LCD - testing TextLCD and SD card

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testing TextLCD and SD card

SDFileSystem.cpp@1:60d8589343b6, 2010-07-01 (annotated)

Committer:: funax
Date:: Thu Jul 01 18:04:37 2010 +0000
Revision:: 1:60d8589343b6
Parent:: 0:cc883de36463

Who changed what in which revision?

User	Revision	Line number	New contents of line
funax	0:cc883de36463	1	/* mbed Microcontroller Library - SDFileSystem
funax	0:cc883de36463	2	* Copyright (c) 2008-2009, sford
funax	0:cc883de36463	3	*
funax	0:cc883de36463	4	* Introduction
funax	0:cc883de36463	5	* ------------
funax	0:cc883de36463	6	* SD and MMC cards support a number of interfaces, but common to them all
funax	0:cc883de36463	7	* is one based on SPI. This is the one I'm implmenting because it means
funax	0:cc883de36463	8	* it is much more portable even though not so performant, and we already
funax	0:cc883de36463	9	* have the mbed SPI Interface!
funax	0:cc883de36463	10	*
funax	0:cc883de36463	11	* The main reference I'm using is Chapter 7, "SPI Mode" of:
funax	0:cc883de36463	12	* http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
funax	0:cc883de36463	13	*
funax	0:cc883de36463	14	* SPI Startup
funax	0:cc883de36463	15	* -----------
funax	0:cc883de36463	16	* The SD card powers up in SD mode. The SPI interface mode is selected by
funax	0:cc883de36463	17	* asserting CS low and sending the reset command (CMD0). The card will
funax	0:cc883de36463	18	* respond with a (R1) response.
funax	0:cc883de36463	19	*
funax	0:cc883de36463	20	* CMD8 is optionally sent to determine the voltage range supported, and
funax	0:cc883de36463	21	* indirectly determine whether it is a version 1.x SD/non-SD card or
funax	0:cc883de36463	22	* version 2.x. I'll just ignore this for now.
funax	0:cc883de36463	23	*
funax	0:cc883de36463	24	* ACMD41 is repeatedly issued to initialise the card, until "in idle"
funax	0:cc883de36463	25	* (bit 0) of the R1 response goes to '0', indicating it is initialised.
funax	0:cc883de36463	26	*
funax	0:cc883de36463	27	* You should also indicate whether the host supports High Capicity cards,
funax	0:cc883de36463	28	* and check whether the card is high capacity - i'll also ignore this
funax	0:cc883de36463	29	*
funax	0:cc883de36463	30	* SPI Protocol
funax	0:cc883de36463	31	* ------------
funax	0:cc883de36463	32	* The SD SPI protocol is based on transactions made up of 8-bit words, with
funax	0:cc883de36463	33	* the host starting every bus transaction by asserting the CS signal low. The
funax	0:cc883de36463	34	* card always responds to commands, data blocks and errors.
funax	0:cc883de36463	35	*
funax	0:cc883de36463	36	* The protocol supports a CRC, but by default it is off (except for the
funax	0:cc883de36463	37	* first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
funax	0:cc883de36463	38	* I'll leave the CRC off I think!
funax	0:cc883de36463	39	*
funax	0:cc883de36463	40	* Standard capacity cards have variable data block sizes, whereas High
funax	0:cc883de36463	41	* Capacity cards fix the size of data block to 512 bytes. I'll therefore
funax	0:cc883de36463	42	* just always use the Standard Capacity cards with a block size of 512 bytes.
funax	0:cc883de36463	43	* This is set with CMD16.
funax	0:cc883de36463	44	*
funax	0:cc883de36463	45	* You can read and write single blocks (CMD17, CMD25) or multiple blocks
funax	0:cc883de36463	46	* (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
funax	0:cc883de36463	47	* the card gets a read command, it responds with a response token, and then
funax	0:cc883de36463	48	* a data token or an error.
funax	0:cc883de36463	49	*
funax	0:cc883de36463	50	* SPI Command Format
funax	0:cc883de36463	51	* ------------------
funax	0:cc883de36463	52	* Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
funax	0:cc883de36463	53	*
funax	0:cc883de36463	54	* +---------------+------------+------------+-----------+----------+--------------+
funax	0:cc883de36463	55	* \| 01 \| cmd[5:0] \| arg[31:24] \| arg[23:16] \| arg[15:8] \| arg[7:0] \| crc[6:0] \| 1 \|
funax	0:cc883de36463	56	* +---------------+------------+------------+-----------+----------+--------------+
funax	0:cc883de36463	57	*
funax	0:cc883de36463	58	* As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
funax	0:cc883de36463	59	*
funax	0:cc883de36463	60	* All Application Specific commands shall be preceded with APP_CMD (CMD55).
funax	0:cc883de36463	61	*
funax	0:cc883de36463	62	* SPI Response Format
funax	0:cc883de36463	63	* -------------------
funax	0:cc883de36463	64	* The main response format (R1) is a status byte (normally zero). Key flags:
funax	0:cc883de36463	65	* idle - 1 if the card is in an idle state/initialising
funax	0:cc883de36463	66	* cmd - 1 if an illegal command code was detected
funax	0:cc883de36463	67	*
funax	0:cc883de36463	68	* +-------------------------------------------------+
funax	0:cc883de36463	69	* R1 \| 0 \| arg \| addr \| seq \| crc \| cmd \| erase \| idle \|
funax	0:cc883de36463	70	* +-------------------------------------------------+
funax	0:cc883de36463	71	*
funax	0:cc883de36463	72	* R1b is the same, except it is followed by a busy signal (zeros) until
funax	0:cc883de36463	73	* the first non-zero byte when it is ready again.
funax	0:cc883de36463	74	*
funax	0:cc883de36463	75	* Data Response Token
funax	0:cc883de36463	76	* -------------------
funax	0:cc883de36463	77	* Every data block written to the card is acknowledged by a byte
funax	0:cc883de36463	78	* response token
funax	0:cc883de36463	79	*
funax	0:cc883de36463	80	* +----------------------+
funax	0:cc883de36463	81	* \| xxx \| 0 \| status \| 1 \|
funax	0:cc883de36463	82	* +----------------------+
funax	0:cc883de36463	83	* 010 - OK!
funax	0:cc883de36463	84	* 101 - CRC Error
funax	0:cc883de36463	85	* 110 - Write Error
funax	0:cc883de36463	86	*
funax	0:cc883de36463	87	* Single Block Read and Write
funax	0:cc883de36463	88	* ---------------------------
funax	0:cc883de36463	89	*
funax	0:cc883de36463	90	* Block transfers have a byte header, followed by the data, followed
funax	0:cc883de36463	91	* by a 16-bit CRC. In our case, the data will always be 512 bytes.
funax	0:cc883de36463	92	*
funax	0:cc883de36463	93	* +------+---------+---------+- - - -+---------+-----------+----------+
funax	0:cc883de36463	94	* \| 0xFE \| data[0] \| data[1] \| \| data[n] \| crc[15:8] \| crc[7:0] \|
funax	0:cc883de36463	95	* +------+---------+---------+- - - -+---------+-----------+----------+
funax	0:cc883de36463	96	*/
funax	0:cc883de36463	97
funax	0:cc883de36463	98	#include "SDFileSystem.h"
funax	0:cc883de36463	99
funax	0:cc883de36463	100	#define SD_COMMAND_TIMEOUT 5000
funax	0:cc883de36463	101
funax	0:cc883de36463	102	SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
funax	0:cc883de36463	103	FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
funax	0:cc883de36463	104	_cs = 1;
funax	0:cc883de36463	105	}
funax	0:cc883de36463	106
funax	0:cc883de36463	107	int SDFileSystem::disk_initialize() {
funax	0:cc883de36463	108
funax	0:cc883de36463	109	_spi.frequency(100000); // Set to 100kHz for initialisation
funax	0:cc883de36463	110
funax	0:cc883de36463	111	// Initialise the card by clocking it a bit (cs = 1)
funax	0:cc883de36463	112	for(int i=0; i<16; i++) {
funax	0:cc883de36463	113	_spi.write(0xFF);
funax	0:cc883de36463	114	}
funax	0:cc883de36463	115
funax	0:cc883de36463	116	// send CMD0, should return with all zeros except IDLE STATE set (bit 0)
funax	0:cc883de36463	117	if(_cmd(0, 0) != 0x01) {
funax	0:cc883de36463	118	fprintf(stderr, "Not in idle state\n");
funax	0:cc883de36463	119	return 1;
funax	0:cc883de36463	120	}
funax	0:cc883de36463	121
funax	0:cc883de36463	122	// ACMD41 to give host capacity support (repeat until not busy)
funax	0:cc883de36463	123	// ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
funax	0:cc883de36463	124	for(int i=0;; i++) {
funax	0:cc883de36463	125	_cmd(55, 0);
funax	0:cc883de36463	126	int response = _cmd(41, 0);
funax	0:cc883de36463	127	if(response == 0) {
funax	0:cc883de36463	128	break;
funax	0:cc883de36463	129	} else if(i > SD_COMMAND_TIMEOUT) {
funax	0:cc883de36463	130	fprintf(stderr, "Timeout waiting for card\n");
funax	0:cc883de36463	131	return 1;
funax	0:cc883de36463	132	}
funax	0:cc883de36463	133	}
funax	0:cc883de36463	134
funax	0:cc883de36463	135	_sectors = _sd_sectors();
funax	0:cc883de36463	136
funax	0:cc883de36463	137	// Set block length to 512 (CMD16)
funax	0:cc883de36463	138	if(_cmd(16, 512) != 0) {
funax	0:cc883de36463	139	fprintf(stderr, "Set block timeout\n");
funax	0:cc883de36463	140	return 1;
funax	0:cc883de36463	141	}
funax	0:cc883de36463	142
funax	0:cc883de36463	143	_spi.frequency(1000000); // Set to 1MHz for data transfer
funax	0:cc883de36463	144	return 0;
funax	0:cc883de36463	145	}
funax	0:cc883de36463	146
funax	0:cc883de36463	147	int SDFileSystem::disk_write(const char *buffer, int block_number) {
funax	0:cc883de36463	148	// set write address for single block (CMD24)
funax	0:cc883de36463	149	if(_cmd(24, block_number * 512) != 0) {
funax	0:cc883de36463	150	return 1;
funax	0:cc883de36463	151	}
funax	0:cc883de36463	152
funax	0:cc883de36463	153	// send the data block
funax	0:cc883de36463	154	_write(buffer, 512);
funax	0:cc883de36463	155	return 0;
funax	0:cc883de36463	156	}
funax	0:cc883de36463	157
funax	0:cc883de36463	158	int SDFileSystem::disk_read(char *buffer, int block_number) {
funax	0:cc883de36463	159	// set read address for single block (CMD17)
funax	0:cc883de36463	160	if(_cmd(17, block_number * 512) != 0) {
funax	0:cc883de36463	161	return 1;
funax	0:cc883de36463	162	}
funax	0:cc883de36463	163
funax	0:cc883de36463	164	// receive the data
funax	0:cc883de36463	165	_read(buffer, 512);
funax	0:cc883de36463	166	return 0;
funax	0:cc883de36463	167	}
funax	0:cc883de36463	168
funax	0:cc883de36463	169	int SDFileSystem::disk_status() { return 0; }
funax	0:cc883de36463	170	int SDFileSystem::disk_sync() { return 0; }
funax	0:cc883de36463	171	int SDFileSystem::disk_sectors() { return _sectors; }
funax	0:cc883de36463	172
funax	0:cc883de36463	173	// PRIVATE FUNCTIONS
funax	0:cc883de36463	174
funax	0:cc883de36463	175	int SDFileSystem::_cmd(int cmd, int arg) {
funax	0:cc883de36463	176	_cs = 0;
funax	0:cc883de36463	177
funax	0:cc883de36463	178	// send a command
funax	0:cc883de36463	179	_spi.write(0x40 \| cmd);
funax	0:cc883de36463	180	_spi.write(arg >> 24);
funax	0:cc883de36463	181	_spi.write(arg >> 16);
funax	0:cc883de36463	182	_spi.write(arg >> 8);
funax	0:cc883de36463	183	_spi.write(arg >> 0);
funax	0:cc883de36463	184	_spi.write(0x95);
funax	0:cc883de36463	185
funax	0:cc883de36463	186	// wait for the repsonse (response[7] == 0)
funax	0:cc883de36463	187	for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
funax	0:cc883de36463	188	int response = _spi.write(0xFF);
funax	0:cc883de36463	189	if(!(response & 0x80)) {
funax	0:cc883de36463	190	_cs = 1;
funax	0:cc883de36463	191	return response;
funax	0:cc883de36463	192	}
funax	0:cc883de36463	193	}
funax	0:cc883de36463	194	_cs = 1;
funax	0:cc883de36463	195	return -1; // timeout
funax	0:cc883de36463	196	}
funax	0:cc883de36463	197
funax	0:cc883de36463	198	int SDFileSystem::_read(char *buffer, int length) {
funax	0:cc883de36463	199	_cs = 0;
funax	0:cc883de36463	200
funax	0:cc883de36463	201	// read until start byte (0xFF)
funax	0:cc883de36463	202	while(_spi.write(0xFF) != 0xFE);
funax	0:cc883de36463	203
funax	0:cc883de36463	204	// read data
funax	0:cc883de36463	205	for(int i=0; i<length; i++) {
funax	0:cc883de36463	206	buffer[i] = _spi.write(0xFF);
funax	0:cc883de36463	207	}
funax	0:cc883de36463	208	_spi.write(0xFF); // checksum
funax	0:cc883de36463	209	_spi.write(0xFF);
funax	0:cc883de36463	210
funax	0:cc883de36463	211	_cs = 1;
funax	0:cc883de36463	212	return 0;
funax	0:cc883de36463	213	}
funax	0:cc883de36463	214
funax	0:cc883de36463	215	int SDFileSystem::_write(const char *buffer, int length) {
funax	0:cc883de36463	216	_cs = 0;
funax	0:cc883de36463	217
funax	0:cc883de36463	218	// indicate start of block
funax	0:cc883de36463	219	_spi.write(0xFE);
funax	0:cc883de36463	220
funax	0:cc883de36463	221	// write the data
funax	0:cc883de36463	222	for(int i=0; i<length; i++) {
funax	0:cc883de36463	223	_spi.write(buffer[i]);
funax	0:cc883de36463	224	}
funax	0:cc883de36463	225
funax	0:cc883de36463	226	// write the checksum
funax	0:cc883de36463	227	_spi.write(0xFF);
funax	0:cc883de36463	228	_spi.write(0xFF);
funax	0:cc883de36463	229
funax	0:cc883de36463	230	// check the repsonse token
funax	0:cc883de36463	231	if((_spi.write(0xFF) & 0x1F) != 0x05) {
funax	0:cc883de36463	232	_cs = 1;
funax	0:cc883de36463	233	return 1;
funax	0:cc883de36463	234	}
funax	0:cc883de36463	235
funax	0:cc883de36463	236	// wait for write to finish
funax	0:cc883de36463	237	while(_spi.write(0xFF) == 0);
funax	0:cc883de36463	238
funax	0:cc883de36463	239	_cs = 1;
funax	0:cc883de36463	240	return 0;
funax	0:cc883de36463	241	}
funax	0:cc883de36463	242
funax	0:cc883de36463	243	static int ext_bits(char *data, int msb, int lsb) {
funax	0:cc883de36463	244	int bits = 0;
funax	0:cc883de36463	245	int size = 1 + msb - lsb;
funax	0:cc883de36463	246	for(int i=0; i<size; i++) {
funax	0:cc883de36463	247	int position = lsb + i;
funax	0:cc883de36463	248	int byte = 15 - (position >> 3);
funax	0:cc883de36463	249	int bit = position & 0x7;
funax	0:cc883de36463	250	int value = (data[byte] >> bit) & 1;
funax	0:cc883de36463	251	bits \|= value << i;
funax	0:cc883de36463	252	}
funax	0:cc883de36463	253	return bits;
funax	0:cc883de36463	254	}
funax	0:cc883de36463	255
funax	0:cc883de36463	256	int SDFileSystem::_sd_sectors() {
funax	0:cc883de36463	257
funax	0:cc883de36463	258	// CMD9, Response R2 (R1 byte + 16-byte block read)
funax	0:cc883de36463	259	if(_cmd(9, 0) != 0) {
funax	0:cc883de36463	260	fprintf(stderr, "Didn't get a response from the disk\n");
funax	0:cc883de36463	261	return 0;
funax	0:cc883de36463	262	}
funax	0:cc883de36463	263
funax	0:cc883de36463	264	char csd[16];
funax	0:cc883de36463	265	if(_read(csd, 16) != 0) {
funax	0:cc883de36463	266	fprintf(stderr, "Couldn't read csd response from disk\n");
funax	0:cc883de36463	267	return 0;
funax	0:cc883de36463	268	}
funax	0:cc883de36463	269
funax	0:cc883de36463	270	// csd_structure : csd[127:126]
funax	0:cc883de36463	271	// c_size : csd[73:62]
funax	0:cc883de36463	272	// c_size_mult : csd[49:47]
funax	0:cc883de36463	273	// read_bl_len : csd[83:80]
funax	0:cc883de36463	274
funax	0:cc883de36463	275	int csd_structure = ext_bits(csd, 127, 126);
funax	0:cc883de36463	276	int c_size = ext_bits(csd, 73, 62);
funax	0:cc883de36463	277	int c_size_mult = ext_bits(csd, 49, 47);
funax	0:cc883de36463	278	int read_bl_len = ext_bits(csd, 83, 80);
funax	0:cc883de36463	279
funax	0:cc883de36463	280	if(csd_structure != 0) {
funax	0:cc883de36463	281	fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
funax	0:cc883de36463	282	return 0;
funax	0:cc883de36463	283	}
funax	0:cc883de36463	284
funax	0:cc883de36463	285	int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
funax	0:cc883de36463	286	int block_size = 1 << read_bl_len;
funax	0:cc883de36463	287
funax	0:cc883de36463	288	if(block_size != 512) {
funax	0:cc883de36463	289	fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
funax	0:cc883de36463	290	return 0;
funax	0:cc883de36463	291	}
funax	0:cc883de36463	292
funax	0:cc883de36463	293	return blocks;
funax	0:cc883de36463	294	}

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	01 Jul 2010
Imports:	22
Forks:	0
Commits:	2
Dependents:	0
Dependencies:	1
Followers:	2

SDFileSystem.cpp@1:60d8589343b6, 2010-07-01 (annotated)

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