Diff: USBMSD_BD.cpp

Revision:

4:6b2f29de40d3

Parent:

3:cce1e689c548

Child:

5:13fed87fb66f

diff -r cce1e689c548 -r 6b2f29de40d3 USBMSD_BD.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/USBMSD_BD.cpp	Fri Feb 23 23:25:58 2018 +0000
@@ -0,0 +1,163 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2012 ARM Limited
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+/* 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 "USBMSD_BD.h"
+#include "mbed_debug.h"
+
+#define SD_COMMAND_TIMEOUT 5000
+
+#define SD_DBG             0
+
+USBMSD_BD::USBMSD_BD(BlockDevice* bd, bd_size_t ssize) {
+    _bd = bd;
+    _ssize = ssize;
+    //no init
+    _status = 0x01;
+    
+//    connect();
+}
+
+int USBMSD_BD::disk_initialize() {
+    _sectors = _bd->size() / _ssize;
+    
+    // OK
+    _status = 0x00;
+    
+    return 0;
+}
+
+int USBMSD_BD::disk_write(const uint8_t* buff, uint64_t sector, uint8_t count)
+{
+    bd_addr_t addr = (bd_addr_t)sector*_ssize;
+    bd_size_t size = (bd_size_t)count*_ssize;
+    int err = _bd->program(buff, addr, size);
+    return err;
+}
+
+int USBMSD_BD::disk_read(uint8_t* buff, uint64_t sector, uint8_t count)
+{
+    bd_addr_t addr = (bd_addr_t)sector*_ssize;
+    bd_size_t size = (bd_size_t)count*_ssize;
+    int err = _bd->read(buff, addr, size);
+    return err;
+}
+
+int USBMSD_BD::disk_status() { return _status; }
+int USBMSD_BD::disk_sync() { return 0; }
+uint64_t USBMSD_BD::disk_sectors() { return _sectors; }
+uint64_t USBMSD_BD::disk_size() { return (*_bd).size(); }
+
+
+// PRIVATE FUNCTIONS
+