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下面是用普通C51實現的I2C基本電平模擬函數和通用函數。 

/*  電平模擬函數和基本讀寫函數 
    void IIC_Start(void); 
    void IIC_Stop(void); 
    void SEND_0(void); 
    void SEND_1(void); 
    bit Check_Acknowledge(void); 
    void Write_Byte(uchar b)reentrant; 
    bit Write_N_Bytes(uchar *buffer,uchar n)reentrant; 
    bit Read_N_Bytes(uchar SlaveAdr,uchar n,uchar *buffer); 
    uchar Read_Byte(void)reentrant; 
*/ 

    #include<string.h> 
    #include<reg52.h> 
    #include<intrins.h> 
    #include"aiic_51.h" 

    sbit SCL=P1^6; 
    sbit SDA=P1^7; 

    void DELAY(uint t) 
    { 
        while(t!=0) 
            t--; 
    } 

    void IIC_Start(void) 
    { 
        //啟動I2C總線的函數 ， 當SCL為高電平時使SDA產生一個負跳變 
        SDA=1; 
        SCL=1; 
        DELAY(DELAY_TIME); 
        SDA=0; 
        DELAY(DELAY_TIME); 
        SCL=0; 
        DELAY(DELAY_TIME); 
    } 

    void IIC_Stop(void) 
    { 
        //終止I2C總線，當SCL為高電平時使SDA產生一個正跳變 
        SDA=0; 
        SCL=1; 
        DELAY(DELAY_TIME); 
        SDA=1; 
        DELAY(DELAY_TIME); 
        SCL=0; 
        DELAY(DELAY_TIME); 
    } 

    void SEND_0(void) 
    { 
        //發(fā)送0，在SCL為高電平時使SDA信號為低 
        SDA=0; 
        SCL=1; 
        DELAY(DELAY_TIME); 
        SCL=0; 
        DELAY(DELAY_TIME); 
    } 

    void SEND_1(void) 
    { 
        //發(fā)送1，在SCL為高電平時使SDA信號為高 
        SDA=1; 
        SCL=1; 
        DELAY(DELAY_TIME); 
        SCL=0; 
        DELAY(DELAY_TIME); 
    } 

    bit Check_Acknowledge(void) 
    { 
        //發(fā)送完一個字節(jié)后檢驗設備的應答信號 
        SDA=1; 
        SCL=1; 
        DELAY(DELAY_TIME/2); 
        F0=SDA; 
        DELAY(DELAY_TIME/2); 
        SCL=0; 
        DELAY(DELAY_TIME); 
        if(F0==1) 
            return FALSE; 
        return TRUE; 
    } 

    void Write_Byte(uchar b)reentrant 
    { 
        //向IIC總線寫一個字節(jié) 
        uchar i; 
        for(i=0;i<8;i++) 
            if((b<<i)&0x80) 
                SEND_1(); 
            else 
                SEND_0(); 
    } 

    bit Write_N_Bytes(uchar *buffer,uchar n)reentrant 
    { 
        //向I2C總線寫n個字節(jié) 
        uchar i; 
        IIC_Start(); 

        for(i=0;i<n;i++) 
        { 
            Write_Byte(buffer[i]); 
            if(!Check_Acknowledge()) 
                { 
                    IIC_Stop(); 
                    return(i==n); 
                } 
        } 

        IIC_Stop(); 
        return TRUE; 
    } 

    uchar Read_Byte(void)reentrant 
    { 
        //從I2C總線讀一個字節(jié) 
        uchar b=0,i; 
        for(i=0;i<8;i++) 
        { 
            SDA=1;    //釋放總線 
            SCL=1;    //接受數據 
            DELAY(10); 
            F0=SDA; 
            DELAY(10); 
            SCL=0; 
            if(F0==1) 
                { 
                    b=b<<1; 
                    b=b|0x01; 
                } 
            else 
                b=b<<1; 
        } 
        return b; 
    } 

    bit Read_N_Bytes(uchar SlaveAdr,uchar n,uchar *buffer) 
    { 
        //從I2C總線讀n個字節(jié) 
        uchar i; 
        IIC_Start(); 
        Write_Byte(SlaveAdr);        //向總線發(fā)送接收器地址 
        if(!Check_Acknowledge())     //等待接收器應答信號 
            return FALSE; 
        for(i=0;i<n;i++) 
            { 
                buffer[i]=Read_Byte(); 
                if(i!=n) 
                    SEND_0();    //發(fā)送應答 
                else 
                    SEND_1();    //發(fā)送非應答 
            } 
        IIC_Stop(); 
        return TRUE; 
    } 
  
  

使用上述代碼，你可以在51上用P1口模擬I2C