用labwindows写的i2c程序.txt

TWI一主多从实战程序片段

HRESULT CVIFUNC I2C_Start(void)
{
    HRESULT __result = S_FALSE;
    int i;
    unsigned char ack;
    for (i = 0; i < I2C_waitStartDelay;i ++) {
        ack = I2C_GetSDA();//释放数据总线读数据总线 
        I2C_SetSCL();//首先拉高SCL, 保证SDA在SCL=1时跳变,拉高时钟(必须在SDA=1时)
        I2C_ClrSDA();//首先拉低SDA.必须按次序！！！
        I2C_ClrSCL();//然后拉低SCL,构成I2C从机内部中断并唤醒
        if (ack) {//测试成功！！！总线已释放
            __result = S_OK;//
            break;
        }
    }
    if (__result == S_OK)
    {
        Hot_I2CErrorState = I2C_START;//已发送起始条件
    }
    else
    {
        Hot_I2CErrorState = -1;//未发送起始条件
        I2C_Stop ();
    }
    return __result;
}

HRESULT CVIFUNC I2C_ReStart(unsigned char addrss)
{
    HRESULT __result;
//入口：SDA=SCL=0
    I2C_SetSDA();//首先拉高SDA, 这样才能保证在SCL=1时SDA下跳构成再次复位条件即复位
    I2C_SetSCL();//然后拉高SCL, 保证SDA在SCL=1时跳变,拉高时钟(必须在SDA=1时)
    I2C_ClrSDA();//首先拉低SDA.必须按次序！！！
    I2C_ClrSCL();//然后拉低SCL,构成I2C从机内部中断并唤醒
    I2C_ReadWriteByte (addrss | 1);//强行发送I2C读地址,SDA=SCL=0
    __result =I2C_GetAck();//取从机ACK信号
    if (__result == S_OK) 
    {
        Hot_I2CErrorState = I2C_MT_SLA_ACK;//已发送SLA+W,且已接收ACK
    }
    else
    {
        Hot_I2CErrorState = I2C_MT_SLA_NACK;//已发送SLA+W,且未接收ACK
        I2C_Stop ();
    }
    return __result;
}

void CVIFUNC I2C_Stop (void)
{
    I2C_ClrSCL();
    I2C_ClrSDA();
      I2C_SetSCL();//在SCL为高时准备Stop信号,拉高时钟(必须在SDA=1时,故本例形成Stop())
      I2C_SetSDA();//STOP信号结束
}

void CVIFUNC I2C_WriteAck(unsigned char ack) 
{
    if (ack) {
        I2C_ClrSDA();//给从机ACK信号
    }
    else
    {
        I2C_SetSDA();//给从机nACK信号 
    }
    I2C_SetSCL();//拉高时钟信号,拉高时钟(必须在SDA=1时)
    I2C_ClrSCL();//拉低时钟信号,防止START信号产生
    I2C_ClrSDA();//给从机ACK信号
}


HRESULT CVIFUNC I2C_GetAck(void)
{
    HRESULT __result = S_FALSE;
    int i;
    for (i = 0; i < I2C_waitAckDelay; i ++)
    {
        if (I2C_GetSDA() == 0) //释放数据总线读数据总线
        {
            __result = S_OK;
            break;
        }
    }
    I2C_SetSCL();//拉高时钟(必须在SDA=1时)???
    I2C_ClrSCL();//拉低时钟
    I2C_ClrSDA();//保证SDA=SCL=0///pwy（拉低SDA便于发送停止喜欢）
    return __result;//SDA=1,SCL=0
}

/*-----------------------------------------------------------
    I2C一体化读写程序
-------------------------------------------------------------*/
unsigned char CVIFUNC I2C_ReadWriteByte(unsigned char value)
{
    int i;
    for (i = 0; i < 8; i ++)//每个字节8位
    {
        if (value >= 0x80) //D7位=1
        {
             value <<= 1;//I2C协议先出D7位
            I2C_SetSDA();
            if (I2C_GetSDA())//GetSDA()内带释放数据总线SetSDA()
            {
                value ++;//读回1位I2C数据1
            }
        }
        else//D7=0
        {
             value <<= 1;//I2C协议先出D7位 
            I2C_ClrSDA();//写入1位I2C数据0
        }
        I2C_SetSCL();//拉高I2C时钟
        I2C_ClrSCL();//拉低I2C时钟
    }
    I2C_ClrSDA();//保证出口SDA=SCL=0
    return value;//返回数据
}

unsigned char CVIFUNC I2C_ReadByte (unsigned char ack)
{
    unsigned char value;
    value = I2C_ReadWriteByte (0xff);//取数据
    I2C_WriteAck(ack);//向从机发送ACK/nACK信号  
    return value;//返回接收数据
}

unsigned short CVIFUNC I2C_ReadWord (unsigned char ack)
{
    unsigned short value;
    unsigned char ch, cl;
    cl = I2C_ReadByte (I2C_ACK);
    if (ack) ch = I2C_ReadByte (I2C_ACK);
    else ch = I2C_ReadByte (I2C_nACK);
    value = (ch << 8) | cl;
    return value;
}

void CVIFUNC I2C_ReadBlock (unsigned char *str, int size)
{
    int i;
    for (i = 0; i < size; i ++)
    {
        if (i == size - 1) 
        {
            str[i] = I2C_ReadByte(I2C_nACK);
        }
        else
        {
            str[i] = I2C_ReadByte(I2C_ACK);
        }
    }
}

HRESULT CVIFUNC I2C_WriteByte (unsigned char value)
{
    HRESULT __result = S_FALSE;
    I2C_ReadWriteByte (value);//写数据,SDA=SCL=0 
    __result = I2C_GetAck();//取从机ACK信号
    if (__result == S_OK) 
    {
        Hot_I2CErrorState = I2C_MT_DATA_ACK;//已发送I2DAT 中的数据字节，且已接收ACK
    }
    else
    {
        Hot_I2CErrorState = I2C_MT_DATA_NACK;//已发送I2DAT 中的数据字节，且未接收ACK
        I2C_Stop();
    }
    return __result;
}

HRESULT CVIFUNC I2C_WriteWord (unsigned short value)
{
    HRESULT __result = S_FALSE;
    unsigned char ch, cl;
    ch = value  >> 8;
    cl = value & 0xff;
    __result = I2C_WriteByte (cl);
    if (__result == S_OK)
    {
        __result = I2C_WriteByte (ch);
    }
    return __result;
}

HRESULT CVIFUNC I2C_WriteBlock (unsigned char *str, int size)
{
    HRESULT __result = S_FALSE;
    int i;
    for (i = 0; i < size; i ++)
    {
        __result = I2C_WriteByte(str[i]);
        if (__result != S_OK) break; 
    }
    return __result;
}