- uint8_t SD_CalcCRC7(uint64_t Bits, uint8_t BitCount)
- {
- uint8_t i = 0, CRC7 = 0, XORB = 0;
- for (i = 1; i <= BitCount; i++)
- {
- XORB = ((CRC7 >> 6) & 1) ^ ((Bits >> (BitCount - i)) & 1);
- CRC7 = (CRC7 << 1) & 0x7F;
- CRC7^= (XORB << 3) | XORB;
- }
- return (CRC7);
- }
- uint8_t SD_SendCommand(uint8_t Command, uint32_t Argument)
- {
- uint8_t CRC7 = 0, Response = 0;
- uint64_t Bits = 0;
- Bits = 0x40 + Command;
- Bits <<= 32;
- Bits |= Argument;
- CRC7 = SD_CalcCRC7(Bits, 40) << 1;
- SD_SPI_NSS_H();
- SD_SPI_ReadWriteByte(0xFF);
- SD_SPI_NSS_L();
- SD_SPI_ReadWriteByte(0x40 + Command);
- SD_SPI_ReadWriteByte(Argument >> 24);
- SD_SPI_ReadWriteByte(Argument >> 16);
- SD_SPI_ReadWriteByte(Argument >> 8);
- SD_SPI_ReadWriteByte(Argument >> 0);
- SD_SPI_ReadWriteByte(CRC7 + 1);
- do
- {
- Response = SD_SPI_ReadWriteByte(0xFF);
- } while(Response & 0x80);
- return (Response);
- }
5.2.SPI模式下支持的命令：
这一小节可以参考《Physical Layer Simplified Specification Version 9.10》手册的7.3.1.3章节，这边就不再展开了。
5.3.SPI模式下的初始化流程
可以参考《Physical Layer Simplified Specification Version 9.10》手册的7.2.1章节
代码实现：
- uint8_t SD_Init(void)
- {
- uint8_t R7[5], OCR[4];
- SD_SPI_NSS_H();
- for(uint8_t i = 0; i < 16; i++)
- {
- SD_SPI_ReadWriteByte(0xFF);
- }
- if (SD_SendCommand(CMD0, 0x00000000) != R1_IN_IDLE_STATE)
- {
- printf("\r\n");
- printf("\r\nUnusable Card!"); return (2);
- }
- if (SD_SendCommand(CMD8, 0x000001AA) & R1_ILLEGAL_COMMAND)
- {
- printf("\r\n");
- printf("\r\nVer1.X SD Memory Card or Not SD Memory Card");
- //to do...
- }
- else
- {
- printf("\r\n");
- printf("\r\nVer2.00 or later SD Memory Card");
- R7[1] = SD_SPI_ReadWriteByte(0xFF);
- R7[2] = SD_SPI_ReadWriteByte(0xFF);
- R7[3] = SD_SPI_ReadWriteByte(0xFF);
- R7[4] = SD_SPI_ReadWriteByte(0xFF);
- if ((R7[3] == 0x01) && (R7[4] == 0xAA))
- {
- printf("\r\n");
- printf("\r\nCompatible voltage range and check pattern is corrent");
- SD_SendCommand(CMD58, 0x00000000);
- OCR[0] = SD_SPI_ReadWriteByte(0xFF);
- OCR[1] = SD_SPI_ReadWriteByte(0xFF);
- OCR[2] = SD_SPI_ReadWriteByte(0xFF);
- OCR[3] = SD_SPI_ReadWriteByte(0xFF);
- printf("\r\n");
- printf("\r\nCard power up status bit(busy) : %d", SD_GetField(OCR, sizeof(OCR), 1, 31));
- printf("\r\nCard Capacity Status(CCS) : %d", SD_GetField(OCR, sizeof(OCR), 1, 30));
- printf("\r\nUHS-II Card Status : %d", SD_GetField(OCR, sizeof(OCR), 1, 29));
- printf("\r\nOver 2TB support Status(CO2T) : %d", SD_GetField(OCR, sizeof(OCR), 1, 27));
- printf("\r\nSwitch to 1.8V Accepted(S18A) : %d", SD_GetField(OCR, sizeof(OCR), 1, 24));
- printf("\r\nVDD Voltage Window : %x", SD_GetField(OCR, sizeof(OCR), 9, 15));
- JMP_ACMD41:
- if (SD_SendCommand(CMD55, 0x00000000) == R1_IN_IDLE_STATE)
- {
- if (SD_SendCommand(ACMD41, 1UL << 30) == R1_IN_IDLE_STATE)
- {
- goto JMP_ACMD41;
- }
- else
- {
- SD_SendCommand(CMD58, 0x00000000);
- OCR[0] = SD_SPI_ReadWriteByte(0xFF);
- OCR[1] = SD_SPI_ReadWriteByte(0xFF);
- OCR[2] = SD_SPI_ReadWriteByte(0xFF);
- OCR[3] = SD_SPI_ReadWriteByte(0xFF);
- printf("\r\n");
- printf("\r\nCard power up status bit(busy) : %d", SD_GetField(OCR, sizeof(OCR), 1, 31));
- printf("\r\nCard Capacity Status(CCS) : %d", SD_GetField(OCR, sizeof(OCR), 1, 30));
- printf("\r\nUHS-II Card Status : %d", SD_GetField(OCR, sizeof(OCR), 1, 29));
- printf("\r\nOver 2TB support Status(CO2T) : %d", SD_GetField(OCR, sizeof(OCR), 1, 27));
- printf("\r\nSwitch to 1.8V Accepted(S18A) : %d", SD_GetField(OCR, sizeof(OCR), 1, 24));
- printf("\r\nVDD Voltage Window : %x", SD_GetField(OCR, sizeof(OCR), 9, 15));
- if (SD_GetField(OCR, sizeof(OCR), 1, 30) != 0)
- {
- printf("\r\n");
- printf("\r\nVer2.00 or later High Capacity or Extended Capacity SD Memory Card");
- }
- else
- {
- printf("\r\n");
- printf("\r\nVer2.00 or later Standard Capacity SD Memory Card");
- }
- }
- }
- else
- {
- goto JMP_ACMD41;
- }
- }
- else
- {
- printf("\r\n");
- printf("\r\nUnusable Card!"); return (1);
- }
- }
- SDGetCID();
- SDGetCSD();
- return (0);
- }
运行结果：
5.4.获取SD卡CID信息：
可以参考《Physical Layer Simplified Specification Version 9.10》手册的5.2章节
代码实现：
- void SDGetCID(void)
- {
- uint8_t CID[16], R1 = 0;
- R1 = SD_SendCommand(CMD10, 0x00000000);
- while (SD_SPI_ReadWriteByte(0xFF) != 0xFE)
- {
- __ASM("nop");
- }
- for (uint8_t i = 0; i < 16; i++)
- {
- CID[i] = SD_SPI_ReadWriteByte(0xFF);
- }
- SD_SPI_ReadWriteByte(0xFF);
- SD_SPI_ReadWriteByte(0xFF);
- printf("\r\n");
- printf("\r\n%s Response : 0x%02X", __FUNCTION__, R1);
- for (uint8_t i = 0; i < 16; i++)
- {
- if ((i % 8) == 0)
- {
- printf("\r\n");
- }
- printf("0x%02X ", CID[i]);
- }
- printf("\r\n");
- printf("\r\nManufacturer ID (MID) : 0x%02X", SD_GetField(CID, sizeof(CID), 8, 120));
- printf("\r\nOEM/Application ID (OID) : %c%c", SD_GetField(CID, sizeof(CID), 8, 112),
- SD_GetField(CID, sizeof(CID), 8, 104));
- printf("\r\nProduct name (PNM) : %c%c%c%c%c", SD_GetField(CID, sizeof(CID), 8, 96),
- SD_GetField(CID, sizeof(CID), 8, 88),
- SD_GetField(CID, sizeof(CID), 8, 80),
- SD_GetField(CID, sizeof(CID), 8, 72),
- SD_GetField(CID, sizeof(CID), 8, 64));
- printf("\r\nProduct revision (PRV) : 0x%02X", SD_GetField(CID, sizeof(CID), 8, 56));
- printf("\r\nProduct serial number (PSN) : 0x%X", SD_GetField(CID, sizeof(CID), 32, 24));
- printf("\r\nManufacturing data (MDT) : 20%02d-%d", SD_GetField(CID, sizeof(CID), 8, 12),
- SD_GetField(CID, sizeof(CID), 4, 8));
- }
运行结果：
5.5.获取SD卡CSD信息：
可以参考《Physical Layer Simplified Specification Version 9.10》手册的5.3章节，CSD有3个版本，每个版本对应的CSD各个字段的功能定义都不尽相同，如下图列举出的是实验TF卡的Version 2.0版本的CSD定义字段：
代码实现：
- uint32_t SD_GetField(uint8_t *Source, uint8_t Length, uint8_t Width, uint8_t Start)
- {
- uint32_t Value = 0, Index = 0, Offset = 0, BitValue = 0;
- for (uint8_t i = 0; i < Width; i++)
- {
- Index = (Start + i) / 8;
- Offset = (Start + i) % 8;
- BitValue = (Source[(Length - 1) - Index] >> Offset) & 1;
- Value |= BitValue << i;
- }
- return Value;
- }
- void SDGetCSD(void)
- {
- uint8_t CSD[16], R1 = 0;
- R1 = SD_SendCommand(CMD9, 0x00000000);
- while (SD_SPI_ReadWriteByte(0xFF) != 0xFE)
- {
- __ASM("nop");
- }
- for (uint8_t i = 0; i < 16; i++)
- {
- CSD[i] = SD_SPI_ReadWriteByte(0xFF);
- }
- SD_SPI_ReadWriteByte(0xFF);
- SD_SPI_ReadWriteByte(0xFF);
- printf("\r\n");
- printf("\r\n%s Response : 0x%02X", __FUNCTION__, R1);
- for (uint8_t i = 0; i < 16; i++)
- {
- if ((i % 8) == 0)
- {
- printf("\r\n");
- }
- printf("0x%02X ", CSD[i]);
- }
- printf("\r\n");
- uint32_t CSD_STRUCTURE = SD_GetField(CSD, sizeof(CSD), 2, 126);
- switch(CSD_STRUCTURE)
- {
- case 0:
- printf("\r\nCSD Version 1.0 : Standard Capacity");
- break;
- case 1:
- printf("\r\nCSD Version 2.0 : High Capacity and Extended Capacity");
- printf("\r\n");
- printf("\r\ndata read access-time (TAAC) : 0x%02X", SD_GetField(CSD, sizeof(CSD), 8, 112));
- printf("\r\ndata read access-time in CLK cycles (NSAC) : 0x%02X", SD_GetField(CSD, sizeof(CSD), 8, 104));
- printf("\r\nmax. data transfer rate (TRAN_SPEED) : 0x%02X", SD_GetField(CSD, sizeof(CSD), 8, 96));
- printf("\r\ncard command classes (CCC) : 0x%X", SD_GetField(CSD, sizeof(CSD), 12, 84));
- printf("\r\nmax. read data block length (READ_BL_LEN) : %d, %0.0f Byte", SD_GetField(CSD, sizeof(CSD), 4, 80), pow(2, SD_GetField(CSD, sizeof(CSD), 4, 80)));
- printf("\r\npartial blocks for read allowed (READ_BL_PARTIAL) : %d", SD_GetField(CSD, sizeof(CSD), 1, 79));
- printf("\r\nwrite block misalignment (WRITE_BLK_MISALIGN): %d", SD_GetField(CSD, sizeof(CSD), 1, 78));
- printf("\r\nread block misalignment (READ_BLK_MISALIGN) : %d", SD_GetField(CSD, sizeof(CSD), 1, 77));
- printf("\r\nDSR implemented (DSR_IMP) : %d", SD_GetField(CSD, sizeof(CSD), 1, 76));
- printf("\r\ndevice size (C_SIZE) : %d", SD_GetField(CSD, sizeof(CSD), 22, 48));
- printf("\r\nerase single block enable (ERASE_BLK_EN) : %d", SD_GetField(CSD, sizeof(CSD), 1, 46));
- printf("\r\nerase sector size (SECTOR_SIZE) : %d, %d KB", SD_GetField(CSD, sizeof(CSD), 7, 39), 512 * (SD_GetField(CSD, sizeof(CSD), 7, 39) + 1) / 1024);
- printf("\r\nwrite protect group size (WP_GRP_SIZE) : %d", SD_GetField(CSD, sizeof(CSD), 7, 32));
- printf("\r\nwrite protect group enable (WP_GRP_ENABLE) : %d", SD_GetField(CSD, sizeof(CSD), 1, 31));
- printf("\r\nwrite speed factor (R2W_FACTOR) : %d", SD_GetField(CSD, sizeof(CSD), 3, 26));
- printf("\r\nmax. write data block length (WRITE_BL_LEN) : %d, %0.0f Byte", SD_GetField(CSD, sizeof(CSD), 4, 22), pow(2, SD_GetField(CSD, sizeof(CSD), 4, 22)));
- printf("\r\npartial blocks for write allowed (WRITE_BL_PARTIAL) : %d", SD_GetField(CSD, sizeof(CSD), 1, 21));
- printf("\r\nFile format group (FILE_FORMAT_GRP) : %d", SD_GetField(CSD, sizeof(CSD), 1, 15));
- printf("\r\ncopy flag (COPY) : %d", SD_GetField(CSD, sizeof(CSD), 1, 14));
- printf("\r\npermanent write protection (PERM_WRITE_PROTECT): %d", SD_GetField(CSD, sizeof(CSD), 1, 13));
- printf("\r\ntemporary write protection (TMP_WRITE_PROTECT) : %d", SD_GetField(CSD, sizeof(CSD), 1, 12));
- printf("\r\nFile format (FILE_FORMAT) : %d", SD_GetField(CSD, sizeof(CSD), 2, 10));
- printf("\r\nwrite protection until power cycle (WP_UPC) : %d", SD_GetField(CSD, sizeof(CSD), 1, 9));
- printf("\r\n");
- printf("\r\nMemory capacity = (C_SIZE + 1) * 512KByte = %0.3fGB", (double)(SD_GetField(CSD, sizeof(CSD), 22, 48) + 1) * 512 * 1024 / 1024 / 1024 / 1024);
- break;
- case 2:
- printf("\r\nCSD Version 3.0 : Ultra Capacity(SDUC)");
- break;
- case 3:
- printf("\r\nReserved");
- break;
- default:
- break;
- }
- }
运行结果：
SPI模式下SD支持的命令有很多，但并不是都需要实现的，为了减少不必要的代码，我们仅实现有需要的部分，比如初始化部分的CMD0、CMD8、CMD55、CMD58、ACMD41等，在后面对SD卡读写操作的CMD17、CMD24等，而对于获取SD卡的CID、CSD信息的命令，则是可以省略不需要实现的。
6.Petit FAT移植
Petit FAT移植都统一在diskio.c文件中实现，diskio.c文件中提供了3个接口函数，分别为disk_initialize、disk_readp、disk_writep；接下面我们对这3个函数进行说明和移植。
6.1.disk_initialize
这个函数是初始化SD卡存储设备的，就是SD卡的初始化流程，我们可以把SD_Init函数放到此处调用，这个函数是在调用pf_mount挂载设备时，进行初始化调用的。具体实现如下所示：
- /**
- * [url=home.php?mod=space&uid=247401]@brief[/url] Initialize Disk Drive
- */
- DSTATUS disk_initialize(void)
- {
- DSTATUS stat;
- // Put your code here
- stat = SD_Init();
- return (stat);
- }
6.2.disk_readp
这个函数是读取扇区数据的，它有4个参数，分别为buff、sector、offset、count，其中buff存放读取到的数据，如果buff是空指针，那后面的读取的数据只做空读操作，读到的数据不会存储到内存空间；sector表示扇区的地址，这边需要注意一下，sector不需要再去乘以BLOCKLEN了！这边是在调试的时候趟过的坑^^，offset是扇区中要开始读取数据的偏移位置，count表示要读取的字节数；这边的(offset + count)不得超过扇区大小，即512。
在实现这个函数时，通过调用SPI模式下的CMD17命令，CMD17是读取一个完整扇区的数据，我们在移植的时候空读/省略存储offset之前读取到的数据，从offset开始存储count字节数据，然后对不满一个扇区的数据再做空读/省略存储操作，需要注意的是，每个扇区读取之后还有一个CRC16的校验码需要读取，具体的移植代码如下所示：
- /**
- * [url=home.php?mod=space&uid=247401]@brief[/url] Read Partial Sector
- * @param buff : Pointer to the destination object
- * @param sector : Sector number (LBA)
- * @param offset : Offset in the sector
- * @param count : Byte count (bit15:destination)
- */
- DRESULT disk_readp(BYTE *buff, DWORD sector, UINT offset, UINT count)
- {
- DRESULT res;
- // Put your code here
- res = RES_ERROR;
- if (SD_SendCommand(CMD17, sector) == 0)
- {
- while (SD_SPI_ReadWriteByte(0xFF) != 0xFE)
- {
- __ASM("nop");
- }
- for (UINT i = 0; i < offset; i++)
- {
- SD_SPI_ReadWriteByte(0xFF);
- }
- if (buff)
- {
- for (UINT i = 0; i < count; i++)
- {
- buff[i] = SD_SPI_ReadWriteByte(0xFF);
- }
- }
- else
- {
- for (UINT i = 0; i < count; i++)
- {
- SD_SPI_ReadWriteByte(0xFF);
- }
- }
- for (UINT i = 0; i < (512 + 2 - offset - count); i++)
- {
- SD_SPI_ReadWriteByte(0xFF);
- }
- res = RES_OK;
- }
- #if 0
- printf("\r\n%s sector = %d, offset = %d, count = %d", __FUNCTION__, sector, offset, count);
- printf("\r\n Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F");
- for (UINT i = 0; i < offset % 16; i++)
- {
- if ((i % 16) == 0)
- {
- printf("\r\n%09X ", sector * 512 + ((offset + 0) / 16) * 16);
- }
- printf(" ");
- }
- for (UINT i = 0; i < count; i++)
- {
- if (((offset + i) % 16) == 0)
- {
- printf("\r\n%09X ", sector * 512 + ((offset + i) / 16) * 16);
- }
- printf("%02X ", buff[i]);
- }
- printf("\r\n");
- #endif
- return (res);
- }
6.3.disk_writep
这个函数是把数据写入到扇区，这个函数仅有两个参数，分别为buff和sc；这个需要应用搭配来使用：当buff为空指针时，如果sc为0表示数据包写完了，此时进行结束处理操作流程；如果sc不为0表示即将开始写入数据操作，此时sc表示扇区地址，就做好准备。当buff不为空指针时，此时进行数据写入操作，sc表示当前要写入的数据个数。
在实现这个函数时，通过调用SPI模式下的CMD24命令，CMD24是写入一个完整扇区数据；所以当写入扇区的数据量不满1个扇区字节时，是需要补充写完整的；具体的移植代码如下所示：
- /**
- * [url=home.php?mod=space&uid=247401]@brief[/url] Write Partial Sector
- * @param buff : Pointer to the data to be written, NULL:Initiate/Finalize write operation
- * @param sc : Sector number (LBA) or Number of bytes to send
- */
- DRESULT disk_writep(const BYTE *buff, DWORD sc)
- {
- DRESULT res;
- static DWORD bw = 0;
- res = RES_ERROR;
- if (!buff)
- {
- if (sc)
- {
- // Initiate write process
- if (SD_SendCommand(CMD24, sc) == 0)
- {
- SD_SPI_ReadWriteByte(0xFF);
- SD_SPI_ReadWriteByte(0xFE);
- bw = 512 + 2; /* BLOCKLEN + CRC16 */
- res = RES_OK;
- #if 0
- printf("\r\n%s Initiate, sc = %5d, bw = %d", __FUNCTION__, sc, bw);
- #endif
- }
- }
- else
- {
- // Finalize write process
- for (DWORD i = 0; i < bw; i++)
- {
- SD_SPI_ReadWriteByte(0x00);
- }
- /* Wait Data accepted */
- while ((SD_SPI_ReadWriteByte(0xFF) & 0x1F) != 0x05)
- {
- __ASM("nop");
- }
- while (SD_SPI_ReadWriteByte(0xFF) == 0x00)
- {
- __ASM("nop");
- }
- res = RES_OK;
- #if 0
- printf("\r\n%s Finalize, sc = %d, bw = %d", __FUNCTION__, sc, bw);
- #endif
- }
- }
- else
- {
- // Send data to the disk
- for (DWORD i = 0; i < sc; i++)
- {
- SD_SPI_ReadWriteByte(buff[i]);
- }
- bw = bw - sc;
- res = RES_OK;
- #if 0
- printf("\r\n%s SendData, sc = %d, bw = %d", __FUNCTION__, sc, bw);
- #endif
- }
- return (res);
- }
7.Petit FAT配置
在pffconf.h文件中，是关于Petit FAT的配置，其中有功能函数的使能开关、FAT支持的格式选择、以及PF_USE_LCC这个宏的配置；下表显示了通过配置选项删除了哪些功能以减少代码空间：
着重说一下PF_USE_LCC这个宏，这边是在调试的时候趟过的坑^^，其默认值为0；当SD卡中的文件名为“HELLO.txt”时，我在使用pf_open函数打开这个文件，会提示：FR_NO_FILE，原因是因为在SD卡的根目录中，所有的文件名和文件后缀名都是大写的，当使用"HELLO.txt"和“HELLO.TXT”进行文本比较时，肯定不会匹配通过，所以解决的办法有两个：一是将PF_USE_LCC的宏值修改为1，二是在pf_open打开文件时，将文件名和文件后缀名都改为大写。
8.Petit FAT示例
在完成移植和配置后，我们就可以对TF卡中的文件进行读写了，编写了一个读写文件的示例函数，如下所示：
- FATFS fs; /* Work area (file system object) for the volume */
- void Petit_FatFs_Sample(void)
- {
- BYTE buff[16]; /* File read/write buffer */
- UINT br = 0; /* File read count */
- UINT bw = 0; /* File write count */
- FRESULT res; /* Petit FatFs function common result code */
- printf("\r\n");
- printf("\r\n%s", __FUNCTION__);
- printf("\r\n");
- res = pf_mount(&fs);
- if (res == FR_OK)
- {
- printf("\r\npf_mount successed");
- printf("\r\n------------------------------pf_write------------------------------");
- res = pf_open("HELLO.TXT");
- if (res == FR_OK)
- {
- printf("\r\npf_open successed");
-
- memset(buff, 0, sizeof(buff));
- memcpy(buff, "Hello", 5);
- res = pf_lseek(fs.fptr + 0);
- printf("\r\npf_lseek : %d, ofs = %d", res, 0);
- res = pf_write(buff, strlen((char *)buff), &bw);
- printf("\r\npf_write : %d, bw = %d,", res, bw);
- /* Finalize the current write operation */
- res = pf_write(0, 0, &bw);
- printf("\r\npf_write : %d, bw = %d,", res, bw);
- memset(buff, 0, sizeof(buff));
- memcpy(buff, "World", 5);
- res = pf_lseek(fs.fptr + 512);
- printf("\r\npf_lseek : %d, ofs = %d", res, 512);
- res = pf_write(buff, strlen((char *)buff), &bw);
- printf("\r\npf_write : %d, bw = %d,", res, bw);
- /* Finalize the current write operation */
- res = pf_write(0, 0, &bw);
- printf("\r\npf_write : %d, bw = %d,", res, bw);
- }
- else
- {
- printf("\r\npf_open : %d", res);
- }
- printf("\r\n------------------------------pf_read------------------------------");
- res = pf_open("HELLO.TXT");
- if (res == FR_OK)
- {
- printf("\r\npf_open successed");
- do
- {
- res = pf_read(buff, sizeof(buff), &br);
- if ((res == FR_OK) && (br != 0))
- {
- printf("\r\npf_read : %s, br = %d", buff, br);
- }
- else
- {
- printf("\r\npf_read : %d", res);
- }
- } while (br != 0);
- }
- else
- {
- printf("\r\npf_open : %d", res);
- }
- }
- else
- {
- printf("\r\npf_mount : %d", res);
- }
- }
在函数中，先挂载了FAT文件系统，监控打印如下所示：
然后通过pf_open来打开文件，pf_open通过读取根目录扇区的数据进行比较判断，监控打印如下所示：
在文件打开成功后，我们就可以通过pf_write和pf_read来读写文件中的数据了。
9.注意事项
9.1.Petit FAT在使用时还是有一些限制的，它无法创建文件，只能打开现有已经存在的文件、无法追加数据和扩展文件大小、文件的时间戳不会更新、只读属性的文件也无法阻止写入操作
9.2.pf_lseek函数的使用，要在pf_open成功之后，其参数ofs需要是扇区的倍数值，才有效；
9.3.pf_write函数写入操作只能在扇区边上启动和停止，就是说一次写一个扇区（512字节），如果不满一个扇区数据，会通根据移植的disk_writep的功能填入0；另外就是一旦启动写操作，就必须正确完成，期间不允许有其它操作函数，否则写入的数据可能会丢失；
9.4.文件写操作顺序：- pf_lseek(ofs) 在启动定稿操作之前，必须将读/写指针移动到扇区边界，否则它将在第一次定稿操作时向下舍入到扇区边界
- pf_write(buff, btw, &bw) 启动写入操作，将第一批数据写入文件
- pf_write(buff, btw, &bw) 写入下一批数据，在进行写入操作时，不能使用任何其它文件函数
- pf_write(0, 0, &bw) 完成当前写入操作，如果读/写指针不在扇区边界上，则扇区中的其余字节将被填充为零
10.程序空间编译比较
没有添加Petit FAT时：
添加Petit FAT示例后：
11.附件
《Physical Layer Simplified Specification Version 9.10》手册：
Part1 Physical Layer Simplified Specification Version 9.10 December 1, 2023.PDF
(5.85 MB, 下载次数: 56)
SD_Information信息读取示例程序：
LibSamples_MM32G0001_V2.0.2_SD_Information.zip
(6.12 MB, 下载次数: 49)
Petit FAT读写示例程序：
LibSamples_MM32G0001_V2.0.2_Petit_FatFs.zip
(6.17 MB, 下载次数: 57)
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