I2C通讯的C语言程序

#include <INTRINS.H>
#include <stdio.h>
#include <reg51.h>

sbit SCK=0x91;//时钟线端口
sbit SDA=0x90;//数据线端口

#define  I2C_Address 0xa0 //I2C芯片地址
#define  nop _nop_()  
#define  NOP nop;nop;nop;nop;nop;nop//延时应大于4.7us

//开始信号
//在时钟线为高电平时,数据线由高向低跳变. 
void StartI2C(void)
{   SCK=1;
    SDA=1;
    NOP;
    SDA=0;
    NOP;
    SCK=0;
    NOP;
}
//停止信号
//在时钟线为高电平时,数据线由低向高跳变.
void StopI2C(void)
{   SDA=0;
    NOP;
    SCK=1;
    NOP;
    SDA=1;
}

//发送一个字节.
bit SendChar(unsigned char SendData)
{   unsigned char i;
    bit ACK;
    for(i=0;i<8;i++)
    {   if((SendData<<i)&0x80)SDA=1;
        else SDA=0;
        SCK=1;
        NOP;
        SCK=0;
        NOP;
    }
//发送一个字节后,读取来自I2C芯片的响应.
//即在发送完8个字节后,在第九个时钟内,SDA总线应为低电平,表示I2C芯片已经读取了数据.
//否则为高电平.即发送收败.
    SDA=1;
    SCK=1;
    NOP;
    ACK=SDA;
    SCK=0;
    NOP;
    return ACK;

}
//在读取完来自I2C的8位数据后,发出读取正确位.
//即发送一个低电平,表示已经读取到来自I2C的数据,并允许I2芯片发送下一字节.
void ACK(void)
{   SDA=0;
    NOP;
    SCK=1;
    NOP;
    SCK=0;
}
//在读取完来自I2C的8位数据后,发送不响应位.
//即发送一个高电平,表示已经读取完来自I2C的数据,并且不允许I2C发送下一字节.
void NAK(void)
{
    SDA=1;
    NOP;
    SCK=1;
    NOP;
    SCK=0;
}
//读入一个字节的数据.
unsigned char ReadChar(void)
{   unsigned char i,BackData;
    BackData=0;
    SDA=1;
    for(i=0;i<8;i++)
    {   SCK=1;
        nop;nop;nop;
        BackData=BackData<<1;
        if(SDA)BackData++;
        SCK=0;
    }
    return BackData;
}

//以下所有为测试使用...
//应注意,在读I2C芯片时,在发送完I2C片内地址后,
//一定要发送一个重开始信号,然后再发送读命令.

bit WriteI2C(unsigned char Address,unsigned char WriteData)
{   SENDSTART:
    StartI2C();
    if(SendChar(I2C_Address)) goto SENDSTART;
    SENDADD:
    if(SendChar(Address)){StartI2C;goto SENDADD;}
    SENDDATA:
    if(SendChar(WriteData)){StartI2C;goto SENDDATA;}
    if(SendChar(WriteData)){StartI2C;goto SENDDATA;}
    StopI2C();
    return 0;
}

unsigned char ReadI2C(unsigned char Address)
{   unsigned char BackData;
    ReadSTART:
    StartI2C();
    if(SendChar(I2C_Address)) goto ReadSTART;
    ReadADD:
    if(SendChar(Address)){StartI2C;goto ReadADD;}
    ReadSTART2:
    StartI2C();
    if(SendChar(I2C_Address+1)) goto ReadSTART2;
    BackData=ReadChar();
    ACK();
    BackData=ReadChar();
    NAK();
    StopI2C();
    return BackData;
}

void Delay(unsigned int ms)
{   unsigned int i,j;
    for(i=0;i<ms;i++)
    for(j=0;j<240;j++);
}

void main(void)
{   bit j;
    unsigned char i,BackData=0;
    unsigned char Address=0x00,ReadData=0x00;
    while(1)
    {   ResetI2C;
        ReadData=ReadI2C(Address);
        ReadData++;
        Delay(5);
        WriteI2C(Address,ReadData);
        Delay(5);
        Address++;Address++;

    }
}