USB Mass Storage Device Block Device
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USBMSD_BD.cpp
00001 /* mbed Microcontroller Library 00002 * Copyright (c) 2006-2012 ARM Limited 00003 * 00004 * Permission is hereby granted, free of charge, to any person obtaining a copy 00005 * of this software and associated documentation files (the "Software"), to deal 00006 * in the Software without restriction, including without limitation the rights 00007 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 00008 * copies of the Software, and to permit persons to whom the Software is 00009 * furnished to do so, subject to the following conditions: 00010 * 00011 * The above copyright notice and this permission notice shall be included in 00012 * all copies or substantial portions of the Software. 00013 * 00014 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 00015 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 00016 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 00017 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 00018 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 00019 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 00020 * SOFTWARE. 00021 */ 00022 /* Introduction 00023 * ------------ 00024 * SD and MMC cards support a number of interfaces, but common to them all 00025 * is one based on SPI. This is the one I'm implmenting because it means 00026 * it is much more portable even though not so performant, and we already 00027 * have the mbed SPI Interface! 00028 * 00029 * The main reference I'm using is Chapter 7, "SPI Mode" of: 00030 * http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf 00031 * 00032 * SPI Startup 00033 * ----------- 00034 * The SD card powers up in SD mode. The SPI interface mode is selected by 00035 * asserting CS low and sending the reset command (CMD0). The card will 00036 * respond with a (R1) response. 00037 * 00038 * CMD8 is optionally sent to determine the voltage range supported, and 00039 * indirectly determine whether it is a version 1.x SD/non-SD card or 00040 * version 2.x. I'll just ignore this for now. 00041 * 00042 * ACMD41 is repeatedly issued to initialise the card, until "in idle" 00043 * (bit 0) of the R1 response goes to '0', indicating it is initialised. 00044 * 00045 * You should also indicate whether the host supports High Capicity cards, 00046 * and check whether the card is high capacity - i'll also ignore this 00047 * 00048 * SPI Protocol 00049 * ------------ 00050 * The SD SPI protocol is based on transactions made up of 8-bit words, with 00051 * the host starting every bus transaction by asserting the CS signal low. The 00052 * card always responds to commands, data blocks and errors. 00053 * 00054 * The protocol supports a CRC, but by default it is off (except for the 00055 * first reset CMD0, where the CRC can just be pre-calculated, and CMD8) 00056 * I'll leave the CRC off I think! 00057 * 00058 * Standard capacity cards have variable data block sizes, whereas High 00059 * Capacity cards fix the size of data block to 512 bytes. I'll therefore 00060 * just always use the Standard Capacity cards with a block size of 512 bytes. 00061 * This is set with CMD16. 00062 * 00063 * You can read and write single blocks (CMD17, CMD25) or multiple blocks 00064 * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When 00065 * the card gets a read command, it responds with a response token, and then 00066 * a data token or an error. 00067 * 00068 * SPI Command Format 00069 * ------------------ 00070 * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC. 00071 * 00072 * +---------------+------------+------------+-----------+----------+--------------+ 00073 * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 | 00074 * +---------------+------------+------------+-----------+----------+--------------+ 00075 * 00076 * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95) 00077 * 00078 * All Application Specific commands shall be preceded with APP_CMD (CMD55). 00079 * 00080 * SPI Response Format 00081 * ------------------- 00082 * The main response format (R1) is a status byte (normally zero). Key flags: 00083 * idle - 1 if the card is in an idle state/initialising 00084 * cmd - 1 if an illegal command code was detected 00085 * 00086 * +-------------------------------------------------+ 00087 * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle | 00088 * +-------------------------------------------------+ 00089 * 00090 * R1b is the same, except it is followed by a busy signal (zeros) until 00091 * the first non-zero byte when it is ready again. 00092 * 00093 * Data Response Token 00094 * ------------------- 00095 * Every data block written to the card is acknowledged by a byte 00096 * response token 00097 * 00098 * +----------------------+ 00099 * | xxx | 0 | status | 1 | 00100 * +----------------------+ 00101 * 010 - OK! 00102 * 101 - CRC Error 00103 * 110 - Write Error 00104 * 00105 * Single Block Read and Write 00106 * --------------------------- 00107 * 00108 * Block transfers have a byte header, followed by the data, followed 00109 * by a 16-bit CRC. In our case, the data will always be 512 bytes. 00110 * 00111 * +------+---------+---------+- - - -+---------+-----------+----------+ 00112 * | 0xFE | data[0] | data[1] | | data[n] | crc[15:8] | crc[7:0] | 00113 * +------+---------+---------+- - - -+---------+-----------+----------+ 00114 */ 00115 #include "USBMSD_BD.h" 00116 #include "mbed_debug.h" 00117 00118 #define SD_COMMAND_TIMEOUT 5000 00119 00120 #define SD_DBG 0 00121 00122 USBMSD_BD::USBMSD_BD(BlockDevice* bd) { 00123 _bd = bd; 00124 //no init 00125 _status = 0x01; 00126 00127 // connect(); 00128 } 00129 00130 int USBMSD_BD::disk_initialize() { 00131 _bd->init(); 00132 _ssize = _bd->get_erase_size(); 00133 _sectors = _bd->size() / _ssize; 00134 00135 // OK 00136 _status = 0x00; 00137 00138 return 0; 00139 } 00140 00141 int USBMSD_BD::disk_write(const uint8_t* buff, uint64_t sector, uint8_t count) 00142 { 00143 bd_addr_t addr = (bd_addr_t)sector*_ssize; 00144 bd_size_t size = (bd_size_t)count*_ssize; 00145 int err = _bd->erase(addr, size); 00146 err = _bd->program(buff, addr, size); 00147 return err; 00148 } 00149 00150 int USBMSD_BD::disk_read(uint8_t* buff, uint64_t sector, uint8_t count) 00151 { 00152 bd_addr_t addr = (bd_addr_t)sector*_ssize; 00153 bd_size_t size = (bd_size_t)count*_ssize; 00154 int err = _bd->read(buff, addr, size); 00155 return err; 00156 } 00157 00158 int USBMSD_BD::disk_status() { return _status; } 00159 int USBMSD_BD::disk_sync() { return 0; } 00160 uint64_t USBMSD_BD::disk_sectors() { return _sectors; } 00161 uint64_t USBMSD_BD::disk_size() { return _bd->size(); } 00162 00163 00164 // PRIVATE FUNCTIONS 00165
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