preceded with APP_CMD (CMD55).
DaveStyles	0:b545e012d041	61	*
DaveStyles	0:b545e012d041	62	* SPI Response Format
DaveStyles	0:b545e012d041	63	* -------------------
DaveStyles	0:b545e012d041	64	* The main response format (R1) is a status byte (normally zero). Key flags:
DaveStyles	0:b545e012d041	65	* idle - 1 if the card is in an idle state/initialising
DaveStyles	0:b545e012d041	66	* cmd - 1 if an illegal command code was detected
DaveStyles	0:b545e012d041	67	*
DaveStyles	0:b545e012d041	68	* +-------------------------------------------------+
DaveStyles	0:b545e012d041	69	* R1 \| 0 \| arg \| addr \| seq \| crc \| cmd \| erase \| idle \|
DaveStyles	0:b545e012d041	70	* +-------------------------------------------------+
DaveStyles	0:b545e012d041	71	*
DaveStyles	0:b545e012d041	72	* R1b is the same, except it is followed by a busy signal (zeros) until
DaveStyles	0:b545e012d041	73	* the first non-zero byte when it is ready again.
DaveStyles	0:b545e012d041	74	*
DaveStyles	0:b545e012d041	75	* Data Response Token
DaveStyles	0:b545e012d041	76	* -------------------
DaveStyles	0:b545e012d041	77	* Every data block written to the card is acknowledged by a byte
DaveStyles	0:b545e012d041	78	* response token
DaveStyles	0:b545e012d041	79	*
DaveStyles	0:b545e012d041	80	* +----------------------+
DaveStyles	0:b545e012d041	81	* \| xxx \| 0 \| status \| 1 \|
DaveStyles	0:b545e012d041	82	* +----------------------+
DaveStyles	0:b545e012d041	83	* 010 - OK!
DaveStyles	0:b545e012d041	84	* 101 - CRC Error
DaveStyles	0:b545e012d041	85	* 110 - Write Error
DaveStyles	0:b545e012d041	86	*
DaveStyles	0:b545e012d041	87	* Single Block Read and Write
DaveStyles	0:b545e012d041	88	* ---------------------------
DaveStyles	0:b545e012d041	89	*
DaveStyles	0:b545e012d041	90	* Block transfers have a byte header, followed by the data, followed
DaveStyles	0:b545e012d041	91	* by a 16-bit CRC. In our case, the data will always be 512 bytes.
DaveStyles	0:b545e012d041	92	*
DaveStyles	0:b545e012d041	93	* +------+---------+---------+- - - -+---------+-----------+----------+
DaveStyles	0:b545e012d041	94	* \| 0xFE \| data[0] \| data[1] \| \| data[n] \| crc[15:8] \| crc[7:0] \|
DaveStyles	0:b545e012d041	95	* +------+---------+---------+- - - -+---------+-----------+----------+
DaveStyles	0:b545e012d041	96	*/
DaveStyles	0:b545e012d041	97
DaveStyles	0:b545e012d041	98	#include "SDFileSystem.h"
DaveStyles	0:b545e012d041	99
DaveStyles	0:b545e012d041	100	#define SD_COMMAND_TIMEOUT 5000
DaveStyles	0:b545e012d041	101
DaveStyles	0:b545e012d041	102	SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
DaveStyles	0:b545e012d041	103	FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
DaveStyles	0:b545e012d041	104	_cs = 1;
DaveStyles	0:b545e012d041	105	}
DaveStyles	0:b545e012d041	106
DaveStyles	0:b545e012d041	107	int SDFileSystem::disk_initialize() {
DaveStyles	0:b545e012d041	108
DaveStyles	0:b545e012d041	109	fprintf(stderr,"Initialising\n");
DaveStyles	0:b545e012d041	110
DaveStyles	0:b545e012d041	111
DaveStyles	0:b545e012d041	112	_spi.frequency(1000); // Set to 100kHz for initialisation
DaveStyles	0:b545e012d041	113
DaveStyles	0:b545e012d041	114	// Initialise the card by clocking it a bit (cs = 1)
DaveStyles	0:b545e012d041	115	for(int i=0; i<16; i++) {
DaveStyles	0:b545e012d041	116	_spi.write(0xFF);
DaveStyles	0:b545e012d041	117	}
DaveStyles	0:b545e012d041	118
DaveStyles	0:b545e012d041	119	// send CMD0, should return with all zeros except IDLE STATE set (bit 0)
DaveStyles	0:b545e012d041	120	if(_cmd(0, 0) != 0x01) {
DaveStyles	0:b545e012d041	121	fprintf(stderr, "Not in idle state\n");
DaveStyles	0:b545e012d041	122	return 1;
DaveStyles	0:b545e012d041	123	}
DaveStyles	0:b545e012d041	124
DaveStyles	0:b545e012d041	125	// ACMD41 to give host capacity support (repeat until not busy)
DaveStyles	0:b545e012d041	126	// ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
DaveStyles	0:b545e012d041	127	for(int i=0;; i++) {
DaveStyles	0:b545e012d041	128	_cmd(55, 0);
DaveStyles	0:b545e012d041	129	int response = _cmd(41, 0);
DaveStyles	0:b545e012d041	130	if(response == 0) {
DaveStyles	0:b545e012d041	131	break;
DaveStyles	0:b545e012d041	132	} else if(i > SD_COMMAND_TIMEOUT) {
DaveStyles	0:b545e012d041	133	fprintf(stderr, "Timeout waiting for card\n");
DaveStyles	0:b545e012d041	134	return 1;
DaveStyles	0:b545e012d041	135	}
DaveStyles	0:b545e012d041	136	}
DaveStyles	0:b545e012d041	137
DaveStyles	0:b545e012d041	138	_sectors = _sd_sectors();
DaveStyles	0:b545e012d041	139
DaveStyles	0:b545e012d041	140	// Set block length to 512 (CMD16)
DaveStyles	0:b545e012d041	141	if(_cmd(16, 512) != 0) {
DaveStyles	0:b545e012d041	142	fprintf(stderr, "Set block timeout\n");
DaveStyles	0:b545e012d041	143	return 1;
DaveStyles	0:b545e012d041	144	}
DaveStyles	0:b545e012d041	145
DaveStyles	0:b545e012d041	146	_spi.frequency(1000000); // Set to 1MHz for data transfer
DaveStyles	0:b545e012d041	147	return 0;
DaveStyles	0:b545e012d041	148	}
DaveStyles	0:b545e012d041	149
DaveStyles	0:b545e012d041	150	int SDFileSystem::disk_write(const char *buffer, int block_number) {
DaveStyles	0:b545e012d041	151	// set write address for single block (CMD24)
DaveStyles	0:b545e012d041	152	if(_cmd(24, block_number * 512) != 0) {
DaveStyles	0:b545e012d041	153	return 1;
DaveStyles	0:b545e012d041	154	}
DaveStyles	0:b545e012d041	155
DaveStyles	0:b545e012d041	156	// send the data block
DaveStyles	0:b545e012d041	157	_write(buffer, 512);
DaveStyles	0:b545e012d041	158	return 0;
DaveStyles	0:b545e012d041	159	}
DaveStyles	0:b545e012d041	160
DaveStyles	0:b545e012d041	161	int SDFileSystem::disk_read(char *buffer, int block_number) {
DaveStyles	0:b545e012d041	162	// set read address for single block (CMD17)
DaveStyles	0:b545e012d041	163	if(_cmd(17, block_number * 512) != 0) {
DaveStyles	0:b545e012d041	164	return 1;
DaveStyles	0:b545e012d041	165	}
DaveStyles	0:b545e012d041	166
DaveStyles	0:b545e012d041	167	// receive the data
DaveStyles	0:b545e012d041	168	_read(buffer, 512);
DaveStyles	0:b545e012d041	169	return 0;
DaveStyles	0:b545e012d041	170	}
DaveStyles	0:b545e012d041	171
DaveStyles	0:b545e012d041	172	int SDFileSystem::disk_status() { return 0; }
DaveStyles	0:b545e012d041	173	int SDFileSystem::disk_sync() { return 0; }
DaveStyles	0:b545e012d041	174	int SDFileSystem::disk_sectors() { return _sectors; }
DaveStyles	0:b545e012d041	175
DaveStyles	0:b545e012d041	176	// PRIVATE FUNCTIONS
DaveStyles	0:b545e012d041	177
DaveStyles	0:b545e012d041	178	int SDFileSystem::_cmd(int cmd, int arg) {
DaveStyles	0:b545e012d041	179	_cs = 0;
DaveStyles	0:b545e012d041	180
DaveStyles	0:b545e012d041	181	// send a command
DaveStyles	0:b545e012d041	182	_spi.write(0x40 \| cmd);
DaveStyles	0:b545e012d041	183	_spi.write(arg >> 24);
DaveStyles	0:b545e012d041	184	_spi.write(arg >> 16);
DaveStyles	0:b545e012d041	185	_spi.write(arg >> 8);
DaveStyles	0:b545e012d041	186	_spi.write(arg >> 0);
DaveStyles	0:b545e012d041	187	_spi.write(0x95);
DaveStyles	0:b545e012d041	188
DaveStyles	0:b545e012d041	189	// wait for the repsonse (response[7] == 0)
DaveStyles	0:b545e012d041	190	for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
DaveStyles	0:b545e012d041	191	int response = _spi.write(0xFF);
DaveStyles	0:b545e012d041	192	if(!(response & 0x80)) {
DaveStyles	0:b545e012d041	193	_cs = 1;
DaveStyles	0:b545e012d041	194	return response;
DaveStyles	0:b545e012d041	195	}
DaveStyles	0:b545e012d041	196	}
DaveStyles	0:b545e012d041	197	_cs = 1;
DaveStyles	0:b545e012d041	198	return -1; // timeout
DaveStyles	0:b545e012d041	199	}
DaveStyles	0:b545e012d041	200
DaveStyles	0:b545e012d041	201	int SDFileSystem::_read(char *buffer, int length) {
DaveStyles	0:b545e012d041	202	_cs = 0;
DaveStyles	0:b545e012d041	203
DaveStyles	0:b545e012d041	204	// read until start byte (0xFF)
DaveStyles	0:b545e012d041	205	while(_spi.write(0xFF) != 0xFE);
DaveStyles	0:b545e012d041	206
DaveStyles	0:b545e012d041	207	// read data
DaveStyles	0:b545e012d041	208	for(int i=0; i<length; i++) {
DaveStyles	0:b545e012d041	209	buffer[i] = _spi.write(0xFF);
DaveStyles	0:b545e012d041	210	}
DaveStyles	0:b545e012d041	211	_spi.write(0xFF); // checksum
DaveStyles	0:b545e012d041	212	_spi.write(0xFF);
DaveStyles	0:b545e012d041	213
DaveStyles	0:b545e012d041	214	_cs = 1;
DaveStyles	0:b545e012d041	215	return 0;
DaveStyles	0:b545e012d041	216	}
DaveStyles	0:b545e012d041	217
DaveStyles	0:b545e012d041	218	int SDFileSystem::_write(const char *buffer, int length) {
DaveStyles	0:b545e012d041	219	_cs = 0;
DaveStyles	0:b545e012d041	220
DaveStyles	0:b545e012d041	221	// indicate start of block
DaveStyles	0:b545e012d041	222	_spi.write(0xFE);
DaveStyles	0:b545e012d041	223
DaveStyles	0:b545e012d041	224	// write the data
DaveStyles	0:b545e012d041	225	for(int i=0; i<length; i++) {
DaveStyles	0:b545e012d041	226	_spi.write(buffer[i]);
DaveStyles	0:b545e012d041	227	}
DaveStyles	0:b545e012d041	228
DaveStyles	0:b545e012d041	229	// write the checksum
DaveStyles	0:b545e012d041	230	_spi.write(0xFF);
DaveStyles	0:b545e012d041	231	_spi.write(0xFF);
DaveStyles	0:b545e012d041	232
DaveStyles	0:b545e012d041	233	// check the repsonse token
DaveStyles	0:b545e012d041	234	if((_spi.write(0xFF) & 0x1F) != 0x05) {
DaveStyles	0:b545e012d041	235	_cs = 1;
DaveStyles	0:b545e012d041	236	return 1;
DaveStyles	0:b545e012d041	237	}
DaveStyles	0:b545e012d041	238
DaveStyles	0:b545e012d041	239	// wait for write to finish
DaveStyles	0:b545e012d041	240	while(_spi.write(0xFF) == 0);
DaveStyles	0:b545e012d041	241
DaveStyles	0:b545e012d041	242	_cs = 1;
DaveStyles	0:b545e012d041	243	return 0;
DaveStyles	0:b545e012d041	244	}
DaveStyles	0:b545e012d041	245
DaveStyles	0:b545e012d041	246	static int ext_bits(char *data, int msb, int lsb) {
DaveStyles	0:b545e012d041	247	int bits = 0;
DaveStyles	0:b545e012d041	248	int size = 1 + msb - lsb;
DaveStyles	0:b545e012d041	249	for(int i=0; i<size; i++) {
DaveStyles	0:b545e012d041	250	int position = lsb + i;
DaveStyles	0:b545e012d041	251	int byte = 15 - (position >> 3);
DaveStyles	0:b545e012d041	252	int bit = position & 0x7;
DaveStyles	0:b545e012d041	253	int value = (data[byte] >> bit) & 1;
DaveStyles	0:b545e012d041	254	bits \|= value << i;
DaveStyles	0:b545e012d041	255	}
DaveStyles	0:b545e012d041	256	return bits;
DaveStyles	0:b545e012d041	257	}
DaveStyles	0:b545e012d041	258
DaveStyles	0:b545e012d041	259	int SDFileSystem::_sd_sectors() {
DaveStyles	0:b545e012d041	260
DaveStyles	0:b545e012d041	261	// CMD9, Response R2 (R1 byte + 16-byte block read)
DaveStyles	0:b545e012d041	262	if(_cmd(9, 0) != 0) {
DaveStyles	0:b545e012d041	263	fprintf(stderr, "Didn't get a response from the disk\n");
DaveStyles	0:b545e012d041	264	return 0;
DaveStyles	0:b545e012d041	265	}
DaveStyles	0:b545e012d041	266
DaveStyles	0:b545e012d041	267	char csd[16];
DaveStyles	0:b545e012d041	268	if(_read(csd, 16) != 0) {
DaveStyles	0:b545e012d041	269	fprintf(stderr, "Couldn't read csd response from disk\n");
DaveStyles	0:b545e012d041	270	return 0;
DaveStyles	0:b545e012d041	271	}
DaveStyles	0:b545e012d041	272
DaveStyles	0:b545e012d041	273	// csd_structure : csd[127:126]
DaveStyles	0:b545e012d041	274	// c_size : csd[73:62]
DaveStyles	0:b545e012d041	275	// c_size_mult : csd[49:47]
DaveStyles	0:b545e012d041	276	// read_bl_len : csd[83:80]
DaveStyles	0:b545e012d041	277
DaveStyles	0:b545e012d041	278	int csd_structure = ext_bits(csd, 127, 126);
DaveStyles	0:b545e012d041	279	int c_size = ext_bits(csd, 73, 62);
DaveStyles	0:b545e012d041	280	int c_size_mult = ext_bits(csd, 49, 47);
DaveStyles	0:b545e012d041	281	int read_bl_len = ext_bits(csd, 83, 80);
DaveStyles	0:b545e012d041	282
DaveStyles	0:b545e012d041	283	if(csd_structure != 0) {
DaveStyles	0:b545e012d041	284	fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
DaveStyles	0:b545e012d041	285	return 0;
DaveStyles	0:b545e012d041	286	}
DaveStyles	0:b545e012d041	287
DaveStyles	0:b545e012d041	288	int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
DaveStyles	0:b545e012d041	289	int block_size = 1 << read_bl_len;
DaveStyles	0:b545e012d041	290
DaveStyles	0:b545e012d041	291	if(block_size != 512) {
DaveStyles	0:b545e012d041	292	fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
DaveStyles	0:b545e012d041	293	return 0;
DaveStyles	0:b545e012d041	294	}
DaveStyles	0:b545e012d041	295
DaveStyles	0:b545e012d041	296	return blocks;
DaveStyles	0:b545e012d041	297	}

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	25 Nov 2009
Imports:	7
Forks:	0
Commits:	1
Dependents:	0
Dependencies:	1
Followers:	1

SDFileSystem.cpp@0:b545e012d041, 2009-11-25 (annotated)

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