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A simple digital lock with attempted audio guidance
Dependencies: FATFileSystem TextLCD mbed
Fork of Digital_Lock_with_audio by
SDFileSystem.cpp
- Committer:
- kit2
- Date:
- 2013-04-23
- Revision:
- 1:85eb1c94154a
File content as of revision 1:85eb1c94154a:
/* 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 with cs = 1 _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; _spi.write(0xFF); return response; } } _cs = 1; _spi.write(0xFF); 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; _spi.write(0xFF); 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; _spi.write(0xFF); return 1; } // wait for write to finish while(_spi.write(0xFF) == 0); _cs = 1; _spi.write(0xFF); 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; }