sd_mmc.c

一个SD卡读写源码. KEIL环境下. 做嵌入式开发驱动的值得一看!

#include "stm32f10x_lib.h"
#include"hardware.h"
#include "SD_MMC.h"

void SPI_Config(void)	 ;
#define	SPI_CS_Assert()     GPIO_ResetBits(GPIOD, GPIO_Pin_9)
/* Deselect MSD Card: ChipSelect pin high */
#define SPI_CS_Deassert()    GPIO_SetBits(GPIOD, GPIO_Pin_9)

unsigned char SPI_WriteByte(unsigned char data)
{
 uint8 Data = 0;

  /* Wait until the transmit buffer is empty */
  while (SPI_GetFlagStatus(SPI1, SPI_FLAG_TXE) == RESET);
  /* Send the byte */
  SPI_SendData(SPI1, data);

  /* Wait until a data is received */
  while (SPI_GetFlagStatus(SPI1, SPI_FLAG_RXNE) == RESET);
  /* Get the received data */
  Data = SPI_ReceiveData(SPI1);

  /* Return the shifted data */
  return Data;
}

//sd卡写命令		//sd send command
uint8 MMC_SD_SendCommand(uint8 cmd, uint32 arg)
{
	uint8 r1;
	uint8 retry=0;
	
	SPI_WriteByte(0xff);
	SPI_CS_Assert();
	
	SPI_WriteByte(cmd | 0x40);//分别写入命令	//send command
	SPI_WriteByte(arg>>24);
	SPI_WriteByte(arg>>16);
	SPI_WriteByte(arg>>8);
	SPI_WriteByte(arg);
	SPI_WriteByte(0x95);
	
	while((r1 = SPI_WriteByte(0xff)) == 0xff)//等待响应，	//wait response
		if(retry++ > 200) break;//超时退出					//time out error

	SPI_CS_Deassert();

	return r1;//返回状态值					//return state
}

//sd卡复位		//reset sd card (software)
uint8 MMC_SD_Reset(void)
{
	uint8 i;
	uint8 retry;
	uint8 r1=0;
	retry = 0;

	SPI_Config();
    GPIO_ResetBits(GPIOD, GPIO_Pin_10);
    delay(1000);
  /* MSD chip select high */
    SPI_CS_Deassert();
	do
	{
		for(i=0;i<10;i++) SPI_WriteByte(0xff);
		r1 = MMC_SD_SendCommand(0, 0);//发idle命令	//send idle command
		retry++;
		if(retry>100) return 1;//超时退出		//time out
	} while(r1 != 0x01);	


	retry = 0;
	do
	{
		r1 = MMC_SD_SendCommand(1, 0);//发active命令	//send active command
		retry++;
		if(retry>200) return 1;//超时退出		//time out
	} while(r1);
	//SPI_High();
	r1 = MMC_SD_SendCommand(59, 0);//关crc		//disable CRC

	r1 = MMC_SD_SendCommand(16, 512);//设扇区大小512	//set sector size to 512
	return 0;//正常返回		//normal return
}

//读一个扇区		//read one sector
uint8 MMC_SD_ReadSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	//uint8 retry=0;

	r1 = MMC_SD_SendCommand(17, sector<<9);//读命令	//read command
	
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert();
	//等数据的开始	//wait to start recieve data
	while(SPI_WriteByte(0xff) != 0xfe);//if(retry++ > 50){SPI_CS_Deassert();return 1;}

	for(i=0; i<512; i++)//读512个数据	//read 512 bytes
	{
		*buffer++ = SPI_WriteByte(0xff);
	}

	SPI_WriteByte(0xff);//伪crc
	SPI_WriteByte(0xff);
	
	SPI_CS_Deassert();

	return 0;
}


//写一个扇区		//wirite one sector //not used in this application
uint8 MMC_SD_WriteSingleBlock(uint32 sector, uint8* buffer)
{
	uint8 r1;
	uint16 i;
	//uint8 retry=0;

	r1 = MMC_SD_SendCommand(24, sector<<9);//写命令	//send command
	if(r1 != 0x00)
		return r1;

	SPI_CS_Assert();
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);

	SPI_WriteByte(0xfe);//发开始符			//send start byte
	
	for(i=0; i<512; i++)//送512字节数据		//send 512 bytes data
	{
		SPI_WriteByte(*buffer++);
	}
	
	SPI_WriteByte(0xff);
	SPI_WriteByte(0xff);
	
	r1 = SPI_WriteByte(0xff);
	
	if( (r1&0x1f) != 0x05)//等待是否成功	//judge if it successful
	{
		SPI_CS_Deassert();
		return r1;
	}
	//等待操作完		//wait no busy
	while(!SPI_WriteByte(0xff));//if(retry++ > 50){SPI_CS_Deassert();return 1;}

	SPI_CS_Deassert();

	return 0;
}