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Simon Ford / Mbed 2 deprecated SDCardTest

SDFileSystem.cpp@0:666a082cf50f, 2009-11-19 (annotated)

Committer:: simon
Date:: Thu Nov 19 14:04:44 2009 +0000
Revision:: 0:666a082cf50f
Child:: 1:2dec995d53f8

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	0:666a082cf50f	1	/* mbed Microcontroller Library - SDFileSystem
simon	0:666a082cf50f	2	* Copyright (c) 2008-2009, sford
simon	0:666a082cf50f	3	*
simon	0:666a082cf50f	4	* Introduction
simon	0:666a082cf50f	5	* ------------
simon	0:666a082cf50f	6	* SD and MMC cards support a number of interfaces, but common to them all
simon	0:666a082cf50f	7	* is one based on SPI. This is the one I'm implmenting because it means
simon	0:666a082cf50f	8	* it is much more portable even though not so performant, and we already
simon	0:666a082cf50f	9	* have the mbed SPI Interface!
simon	0:666a082cf50f	10	*
simon	0:666a082cf50f	11	* The main reference I'm using is Chapter 7, "SPI Mode" of:
simon	0:666a082cf50f	12	* http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
simon	0:666a082cf50f	13	*
simon	0:666a082cf50f	14	* SPI Startup
simon	0:666a082cf50f	15	* -----------
simon	0:666a082cf50f	16	* The SD card powers up in SD mode. The SPI interface mode is selected by
simon	0:666a082cf50f	17	* asserting CS low and sending the reset command (CMD0). The card will
simon	0:666a082cf50f	18	* respond with a (R1) response.
simon	0:666a082cf50f	19	*
simon	0:666a082cf50f	20	* CMD8 is optionally sent to determine the voltage range supported, and
simon	0:666a082cf50f	21	* indirectly determine whether it is a version 1.x SD/non-SD card or
simon	0:666a082cf50f	22	* version 2.x. I'll just ignore this for now.
simon	0:666a082cf50f	23	*
simon	0:666a082cf50f	24	* ACMD41 is repeatedly issued to initialise the card, until "in idle"
simon	0:666a082cf50f	25	* (bit 0) of the R1 response goes to '0', indicating it is initialised.
simon	0:666a082cf50f	26	*
simon	0:666a082cf50f	27	* You should also indicate whether the host supports High Capicity cards,
simon	0:666a082cf50f	28	* and check whether the card is high capacity - i'll also ignore this
simon	0:666a082cf50f	29	*
simon	0:666a082cf50f	30	* SPI Protocol
simon	0:666a082cf50f	31	* ------------
simon	0:666a082cf50f	32	* The SD SPI protocol is based on transactions made up of 8-bit words, with
simon	0:666a082cf50f	33	* the host starting every bus transaction by asserting the CS signal low. The
simon	0:666a082cf50f	34	* card always responds to commands, data blocks and errors.
simon	0:666a082cf50f	35	*
simon	0:666a082cf50f	36	* The protocol supports a CRC, but by default it is off (except for the
simon	0:666a082cf50f	37	* first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
simon	0:666a082cf50f	38	* I'll leave the CRC off I think!
simon	0:666a082cf50f	39	*
simon	0:666a082cf50f	40	* Standard capacity cards have variable data block sizes, whereas High
simon	0:666a082cf50f	41	* Capacity cards fix the size of data block to 512 bytes. I'll therefore
simon	0:666a082cf50f	42	* just always use the Standard Capacity cards with a block size of 512 bytes.
simon	0:666a082cf50f	43	* This is set with CMD16.
simon	0:666a082cf50f	44	*
simon	0:666a082cf50f	45	* You can read and write single blocks (CMD17, CMD25) or multiple blocks
simon	0:666a082cf50f	46	* (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
simon	0:666a082cf50f	47	* the card gets a read command, it responds with a response token, and then
simon	0:666a082cf50f	48	* a data token or an error.
simon	0:666a082cf50f	49	*
simon	0:666a082cf50f	50	* SPI Command Format
simon	0:666a082cf50f	51	* ------------------
simon	0:666a082cf50f	52	* Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
simon	0:666a082cf50f	53	*
simon	0:666a082cf50f	54	* +---------------+------------+------------+-----------+----------+--------------+
simon	0:666a082cf50f	55	* \| 01 \| cmd[5:0] \| arg[31:24] \| arg[23:16] \| arg[15:8] \| arg[7:0] \| crc[6:0] \| 1 \|
simon	0:666a082cf50f	56	* +---------------+------------+------------+-----------+----------+--------------+
simon	0:666a082cf50f	57	*
simon	0:666a082cf50f	58	* As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
simon	0:666a082cf50f	59	*
simon	0:666a082cf50f	60	* All Application Specific commands shall be preceded with APP_CMD (CMD55).
simon	0:666a082cf50f	61	*
simon	0:666a082cf50f	62	* SPI Response Format
simon	0:666a082cf50f	63	* -------------------
simon	0:666a082cf50f	64	* The main response format (R1) is a status byte (normally zero). Key flags:
simon	0:666a082cf50f	65	* idle - 1 if the card is in an idle state/initialising
simon	0:666a082cf50f	66	* cmd - 1 if an illegal command code was detected
simon	0:666a082cf50f	67	*
simon	0:666a082cf50f	68	* +-------------------------------------------------+
simon	0:666a082cf50f	69	* R1 \| 0 \| arg \| addr \| seq \| crc \| cmd \| erase \| idle \|
simon	0:666a082cf50f	70	* +-------------------------------------------------+
simon	0:666a082cf50f	71	*
simon	0:666a082cf50f	72	* R1b is the same, except it is followed by a busy signal (zeros) until
simon	0:666a082cf50f	73	* the first non-zero byte when it is ready again.
simon	0:666a082cf50f	74	*
simon	0:666a082cf50f	75	* Data Response Token
simon	0:666a082cf50f	76	* -------------------
simon	0:666a082cf50f	77	* Every data block written to the card is acknowledged by a byte
simon	0:666a082cf50f	78	* response token
simon	0:666a082cf50f	79	*
simon	0:666a082cf50f	80	* +----------------------+
simon	0:666a082cf50f	81	* \| xxx \| 0 \| status \| 1 \|
simon	0:666a082cf50f	82	* +----------------------+
simon	0:666a082cf50f	83	* 010 - OK!
simon	0:666a082cf50f	84	* 101 - CRC Error
simon	0:666a082cf50f	85	* 110 - Write Error
simon	0:666a082cf50f	86	*
simon	0:666a082cf50f	87	* Single Block Read and Write
simon	0:666a082cf50f	88	* ---------------------------
simon	0:666a082cf50f	89	*
simon	0:666a082cf50f	90	* Block transfers have a byte header, followed by the data, followed
simon	0:666a082cf50f	91	* by a 16-bit CRC. In our case, the data will always be 512 bytes.
simon	0:666a082cf50f	92	*
simon	0:666a082cf50f	93	* +------+---------+---------+- - - -+---------+-----------+----------+
simon	0:666a082cf50f	94	* \| 0xFE \| data[0] \| data[1] \| \| data[n] \| crc[15:8] \| crc[7:0] \|
simon	0:666a082cf50f	95	* +------+---------+---------+- - - -+---------+-----------+----------+
simon	0:666a082cf50f	96	*/
simon	0:666a082cf50f	97
simon	0:666a082cf50f	98	#include "SDFileSystem.h"
simon	0:666a082cf50f	99
simon	0:666a082cf50f	100	#define SD_COMMAND_TIMEOUT 5000
simon	0:666a082cf50f	101
simon	0:666a082cf50f	102	SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
simon	0:666a082cf50f	103	FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
simon	0:666a082cf50f	104	_cs = 1;
simon	0:666a082cf50f	105	}
simon	0:666a082cf50f	106
simon	0:666a082cf50f	107	int SDFileSystem::disk_initialize() {
simon	0:666a082cf50f	108
simon	0:666a082cf50f	109	_spi.frequency(100000); // Set to 100kHz for initialisation
simon	0:666a082cf50f	110
simon	0:666a082cf50f	111	// Initialise the card by clocking it a bit (cs = 1)
simon	0:666a082cf50f	112	for(int i=0; i<16; i++) {
simon	0:666a082cf50f	113	_spi.write(0xFF);
simon	0:666a082cf50f	114	}
simon	0:666a082cf50f	115
simon	0:666a082cf50f	116	// send CMD0, should return with all zeros except IDLE STATE set (bit 0)
simon	0:666a082cf50f	117	if(_cmd(0, 0) != 0x01) {
simon	0:666a082cf50f	118	fprintf(stderr, "Not in idle state\n");
simon	0:666a082cf50f	119	return 1;
simon	0:666a082cf50f	120	}
simon	0:666a082cf50f	121
simon	0:666a082cf50f	122	// ACMD41 to give host capacity support (repeat until not busy)
simon	0:666a082cf50f	123	// ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
simon	0:666a082cf50f	124	for(int i=0;; i++) {
simon	0:666a082cf50f	125	_cmd(55, 0);
simon	0:666a082cf50f	126	int response = _cmd(41, 0);
simon	0:666a082cf50f	127	if(response == 0) {
simon	0:666a082cf50f	128	break;
simon	0:666a082cf50f	129	} else if(i > SD_COMMAND_TIMEOUT) {
simon	0:666a082cf50f	130	fprintf(stderr, "Timeout waiting for card\n");
simon	0:666a082cf50f	131	return 1;
simon	0:666a082cf50f	132	}
simon	0:666a082cf50f	133	}
simon	0:666a082cf50f	134
simon	0:666a082cf50f	135	_sectors = _sd_sectors();
simon	0:666a082cf50f	136
simon	0:666a082cf50f	137	// Set block length to 512 (CMD16)
simon	0:666a082cf50f	138	if(_cmd(16, 512) != 0) {
simon	0:666a082cf50f	139	fprintf(stderr, "Set block timeout\n");
simon	0:666a082cf50f	140	return 1;
simon	0:666a082cf50f	141	}
simon	0:666a082cf50f	142
simon	0:666a082cf50f	143	_spi.frequency(1000000); // Set to 1MHz for data transfer
simon	0:666a082cf50f	144	return 0;
simon	0:666a082cf50f	145	}
simon	0:666a082cf50f	146
simon	0:666a082cf50f	147	int SDFileSystem::disk_write(const char *buffer, int block_number) {
simon	0:666a082cf50f	148	// set write address for single block (CMD24)
simon	0:666a082cf50f	149	if(_cmd(24, block_number * 512) != 0) {
simon	0:666a082cf50f	150	return 1;
simon	0:666a082cf50f	151	}
simon	0:666a082cf50f	152
simon	0:666a082cf50f	153	// send the data block
simon	0:666a082cf50f	154	_write(buffer, 512);
simon	0:666a082cf50f	155	return 0;
simon	0:666a082cf50f	156	}
simon	0:666a082cf50f	157
simon	0:666a082cf50f	158	int SDFileSystem::disk_read(char *buffer, int block_number) {
simon	0:666a082cf50f	159	// set read address for single block (CMD17)
simon	0:666a082cf50f	160	if(_cmd(17, block_number * 512) != 0) {
simon	0:666a082cf50f	161	return 1;
simon	0:666a082cf50f	162	}
simon	0:666a082cf50f	163
simon	0:666a082cf50f	164	// receive the data
simon	0:666a082cf50f	165	_read(buffer, 512);
simon	0:666a082cf50f	166	return 0;
simon	0:666a082cf50f	167	}
simon	0:666a082cf50f	168
simon	0:666a082cf50f	169	int SDFileSystem::disk_status() { return 0; }
simon	0:666a082cf50f	170	int SDFileSystem::disk_sync() { return 0; }
simon	0:666a082cf50f	171	int SDFileSystem::disk_sectors() { return _sectors; }
simon	0:666a082cf50f	172
simon	0:666a082cf50f	173	// PRIVATE FUNCTIONS
simon	0:666a082cf50f	174
simon	0:666a082cf50f	175	int SDFileSystem::_cmd(int cmd, int arg) {
simon	0:666a082cf50f	176	_cs = 0;
simon	0:666a082cf50f	177
simon	0:666a082cf50f	178	// send a command
simon	0:666a082cf50f	179	_spi.write(0x40 \| cmd);
simon	0:666a082cf50f	180	_spi.write(arg >> 24);
simon	0:666a082cf50f	181	_spi.write(arg >> 16);
simon	0:666a082cf50f	182	_spi.write(arg >> 8);
simon	0:666a082cf50f	183	_spi.write(arg >> 0);
simon	0:666a082cf50f	184	_spi.write(0x95);
simon	0:666a082cf50f	185
simon	0:666a082cf50f	186	// wait for the repsonse (response[7] == 0)
simon	0:666a082cf50f	187	for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
simon	0:666a082cf50f	188	int response = _spi.write(0xFF);
simon	0:666a082cf50f	189	if(!(response & 0x80)) {
simon	0:666a082cf50f	190	_cs = 1;
simon	0:666a082cf50f	191	return response;
simon	0:666a082cf50f	192	}
simon	0:666a082cf50f	193	}
simon	0:666a082cf50f	194	_cs = 1;
simon	0:666a082cf50f	195	return -1; // timeout
simon	0:666a082cf50f	196	}
simon	0:666a082cf50f	197
simon	0:666a082cf50f	198	int SDFileSystem::_read(char *buffer, int length) {
simon	0:666a082cf50f	199	_cs = 0;
simon	0:666a082cf50f	200
simon	0:666a082cf50f	201	// read until start byte (0xFF)
simon	0:666a082cf50f	202	while(_spi.write(0xFF) != 0xFE);
simon	0:666a082cf50f	203
simon	0:666a082cf50f	204	// read data
simon	0:666a082cf50f	205	for(int i=0; i<length; i++) {
simon	0:666a082cf50f	206	buffer[i] = _spi.write(0xFF);
simon	0:666a082cf50f	207	}
simon	0:666a082cf50f	208	_spi.write(0xFF); // checksum
simon	0:666a082cf50f	209	_spi.write(0xFF);
simon	0:666a082cf50f	210
simon	0:666a082cf50f	211	_cs = 1;
simon	0:666a082cf50f	212	return 0;
simon	0:666a082cf50f	213	}
simon	0:666a082cf50f	214
simon	0:666a082cf50f	215	int SDFileSystem::_write(const char *buffer, int length) {
simon	0:666a082cf50f	216	_cs = 0;
simon	0:666a082cf50f	217
simon	0:666a082cf50f	218	// indicate start of block
simon	0:666a082cf50f	219	_spi.write(0xFE);
simon	0:666a082cf50f	220
simon	0:666a082cf50f	221	// write the data
simon	0:666a082cf50f	222	for(int i=0; i<length; i++) {
simon	0:666a082cf50f	223	_spi.write(buffer[i]);
simon	0:666a082cf50f	224	}
simon	0:666a082cf50f	225
simon	0:666a082cf50f	226	// write the checksum
simon	0:666a082cf50f	227	_spi.write(0xFF);
simon	0:666a082cf50f	228	_spi.write(0xFF);
simon	0:666a082cf50f	229
simon	0:666a082cf50f	230	// check the repsonse token
simon	0:666a082cf50f	231	if((_spi.write(0xFF) & 0x1F) != 0x05) {
simon	0:666a082cf50f	232	_cs = 1;
simon	0:666a082cf50f	233	return 1;
simon	0:666a082cf50f	234	}
simon	0:666a082cf50f	235
simon	0:666a082cf50f	236	// wait for write to finish
simon	0:666a082cf50f	237	while(_spi.write(0xFF) == 0);
simon	0:666a082cf50f	238
simon	0:666a082cf50f	239	_cs = 1;
simon	0:666a082cf50f	240	return 0;
simon	0:666a082cf50f	241	}
simon	0:666a082cf50f	242
simon	0:666a082cf50f	243	static int ext_bits(char *data, int msb, int lsb) {
simon	0:666a082cf50f	244	int bits = 0;
simon	0:666a082cf50f	245	int size = 1 + msb - lsb;
simon	0:666a082cf50f	246	for(int i=0; i<size; i++) {
simon	0:666a082cf50f	247	int position = lsb + i;
simon	0:666a082cf50f	248	int byte = 15 - (position >> 3);
simon	0:666a082cf50f	249	int bit = position & 0x7;
simon	0:666a082cf50f	250	int value = (data[byte] >> bit) & 1;
simon	0:666a082cf50f	251	bits \|= value << i;
simon	0:666a082cf50f	252	}
simon	0:666a082cf50f	253	return bits;
simon	0:666a082cf50f	254	}
simon	0:666a082cf50f	255
simon	0:666a082cf50f	256	int SDFileSystem::_sd_sectors() {
simon	0:666a082cf50f	257
simon	0:666a082cf50f	258	// CMD9, Response R2 (R1 byte + 16-byte block read)
simon	0:666a082cf50f	259	if(_cmd(9, 0) != 0) {
simon	0:666a082cf50f	260	fprintf(stderr, "Didn't get a response from the disk\n");
simon	0:666a082cf50f	261	return 0;
simon	0:666a082cf50f	262	}
simon	0:666a082cf50f	263
simon	0:666a082cf50f	264	char csd[16];
simon	0:666a082cf50f	265	if(_read(csd, 16) != 0) {
simon	0:666a082cf50f	266	fprintf(stderr, "Couldn't read csd response from disk\n");
simon	0:666a082cf50f	267	return 0;
simon	0:666a082cf50f	268	}
simon	0:666a082cf50f	269
simon	0:666a082cf50f	270	// csd_structure : csd[127:126]
simon	0:666a082cf50f	271	// c_size : csd[73:62]
simon	0:666a082cf50f	272	// c_size_mult : csd[49:47]
simon	0:666a082cf50f	273	// read_bl_len : csd[83:80]
simon	0:666a082cf50f	274
simon	0:666a082cf50f	275	int csd_structure = ext_bits(csd, 127, 126);
simon	0:666a082cf50f	276	int c_size = ext_bits(csd, 73, 62);
simon	0:666a082cf50f	277	int c_size_mult = ext_bits(csd, 49, 47);
simon	0:666a082cf50f	278	int read_bl_len = ext_bits(csd, 83, 80);
simon	0:666a082cf50f	279
simon	0:666a082cf50f	280	if(csd_structure != 0) {
simon	0:666a082cf50f	281	fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
simon	0:666a082cf50f	282	return 0;
simon	0:666a082cf50f	283	}
simon	0:666a082cf50f	284
simon	0:666a082cf50f	285	int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
simon	0:666a082cf50f	286	int block_size = 1 << read_bl_len;
simon	0:666a082cf50f	287
simon	0:666a082cf50f	288	if(block_size != 512) {
simon	0:666a082cf50f	289	fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
simon	0:666a082cf50f	290	return 0;
simon	0:666a082cf50f	291	}
simon	0:666a082cf50f	292
simon	0:666a082cf50f	293	return blocks;
simon	0:666a082cf50f	294	}

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	19 Nov 2009
Imports:	678
Forks:	1
Commits:	4
Dependents:	0
Dependencies:	1
Followers:	13

SDFileSystem.cpp@0:666a082cf50f, 2009-11-19 (annotated)

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