單片機(jī)讀寫(xiě)SD卡教程

1、鄭重聲明：本實(shí)驗(yàn)并不是對(duì)所有SD卡都能成功運(yùn)行第一步：打開(kāi) win hex軟件，用讀卡器讀 SD卡，在win hex中查看SD卡FPrlrj舊nmg *御日曲日尺立件（日轄:號(hào)iifllPI譏吵：當(dāng)Tfllll春罰;I SW（£）旨口凹帶此|；也S X電a O C3* -0畫(huà)*電bld! IbiljUA 初1 悶1|館口曲佃AgraaSBJLXsta InAEiqptetEJ'03839535e on(«»： 0 16BH(*J-)： 0曲* ?；第詞EKt £i2f UrEiib&d MT 1 SOB66.5 K01.2 MBFamof

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14、quot;c d n發(fā)現(xiàn)DBR起始于0x11200扇區(qū)地址，它必是512整數(shù)倍，因?yàn)橐粋€(gè)扇區(qū)含 512BYTE，所以 在程序中讀一個(gè)扇區(qū)時(shí)一定要是 512整數(shù)倍，否則會(huì)出錯(cuò)。 11200地址對(duì)應(yīng)的值是0xEB， 本程序讀一下這個(gè)地址的值看看是否正確。注意有的win hex編址是十進(jìn)制看看程序吧#in elude <reg52.h>#defi ne uchar un sig ned char#defi ne uint un sig ned int/=/定義SD卡需要的4根信號(hào)線sbit SD_CLK = P1A1;sbit SD_DI = P1A2;sbit SD_DO = P1A0

15、；sbit SD_CS = PU3;sbit Beep=P2A0；用來(lái)調(diào)程序標(biāo)志 /=/=/定義512字節(jié)緩沖區(qū)，89C52直接定義成 unsigned char DATA80;，太大了 RAM不夠 un sig ned char xdata DATA512;void delay (un sig ned int z)un sig ned int x,y; for(x=z;x>0;x_);for(y=110;y>0;y-);/= /寫(xiě)一字節(jié)到 SD 卡,模擬 SPI 總線方式void SdWrite(unsigned char n)unsigned char i;for(i=8;i;

16、i-)SD_CLK=0;SD_DI=(n&0x80);n<<=1;SD_CLK=1;SD_DI=1;/= /從 SD 卡讀一字節(jié) ,模擬 SPI 總線方式unsigned char SdRead()unsigned char n,i;for(i=8;i;i-)SD_CLK=1;SD_CLK=0;n<<=1;if(SD_DO) n|=1;return n;/= /檢測(cè) SD 卡的響應(yīng)unsigned char SdResponse()uchar i=0,response=0;while(i<=8)response = SdRead(); if(respons

17、e=0x00)break;if(response=0x01)break;i+;return response; /= /發(fā)命令到 SD 卡void SdCommand(unsigned char command, unsigned long argument, unsigned char CRC) SdWrite(command|0x40);/*SdWrite(unsigned char *)&argument)0);SdWrite(unsigned char *)&argument)1);SdWrite(unsigned char *)&argument)2);SdW

18、rite(unsigned char *)&argument)3);*/SdWrite(argument>>24);SdWrite(argument>>16);SdWrite(argument>>8);SdWrite(argument);SdWrite(CRC);/= /初始化 SD 卡unsigned char SdInit(void)unsigned char i;unsigned char response=0xFF;P3=0xff;SD_CS=1;for(i=0;i<=0xfe;i+)SdWrite(0xff);SD_CS=0;SdCo

19、mmand(0x00,0,0x95);SD_DI=1; response=SdResponse();if(response!=0x01)return 0;if(response=0x01) / 不管什么 SD 卡都能進(jìn)入這一步，同時(shí)也說(shuō)明硬件沒(méi)問(wèn)題 SD_CS=1;/Beep=0;/while(1);/ 用來(lái)查看程序能否運(yùn)行到這一步，去掉/即可SdWrite(0xff);SD_CS=0;while(1)SdCommand(0x01,0,0xff);/SdCommand(0x01,0x00000000,0xff);/ 進(jìn) SPI response=0xff;SD_DI=1; for(i=0;i&

20、lt;250;i+)/response!=0x00/ 等待回復(fù) response=SdResponse(); /Beep=0;/ if(response=0) break;if(response=O) break;/回復(fù)0則通過(guò)SPI，只要通過(guò) SPI后面的指令才能繼/續(xù)/Beep=0;/Beep=0;看程序能否跳出來(lái)，挑不出來(lái)則進(jìn)不了SPISD_CS=1;SdWrite(0xff);SD_CS=0;/Beep=0;return 1;/=/往 SD 卡指定地址寫(xiě)數(shù)據(jù) ,一次最多 512 字節(jié) 最好不要亂寫(xiě) 否則 fat 系統(tǒng)被改掉 SD 卡打不 開(kāi)unsigned char SdWriteBl

21、ock(unsigned char *Block, unsigned long address,int len)unsigned int count;unsigned char dataResp;SD_CS=0;SdCommand(0x18,address,0xff);if(SdResponse()=00)SdWrite(0xff);SdWrite(0xff);SdWrite(0xff);/command was a success - now send data/start with DATA TOKEN = 0xFESdWrite(0xfe);/now send datafor(count

22、=0;count<len;count+) SdWrite(*Block+); for(;count<512;count+) SdWrite(0);/data block sent - now send checksumSdWrite(0xff); / 兩字節(jié) CRC 校驗(yàn) , 為 0XFFFF 表示不考慮 CRCSdWrite(0xff);/Now read in the DA TA RESPONSE token dataResp=SdRead();while(SdRead()=0); dataResp=dataResp&0x0f; /mask the high byte of the DATA RESPONSE token SD_CS=1;SdWrite(0xff); if(dataResp=0x0b) return 0;if(dataResp=0x05)return 1;return 0;/printf("Command 0x18 (Write) was not received by the SD.n"