sd卡读写——sd example阅读

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 32 /*****************************************************************************/
 33 /**
 34 *这里的注释很重要，不能忽略
 35 * @file xilffs_polled_example.c
 36 *
 37 *
 38 * @note This example uses file system with SD to write to and read from
 39 * an SD card using ADMA2 in polled mode.轮询读写adma2
 40 * To test this example File System should not be in Read Only mode测试要求：文件系统不能只读
 41 * To test this example USE_MKFS option should be true.zynq上需要选ues_mkfs
 42 *

 43 * This example was tested using SD2.0 card and eMMC (using eMMC to SD adaptor).
 44 *
 45 * To test with different logical drives, drive number should be mentioned in
 46 * both FileName and Path variables. By default, it will take drive 0 if drive
 47 * number is not mentioned in the FileName variable.板子选项里sd口有两个，需要选和对应
 48 * For example, to test logical drive 1
 49 * FileName =  "1:/<file_name>" and Path = "1:/"
 50 * Similarly to test logical drive N, FileName = "N:/<file_name>" and
 51 * Path = "N:/"
 52 *
 53 * None.
 54 *
 55 * <pre>
 56 * MODIFICATION HISTORY:
 57 *
 58 * Ver   Who Date     Changes
 59 * ----- --- -------- -----------------------------------------------
 60 * 1.00a hk  10/17/13 First release
 61 * 2.2   hk  07/28/14 Make changes to enable use of data cache.
 62 * 2.5   sk  07/15/15 Used File size as 8KB to test on emulation platform.
 63 * 2.9   sk  06/09/16 Added support for mkfs.
 64 *
 65 *</pre>
 66 *
 67 ******************************************************************************/
 68 
 69 /***************************** Include Files *********************************/
 70 
 71 #include "xparameters.h"    /* SDK generated parameters */
 72 #include "xsdps.h"        /* SD device driver */
 73 #include "xil_printf.h"
 74 #include "ff.h"
 75 #include "xil_cache.h"
 76 #include "xplatform_info.h"
 77 
 78 /************************** Constant Definitions *****************************/
 79 
 80 
 81 /**************************** Type Definitions *******************************/
 82 
 83 /***************** Macros (Inline Functions) Definitions *********************/
 84 
 85 /************************** Function Prototypes ******************************/
 86 int FfsSdPolledExample(void);
 87 
 88 /************************** Variable Definitions *****************************/
 89 static FIL fil;        /* File object */
 90 static FATFS fatfs;
 91 /*
 92  * To test logical drive 0, FileName should be "0:/<File name>" or
 93  * "<file_name>". For logical drive 1, FileName should be "1:/<file_name>"
 94  */
 95 static char FileName[32] = "Test.bin";//文件名
 96 static char *SD_File;//申请指针
 97 u32 Platform;//后面用来存平台的信息
 98 
 99 #ifdef __ICCARM__
100 #pragma data_alignment = 32 //数据位数，后面根据平台信息变大小
101 u8 DestinationAddress[10*1024*1024];//读出数据
102 u8 SourceAddress[10*1024*1024];//源数据
103 #pragma data_alignment = 4 
104 #else
105 u8 DestinationAddress[10*1024*1024] __attribute__ ((aligned(32)));
106 u8 SourceAddress[10*1024*1024] __attribute__ ((aligned(32)));
107 #endif
108 
109 #define TEST 7
110 
111 /*****************************************************************************/
112 /**
113 *调用方法，想起了OO
114 * Main function to call the SD example.
115 *
116 * @param    None
117 *
118 * @return    XST_SUCCESS if successful, otherwise XST_FAILURE.
119 *
120 * @note        None
121 *
122 ******************************************************************************/
123 int main(void)
124 {
125     int Status;
126 
127     xil_printf("SD Polled File System Example Test \r\n");//这个是板子打出来的，要接串口
128 
129     Status = FfsSdPolledExample();
130     if (Status != XST_SUCCESS) {
131         xil_printf("SD Polled File System Example Test failed \r\n");
132         return XST_FAILURE;
133     }
134 
135     xil_printf("Successfully ran SD Polled File System Example Test \r\n");
136 
137     return XST_SUCCESS;
138 
139 }
140 
141 /*****************************************************************************/
142 /**
143 *
144 * File system example using SD driver to write to and read from an SD card
145 * in polled mode. This example creates a new file on an
146 * SD card (which is previously formatted with FATFS), write data to the file
147 * and reads the same data back to verify.
148 *写完读出并检查
149 * @param    None
150 *
151 * @return    XST_SUCCESS if successful, otherwise XST_FAILURE.
152 *
153 * @note        None
154 *
155 ******************************************************************************/
156 int FfsSdPolledExample(void)
157 {
158     FRESULT Res;//
159     UINT NumBytesRead;
160     UINT NumBytesWritten;
161     u32 BuffCnt;
162     u32 FileSize = (8*1024*1024);
163     /*
164      * To test logical drive 0, Path should be "0:/"
165      * For logical drive 1, Path should be "1:/"
166      */
167     TCHAR *Path = "0:/";
168 
169     Platform = XGetPlatform_Info();//获得平台信息
170     if (Platform == XPLAT_ZYNQ_ULTRA_MP) {//如果是ultra
171         /*
172          * Since 8MB in Emulation Platform taking long time, reduced
173          * file size to 8KB.减大小
174          */
175         FileSize = 8*1024;
176     }
177 
178     for(BuffCnt = 0; BuffCnt < FileSize; BuffCnt++){
179         SourceAddress[BuffCnt] = TEST + BuffCnt;//给地址赋值，test应该是基地址？前面宏定义为7
180     }
181 
182     /*
183      * Register volume work area, initialize device
184      */
185     Res = f_mount(&fatfs, Path, 0);//初始化？文件系统指针（前面的静态变量），通道，模式
　　　　　　　　　　　　　　　　　　　　　　　　//fatfs在哪里赋的值？
　　　　　　　　　　　　　　　　　　　　　　　　//https://blog.csdn.net/lbaihao/article/details/75144011
186 
187     if (Res != FR_OK) { //失败
188         return XST_FAILURE;
189     }
190 
191     /*
192      * Path - Path to logical driver, 0 - FDISK format.
193      * 0 - Cluster size is automatically determined based on Vol size.
194      */
195     Res = f_mkfs(Path, 0, 0);//建立fat系统
196     if (Res != FR_OK) {
197         return XST_FAILURE;
198     }
199 
200     /*
201      * Open file with required permissions.
202      * Here - Creating new file with read/write permissions. .
203      * To open file with write permissions, file system should not
204      * be in Read Only mode.
205      */
206     SD_File = (char *)FileName;//FileName是之前的常量"Test.bin"
207 
208     Res = f_open(&fil, SD_File, FA_CREATE_ALWAYS | FA_WRITE | FA_READ);//新建读写文件并打开，给指针fil
209     if (Res) {
210         return XST_FAILURE;
211     }
212 
213     /*
214      * Pointer to beginning of file .
215      */
216     Res = f_lseek(&fil, 0);//移到文件开始位
217     if (Res) {
218         return XST_FAILURE;
219     }
220 
221     /*
222      * Write data to file.写数据
223      */
224     Res = f_write(&fil, (const void*)SourceAddress, FileSize,
225             &NumBytesWritten);//源数据要是const，第二个参数是buf，写的内容
226     if (Res) {
227         return XST_FAILURE;
228     }
229 
230     /*
231      * Pointer to beginning of file .
232      */
233     Res = f_lseek(&fil, 0);
234     if (Res) {
235         return XST_FAILURE;
236     }
237 
238     /*
239      * Read data from file.读数据
240      */
241     Res = f_read(&fil, (void*)DestinationAddress, FileSize,
242             &NumBytesRead);
243     if (Res) {
244         return XST_FAILURE;
245     }
246 
247     /*
248      * Data verification 比较读写内容是否一致
249      */
250     for(BuffCnt = 0; BuffCnt < FileSize; BuffCnt++){
251         if(SourceAddress[BuffCnt] != DestinationAddress[BuffCnt]){
252             return XST_FAILURE;
253         }
254     }
255 
256     /*
257      * Close file.关文件
258      */
259     Res = f_close(&fil);
260     if (Res) {
261         return XST_FAILURE;
262     }
263 
264     return XST_SUCCESS;
265 }