单片机读写sd卡例程与电路原理图

51单片机读写sd卡例程分享给大家

电路原理图如下：


单片机源程序如下:

1. /**************************************************************************************
   
2. //------------------ MMC/SD-Card Reading and Writing implementation -------------------
   
3. ****************************************************************************************/
   
4. sbit SPI_DI =P2^1;
   
5. sbit SPI_DO =P2^5;
   
6. sbit SPI_SCL=P2^2;
   
7. sbit SPI_CS =P2^0;
   
8. 
   
9. 
   
10. //------------------------------------------------------------
    
11. // Error define
    
12. //-------------------------------------------------------------
    
13. #define INIT_CMD0_ERROR     0x01
    
14. #define INIT_CMD1_ERROR                0x02
    
15. #define WRITE_BLOCK_ERROR        0x03
    
16. #define READ_BLOCK_ERROR           0x04
    
17. //-------------------------------------------------------------
    
18. 
    
19. // data type
    
20. //-------------------------------------------------------------   
    
21. // this structure holds info on the MMC card currently inserted
    
22. 
    
23. typedef struct MMC_VOLUME_INFO
    
24. { //MMC/SD Card info
    
25.   unsigned int  size_MB;
    
26.   unsigned char sector_multiply;
    
27.   unsigned int  sector_count;
    
28.   unsigned char name[6];
    
29. } VOLUME_INFO_TYPE;
    
30. 
    
31. typedef struct STORE
    
32. {
    
33.   unsigned char dat[100];
    
34. } BUFFER_TYPE; //256 bytes, 128 words
    
35. 
    
36. BUFFER_TYPE sectorBuffer; //512 bytes for sector buffer
    
37. 
    
38. //--------------------------------------------------------------
    
39. unsigned int  readPos=0;
    
40. unsigned char sectorPos=0;
    
41. unsigned char LBA_Opened=0; //Set to 1 when a sector is opened.
    
42. unsigned char Init_Flag;    //Set it to 1 when Init is processing.
    
43. //---------------------------------------------------------------
    
44. 
    
45. void delay(unsigned int time)
    
46. {
    
47. while(time--);
    
48. }
    
49. 
    
50. //****************************************************************************
    
51. // Port Init
    
52. void MMC_Port_Init()
    
53. //****************************************************************************
    
54. {
    
55.    SPI_SCL=1;
    
56.    SPI_DO =1;
    
57.    SPI_CS=1;
    
58.    send_s("Port Init!");
    
59. /*
    
60.    //Config ports
    
61.    SPI_DI=1;          //Set Pin MMC_DI as Input
    
62.    SPI_SCL=1;         //Set Pin MMC_Clock as Output
    
63.    SPI_DO=1;          //Set Pin MMC_DO as Output
    
64.    SPI_CS=1;          //Set MMC_Chip_Select to High,MMC/SD Invalid.
    
65.    //busy led port init
    
66.    //SPI_BY=1;        //Set spi busy led port output
    
67.    //MMC_BUSY_LED=1;                      //busy led off     
    
68.    */               
    
69. }
    
70. 
    
71. //****************************************************************************
    
72. //Routine for sending a byte to MMC/SD-Card
    
73. void Write_Byte_MMC(unsigned char value)
    
74. //****************************************************************************
    
75. {
    
76.    unsigned char i;
    
77.    
    
78.    //Software SPI
    
79.    for (i=0;i<8;i++)
    
80.    {  //write a byte
    
81.       if (((value>>(7-i))&0x01)==0x01)
    
82.            SPI_DI=1; //Send bit by bit(MSB First)
    
83.       else SPI_DI=0;
    
84.        SPI_SCL=0; //set Clock Impuls low
    
85.       if(Init_Flag)
    
86.            delay(9);
    
87.       SPI_SCL=1; //set Clock Impuls High
    
88.       if(Init_Flag)
    
89.            delay(9);     
    
90.    }//write a byte
    
91.    //MMC_BUSY_LED=1;
    
92. }
    
93. 
    
94. //****************************************************************************
    
95. //Routine for reading a byte from MMC/SD-Card
    
96. unsigned char Read_Byte_MMC()
    
97. //****************************************************************************
    
98. {
    
99.    unsigned char temp=0;
    
100.    unsigned char i;
     
101. 
     
102.    //Software SPI
     
103.    for (i=0;i<8;i++) //MSB First
     
104.    {
     
105.       SPI_DO=1;
     
106.       SPI_SCL=0; //Clock Impuls (Low)
     
107.       if(Init_Flag)
     
108.            delay(9);
     
109.       temp=(temp<<1)+(unsigned char)SPI_DO; //read mmc data out pin
     
110.       SPI_SCL=1; //set Clock Impuls High
     
111.       if(Init_Flag)
     
112.            delay(9);       
     
113.    }
     
114.    return (temp);
     
115. }
     
116. 
     
117. //****************************************************************************
     
118. //Send a Command to MMC/SD-Card
     
119. //Return: the second byte of response register of MMC/SD-Card
     
120. unsigned char Write_Command_MMC(unsigned char *CMD)
     
121. //****************************************************************************
     
122. {
     
123.    unsigned char tmp;
     
124.    unsigned char retry=0;
     
125.    unsigned char i;
     
126. 
     
127.    //set MMC_Chip_Select to high (MMC/SD-Card disable)
     
128.    SPI_CS=1;
     
129.    //send 8 Clock Impulse
     
130.    Write_Byte_MMC(0xFF);
     
131.    //set MMC_Chip_Select to low (MMC/SD-Card active)
     
132.    SPI_CS=0;
     
133. 
     
134.    //send 6 Byte Command to MMC/SD-Card
     
135.    for (i=0;i<0x06;i++)
     
136.    {
     
137.       Write_Byte_MMC(*CMD++);
     
138.    }
     
139.    
     
140.    //get 16 bit response
     
141.    Read_Byte_MMC(); //read the first byte,ignore it.
     
142.    do
     
143.    {  //Only last 8 bit is used here.Read it out.
     
144.       tmp = Read_Byte_MMC();
     
145.       retry++;
     
146.    }
     
147.    while((tmp==0xff)&&(retry<100));
     
148.    return(tmp);
     
149. }
     
150. 
     
151. //****************************************************************************
     
152. //Routine for Init MMC/SD card(SPI-MODE)
     
153. unsigned char MMC_Init()
     
154. //****************************************************************************
     
155. {  
     
156.    unsigned char retry,temp;
     
157.    unsigned char i;
     
158.    unsigned char CMD[] = {0x40,0x00,0x00,0x00,0x00,0x95};
     
159.    send_s("SD CARD Init!");
     
160.    MMC_Port_Init(); //Init SPI port  
     
161. 
     
162.    delay(200);
     
163.    
     
164.    Init_Flag=1; //Set the init flag
     
165. 
     
166.    for (i=0;i<0x0f;i++)
     
167.    {
     
168.       Write_Byte_MMC(0xff); //send 74 clock at least!!!
     
169.    }
     
170.        
     
171.    //Send Command CMD0 to MMC/SD Card
     
172.    send_s("Send Command CMD0 to MMC/SD Card");
     
173.    retry=0;
     
174.    do
     
175.    { //retry 200 times to send CMD0 command
     
176.      temp=Write_Command_MMC(CMD);
     
177.      retry++;
     
178.      if(retry==200)
     
179.      { //time out
     
180.        return(INIT_CMD0_ERROR);//CMD0 Error!
     
181.      }
     
182.    }
     
183.    while(temp!=1);
     
184.    
     
185.    //Send Command CMD1 to MMC/SD-Card
     
186.    send_s("Send Command CMD1 to MMC/SD-Card");
     
187.    CMD[0] = 0x41; //Command 1
     
188.    CMD[5] = 0xFF;
     
189.    retry=0;
     
190.    do
     
191.    { //retry 100 times to send CMD1 command
     
192.      temp=Write_Command_MMC(CMD);
     
193.      retry++;
     
194.      if(retry==100)
     
195.      { //time out
     
196.        return(INIT_CMD1_ERROR);//CMD1 Error!
     
197.      }
     
198.    }
     
199.    while(temp!=0);
     
200.    
     
201.    Init_Flag=0; //Init is completed,clear the flag
     
202.    
     
203.    SPI_CS=1;  //set MMC_Chip_Select to high
     
204.    send_s("SD CARD Init Suc!!");
     
205.    return(0x55); //All commands have been taken.
     
206. }
     
207. 
     
208. //****************************************************************************
     
209. //Routine for reading data Registers of MMC/SD-Card
     
210. //Return 0 if no Error.
     
211. unsigned char MMC_Read_Block(unsigned char *CMD,unsigned char *Buffer,unsigned int Bytes)
     
212. //****************************************************************************
     
213. {  
     
214.    unsigned int i;
     
215.    unsigned retry,temp;
     
216.    
     
217.    //Send Command CMD to MMC/SD-Card
     
218.    retry=0;
     
219.    do
     
220.    {  //Retry 100 times to send command.
     
221.       temp=Write_Command_MMC(CMD);
     
222.       retry++;
     
223.       if(retry==100)
     
224.       {
     
225.         return(READ_BLOCK_ERROR); //block write Error!
     
226.       }
     
227.    }
     
228.    while(temp!=0);
     
229.                           
     
230.    //Read Start Byte form MMC/SD-Card (FEh/Start Byte)
     
231.    while (Read_Byte_MMC()!=0xfe);
     
232.        
     
233.    //Write blocks(normal 512Bytes) to MMC/SD-Card
     
234.    for (i=0;i<Bytes;i++)
     
235.    {
     
236.       *Buffer++ = Read_Byte_MMC();
     
237.    }
     
238.    
     
239.    //CRC-Byte
     
240.    Read_Byte_MMC();//CRC - Byte
     
241.    Read_Byte_MMC();//CRC - Byte
     
242.        
     
243.    //set MMC_Chip_Select to high (MMC/SD-Card invalid)
     
244.    SPI_CS=1;
     
245.    return(0);
     
246. }
     
247. 
     
248. //***************************************************************************
     
249. //Routine for reading CSD Registers from MMC/SD-Card (16Bytes)
     
250. //Return 0 if no Error.
     
251. unsigned char Read_CSD_MMC(unsigned char *Buffer)
     
252. //***************************************************************************
     
253. {       
     
254.    //Command for reading CSD Registers
     
255.    unsigned char CMD[] = {0x49,0x00,0x00,0x00,0x00,0xFF};
     
256.    unsigned char temp;
     
257.    temp=MMC_Read_Block(CMD,Buffer,16); //read 16 bytes
     
258. 
     
259.    return(temp);
     
260. }
     
261. 
     
262. //***************************************************************************
     
263. //Routine for reading CID Registers from MMC/SD-Card (16Bytes)
     
264. //Return 0 if no Error.
     
265. unsigned char Read_CID_MMC(unsigned char *Buffer)
     
266. //***************************************************************************
     
267. {
     
268.    //Command for reading CID Registers
     
269.    unsigned char CMD[] = {0x4A,0x00,0x00,0x00,0x00,0xFF};
     
270.    unsigned char temp;
     
271.    temp=MMC_Read_Block(CMD,Buffer,16); //read 16 bytes
     
272. 
     
273.    return(temp);
     
274. }
     
275. 
     
276. //****************************************************************************
     
277. //returns the :
     
278. //         size of the card in MB ( ret * 1024^2) == bytes
     
279. //         sector count and multiplier MB are in u08 == C_SIZE / (2^(9-C_SIZE_MULT))
     
280. //         name of the media
     
281. void MMC_get_volume_info(void)
     
282. //****************************************************************************
     
283. {   unsigned char i;
     
284.     unsigned char c_temp[5];
     
285.     VOLUME_INFO_TYPE MMC_volume_Info,*vinf;
     
286.     send_s("SD CARD Information Read!!");
     
287.     vinf=&MMC_volume_Info; //Init the pointoer;
     
288.         // read the CSD register
     
289.     Read_CSD_MMC(sectorBuffer.dat);
     
290.         // get the C_SIZE value. bits [73:62] of data
     
291.         // [73:72] == sectorBuffer.data[6] && 0x03
     
292.         // [71:64] == sectorBuffer.data[7]
     
293.         // [63:62] == sectorBuffer.data[8] && 0xc0
     
294.         vinf->sector_count = sectorBuffer.dat[6] & 0x03;
     
295.         vinf->sector_count <<= 8;
     
296.         vinf->sector_count += sectorBuffer.dat[7];
     
297.         vinf->sector_count <<= 2;
     
298.         vinf->sector_count += (sectorBuffer.dat[8] & 0xc0) >> 6;
     
299.                
     
300.         // get the val for C_SIZE_MULT. bits [49:47] of sectorBuffer.data
     
301.         // [49:48] == sectorBuffer.data[5] && 0x03
     
302.         // [47]    == sectorBuffer.data[4] && 0x80
     
303.         vinf->sector_multiply = sectorBuffer.dat[9] & 0x03;
     
304.         vinf->sector_multiply <<= 1;
     
305.         vinf->sector_multiply += (sectorBuffer.dat[10] & 0x80) >> 7;
     
306. 
     
307.         // work out the MBs
     
308.         // mega bytes in u08 == C_SIZE / (2^(9-C_SIZE_MULT))
     
309.         vinf->size_MB = vinf->sector_count >> (9-vinf->sector_multiply);
     
310.         // get the name of the card
     
311.         Read_CID_MMC(sectorBuffer.dat);
     
312.         vinf->name[0] = sectorBuffer.dat[3];
     
313.         vinf->name[1] = sectorBuffer.dat[4];
     
314.         vinf->name[2] = sectorBuffer.dat[5];
     
315.         vinf->name[3] = sectorBuffer.dat[6];
     
316.         vinf->name[4] = sectorBuffer.dat[7];
     
317.         vinf->name[5] = 0x00; //end flag
     
318.         //----------------------------------------------------------
     
319.         /*
     
320.         while(1)
     
321.         {
     
322.          P1=~(unsigned char)((vinf->size_MB)>>8);
     
323.          delay(50000);
     
324.          delay(50000);
     
325.          delay(50000);
     
326.          delay(50000);
     
327.          delay(50000);
     
328.          P1=~(unsigned char)((vinf->size_MB));
     
329.          delay(50000);
     
330.          delay(50000);
     
331.          delay(50000);
     
332.          delay(50000);
     
333.          delay(50000);
     
334.         }*/
     
335.     //LCDclrscr();
     
336.     //Print Product name on lcd
     
337.     i=0;
     
338.     send_s("Product Name:");
     
339.     //while((vinf->name[i]!=0x00)&&(i<16)) send(vinf->name[i++]);
     
340.         send_s(vinf->name);
     
341.     //Print Card Size(eg:128MB)
     
342.     //gotoxy(1,0);
     
343.     send_s("Tot:");
     
344.     send_s(ftoa(vinf->size_MB,c_temp,0));
     
345.         send_s("MB ");
     
346.     //gotoxy(2,0);
     
347.     //writestring("sector_mult:"); writeNumber(vinf->sector_multiply);
     
348.     //gotoxy(3,0);
     
349.    
     
350. ……………………
     
351. 
     
352. …………限于本文篇幅 余下代码请从51黑下载附件…………
     

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不知道为什么,到了Send Command CMD0 to MMC/SD Card  后,就没见发送CMD1命令?