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Simon Ford / Mbed 2 deprecated SDCardTest

SDFileSystem.cpp@1:2dec995d53f8, 2009-12-14 (annotated)

Committer:: simon
Date:: Mon Dec 14 20:31:54 2009 +0000
Revision:: 1:2dec995d53f8
Parent:: 0:666a082cf50f
Child:: 2:849162a1207f

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	1:2dec995d53f8	1	/* mbed Microcontroller Library - SDFileSystem
simon	1:2dec995d53f8	2	* Copyright (c) 2008-2009, sford
simon	1:2dec995d53f8	3	*
simon	1:2dec995d53f8	4	* Introduction
simon	1:2dec995d53f8	5	* ------------
simon	1:2dec995d53f8	6	* SD and MMC cards support a number of interfaces, but common to them all
simon	1:2dec995d53f8	7	* is one based on SPI. This is the one I'm implmenting because it means
simon	1:2dec995d53f8	8	* it is much more portable even though not so performant, and we already
simon	1:2dec995d53f8	9	* have the mbed SPI Interface!
simon	1:2dec995d53f8	10	*
simon	1:2dec995d53f8	11	* The main reference I'm using is Chapter 7, "SPI Mode" of:
simon	1:2dec995d53f8	12	* http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
simon	1:2dec995d53f8	13	*
simon	1:2dec995d53f8	14	* SPI Startup
simon	1:2dec995d53f8	15	* -----------
simon	1:2dec995d53f8	16	* The SD card powers up in SD mode. The SPI interface mode is selected by
simon	1:2dec995d53f8	17	* asserting CS low and sending the reset command (CMD0). The card will
simon	1:2dec995d53f8	18	* respond with a (R1) response.
simon	1:2dec995d53f8	19	*
simon	1:2dec995d53f8	20	* CMD8 is optionally sent to determine the voltage range supported, and
simon	1:2dec995d53f8	21	* indirectly determine whether it is a version 1.x SD/non-SD card or
simon	1:2dec995d53f8	22	* version 2.x. I'll just ignore this for now.
simon	1:2dec995d53f8	23	*
simon	1:2dec995d53f8	24	* ACMD41 is repeatedly issued to initialise the card, until "in idle"
simon	1:2dec995d53f8	25	* (bit 0) of the R1 response goes to '0', indicating it is initialised.
simon	1:2dec995d53f8	26	*
simon	1:2dec995d53f8	27	* You should also indicate whether the host supports High Capicity cards,
simon	1:2dec995d53f8	28	* and check whether the card is high capacity - i'll also ignore this
simon	1:2dec995d53f8	29	*
simon	1:2dec995d53f8	30	* SPI Protocol
simon	1:2dec995d53f8	31	* ------------
simon	1:2dec995d53f8	32	* The SD SPI protocol is based on transactions made up of 8-bit words, with
simon	1:2dec995d53f8	33	* the host starting every bus transaction by asserting the CS signal low. The
simon	1:2dec995d53f8	34	* card always responds to commands, data blocks and errors.
simon	1:2dec995d53f8	35	*
simon	1:2dec995d53f8	36	* The protocol supports a CRC, but by default it is off (except for the
simon	1:2dec995d53f8	37	* first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
simon	1:2dec995d53f8	38	* I'll leave the CRC off I think!
simon	1:2dec995d53f8	39	*
simon	1:2dec995d53f8	40	* Standard capacity cards have variable data block sizes, whereas High
simon	1:2dec995d53f8	41	* Capacity cards fix the size of data block to 512 bytes. I'll therefore
simon	1:2dec995d53f8	42	* just always use the Standard Capacity cards with a block size of 512 bytes.
simon	1:2dec995d53f8	43	* This is set with CMD16.
simon	1:2dec995d53f8	44	*
simon	1:2dec995d53f8	45	* You can read and write single blocks (CMD17, CMD25) or multiple blocks
simon	1:2dec995d53f8	46	* (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
simon	1:2dec995d53f8	47	* the card gets a read command, it responds with a response token, and then
simon	1:2dec995d53f8	48	* a data token or an error.
simon	1:2dec995d53f8	49	*
simon	1:2dec995d53f8	50	* SPI Command Format
simon	1:2dec995d53f8	51	* ------------------
simon	1:2dec995d53f8	52	* Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
simon	1:2dec995d53f8	53	*
simon	1:2dec995d53f8	54	* +---------------+------------+------------+-----------+----------+--------------+
simon	1:2dec995d53f8	55	* \| 01 \| cmd[5:0] \| arg[31:24] \| arg[23:16] \| arg[15:8] \| arg[7:0] \| crc[6:0] \| 1 \|
simon	1:2dec995d53f8	56	* +---------------+------------+------------+-----------+----------+--------------+
simon	1:2dec995d53f8	57	*
simon	1:2dec995d53f8	58	* As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
simon	1:2dec995d53f8	59	*
simon	1:2dec995d53f8	60	* All Application Specific commands shall be preceded with APP_CMD (CMD55).
simon	1:2dec995d53f8	61	*
simon	1:2dec995d53f8	62	* SPI Response Format
simon	1:2dec995d53f8	63	* -------------------
simon	1:2dec995d53f8	64	* The main response format (R1) is a status byte (normally zero). Key flags:
simon	1:2dec995d53f8	65	* idle - 1 if the card is in an idle state/initialising
simon	1:2dec995d53f8	66	* cmd - 1 if an illegal command code was detected
simon	1:2dec995d53f8	67	*
simon	1:2dec995d53f8	68	* +-------------------------------------------------+
simon	1:2dec995d53f8	69	* R1 \| 0 \| arg \| addr \| seq \| crc \| cmd \| erase \| idle \|
simon	1:2dec995d53f8	70	* +-------------------------------------------------+
simon	1:2dec995d53f8	71	*
simon	1:2dec995d53f8	72	* R1b is the same, except it is followed by a busy signal (zeros) until
simon	1:2dec995d53f8	73	* the first non-zero byte when it is ready again.
simon	1:2dec995d53f8	74	*
simon	1:2dec995d53f8	75	* Data Response Token
simon	1:2dec995d53f8	76	* -------------------
simon	1:2dec995d53f8	77	* Every data block written to the card is acknowledged by a byte
simon	1:2dec995d53f8	78	* response token
simon	1:2dec995d53f8	79	*
simon	1:2dec995d53f8	80	* +----------------------+
simon	1:2dec995d53f8	81	* \| xxx \| 0 \| status \| 1 \|
simon	1:2dec995d53f8	82	* +----------------------+
simon	1:2dec995d53f8	83	* 010 - OK!
simon	1:2dec995d53f8	84	* 101 - CRC Error
simon	1:2dec995d53f8	85	* 110 - Write Error
simon	1:2dec995d53f8	86	*
simon	1:2dec995d53f8	87	* Single Block Read and Write
simon	1:2dec995d53f8	88	* ---------------------------
simon	1:2dec995d53f8	89	*
simon	1:2dec995d53f8	90	* Block transfers have a byte header, followed by the data, followed
simon	1:2dec995d53f8	91	* by a 16-bit CRC. In our case, the data will always be 512 bytes.
simon	1:2dec995d53f8	92	*
simon	1:2dec995d53f8	93	* +------+---------+---------+- - - -+---------+-----------+----------+
simon	1:2dec995d53f8	94	* \| 0xFE \| data[0] \| data[1] \| \| data[n] \| crc[15:8] \| crc[7:0] \|
simon	1:2dec995d53f8	95	* +------+---------+---------+- - - -+---------+-----------+----------+
simon	1:2dec995d53f8	96	*/
simon	1:2dec995d53f8	97
simon	1:2dec995d53f8	98	#include "SDFileSystem.h"
simon	1:2dec995d53f8	99
simon	1:2dec995d53f8	100	#define SD_COMMAND_TIMEOUT 5000
simon	1:2dec995d53f8	101
simon	1:2dec995d53f8	102	SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
simon	1:2dec995d53f8	103	FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
simon	1:2dec995d53f8	104	_cs = 1;
simon	1:2dec995d53f8	105	}
simon	1:2dec995d53f8	106
simon	1:2dec995d53f8	107	int SDFileSystem::disk_initialize() {
simon	1:2dec995d53f8	108
simon	1:2dec995d53f8	109	_spi.frequency(100000); // Set to 100kHz for initialisation
simon	1:2dec995d53f8	110
simon	1:2dec995d53f8	111	// Initialise the card by clocking it with cs = 1
simon	1:2dec995d53f8	112	_cs = 1;
simon	1:2dec995d53f8	113	for(int i=0; i<16; i++) {
simon	1:2dec995d53f8	114	_spi.write(0xFF);
simon	1:2dec995d53f8	115	}
simon	1:2dec995d53f8	116
simon	1:2dec995d53f8	117	// send CMD0, should return with all zeros except IDLE STATE set (bit 0)
simon	1:2dec995d53f8	118	if(_cmd(0, 0) != 0x01) {
simon	1:2dec995d53f8	119	fprintf(stderr, "Not in idle state\n");
simon	1:2dec995d53f8	120	return 1;
simon	1:2dec995d53f8	121	}
simon	1:2dec995d53f8	122
simon	1:2dec995d53f8	123	// ACMD41 to give host capacity support (repeat until not busy)
simon	1:2dec995d53f8	124	// ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
simon	1:2dec995d53f8	125	for(int i=0;; i++) {
simon	1:2dec995d53f8	126	_cmd(55, 0);
simon	1:2dec995d53f8	127	int response = _cmd(41, 0);
simon	1:2dec995d53f8	128	if(response == 0) {
simon	1:2dec995d53f8	129	break;
simon	1:2dec995d53f8	130	} else if(i > SD_COMMAND_TIMEOUT) {
simon	1:2dec995d53f8	131	fprintf(stderr, "Timeout waiting for card\n");
simon	1:2dec995d53f8	132	return 1;
simon	1:2dec995d53f8	133	}
simon	1:2dec995d53f8	134	}
simon	1:2dec995d53f8	135
simon	1:2dec995d53f8	136	_sectors = _sd_sectors();
simon	1:2dec995d53f8	137
simon	1:2dec995d53f8	138	// Set block length to 512 (CMD16)
simon	1:2dec995d53f8	139	if(_cmd(16, 512) != 0) {
simon	1:2dec995d53f8	140	fprintf(stderr, "Set block timeout\n");
simon	1:2dec995d53f8	141	return 1;
simon	1:2dec995d53f8	142	}
simon	1:2dec995d53f8	143
simon	1:2dec995d53f8	144	_spi.frequency(1000000); // Set to 1MHz for data transfer
simon	1:2dec995d53f8	145	return 0;
simon	1:2dec995d53f8	146	}
simon	1:2dec995d53f8	147
simon	1:2dec995d53f8	148	int SDFileSystem::disk_write(const char *buffer, int block_number) {
simon	1:2dec995d53f8	149	// set write address for single block (CMD24)
simon	1:2dec995d53f8	150	if(_cmd(24, block_number * 512) != 0) {
simon	1:2dec995d53f8	151	return 1;
simon	1:2dec995d53f8	152	}
simon	1:2dec995d53f8	153
simon	1:2dec995d53f8	154	// send the data block
simon	1:2dec995d53f8	155	_write(buffer, 512);
simon	1:2dec995d53f8	156	return 0;
simon	1:2dec995d53f8	157	}
simon	1:2dec995d53f8	158
simon	1:2dec995d53f8	159	int SDFileSystem::disk_read(char *buffer, int block_number) {
simon	1:2dec995d53f8	160	// set read address for single block (CMD17)
simon	1:2dec995d53f8	161	if(_cmd(17, block_number * 512) != 0) {
simon	1:2dec995d53f8	162	return 1;
simon	1:2dec995d53f8	163	}
simon	1:2dec995d53f8	164
simon	1:2dec995d53f8	165	// receive the data
simon	1:2dec995d53f8	166	_read(buffer, 512);
simon	1:2dec995d53f8	167	return 0;
simon	1:2dec995d53f8	168	}
simon	1:2dec995d53f8	169
simon	1:2dec995d53f8	170	int SDFileSystem::disk_status() { return 0; }
simon	1:2dec995d53f8	171	int SDFileSystem::disk_sync() { return 0; }
simon	1:2dec995d53f8	172	int SDFileSystem::disk_sectors() { return _sectors; }
simon	1:2dec995d53f8	173
simon	1:2dec995d53f8	174	// PRIVATE FUNCTIONS
simon	1:2dec995d53f8	175
simon	1:2dec995d53f8	176	int SDFileSystem::_cmd(int cmd, int arg) {
simon	1:2dec995d53f8	177	_cs = 0;
simon	1:2dec995d53f8	178
simon	1:2dec995d53f8	179	// send a command
simon	1:2dec995d53f8	180	_spi.write(0x40 \| cmd);
simon	1:2dec995d53f8	181	_spi.write(arg >> 24);
simon	1:2dec995d53f8	182	_spi.write(arg >> 16);
simon	1:2dec995d53f8	183	_spi.write(arg >> 8);
simon	1:2dec995d53f8	184	_spi.write(arg >> 0);
simon	1:2dec995d53f8	185	_spi.write(0x95);
simon	1:2dec995d53f8	186
simon	1:2dec995d53f8	187	// wait for the repsonse (response[7] == 0)
simon	1:2dec995d53f8	188	for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
simon	1:2dec995d53f8	189	int response = _spi.write(0xFF);
simon	1:2dec995d53f8	190	if(!(response & 0x80)) {
simon	1:2dec995d53f8	191	_cs = 1;
simon	1:2dec995d53f8	192	_spi.write(0xFF);
simon	1:2dec995d53f8	193	return response;
simon	1:2dec995d53f8	194	}
simon	1:2dec995d53f8	195	}
simon	1:2dec995d53f8	196	_cs = 1;
simon	1:2dec995d53f8	197	_spi.write(0xFF);
simon	1:2dec995d53f8	198	return -1; // timeout
simon	1:2dec995d53f8	199	}
simon	1:2dec995d53f8	200
simon	1:2dec995d53f8	201	int SDFileSystem::_read(char *buffer, int length) {
simon	1:2dec995d53f8	202	_cs = 0;
simon	1:2dec995d53f8	203
simon	1:2dec995d53f8	204	// read until start byte (0xFF)
simon	1:2dec995d53f8	205	while(_spi.write(0xFF) != 0xFE);
simon	1:2dec995d53f8	206
simon	1:2dec995d53f8	207	// read data
simon	1:2dec995d53f8	208	for(int i=0; i<length; i++) {
simon	1:2dec995d53f8	209	buffer[i] = _spi.write(0xFF);
simon	1:2dec995d53f8	210	}
simon	1:2dec995d53f8	211	_spi.write(0xFF); // checksum
simon	1:2dec995d53f8	212	_spi.write(0xFF);
simon	1:2dec995d53f8	213
simon	1:2dec995d53f8	214	_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	}

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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@1:2dec995d53f8, 2009-12-14 (annotated)

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