void delay()

{; ;}

void delay1ms ( uint z )
{
uint x, y;
for ( x = z; x > 0; x -- )
for ( y = 110; y > 0; y -- );
}

I2C啟動(dòng)：在SCL為高電平期間，SDA出現(xiàn)下降沿

void start_I2C ( ) /
{
sda = 1;
delay ();
scl= 1;
delay ();
sda = 0;
delay ();
}

I2C停止：在SCL高電平期間，SDA上產(chǎn)生一上升沿

void stop_I2C () //停止
{
sda = 0;
delay ();
scl = 1;
delay ();
sda = 1;
delay ();
}

總線初始化：將總線拉高以釋放總線

void init_I2C ()
{
sda = 1;
delay ();
scl = 1;
delay ();
}

應(yīng)答信號(hào)：在SCL高電平期間，SDA被從設(shè)備拉低表示應(yīng)答

void response ()//應(yīng)答
{
uchar i;
scl = 1;
delay ();
while ( ( sda == 1 ) && ( i < 250 ) ) i ++; // i < 255這里只是表示沒(méi)有應(yīng)答時(shí)，若i > 255就直接退出，才不至于死循環(huán)。
scl = 0;
delay ();
}

寫(xiě)一個(gè)字節(jié)：只有在SCL低電平期間，SDA上的高電平或低電平才可以變化

void write_byte ( uchar date )
{
uchar i, temp;
temp = date;
for ( i = 0; i < 8; i ++ )
{
temp = temp << 1;　　　　//將最高位移入CY里面
scl = 0;
delay ();
sda = CY;
delay ();
scl = 1;
delay ();
}

scl = 0;
delay ();
sda = 1;
delay ();

}

讀一個(gè)字節(jié)：

uchar read_byte ()
{
uchar i, k;
scl = 0;
delay ();
sda = 1;
delay ();
for ( i = 0; i < 8; i ++ )
{
scl = 1;
delay ();
k = ( k << 1 ) " sda; //也是從最高位開(kāi)始讀
scl = 0;
delay ();
}
return k;

}