单片机I2C驱动子程序

晶振11.0592M/********************************************************************/
/*******************I2C模拟通信及AT24C02底层驱动程序****************/
/********************************************************************/
//AT24C02
//delayus: 延时约5us
void delayus()
{
;;
}
//i2c:init I2C总线初始化
void i2c_init()
{
SCL = 1;
delayus();
SDA = 1;
delayus(); 
}
//lcd:start   起始信号
void start()
{
SCL = 1;
SDA = 1;
delayus();
SDA = 0;
delayus();
}
//i2c:stop 停止信号
void stop()
{
SCL = 1;
SDA = 0;
delayus();
SDA = 1;
delayus(); 
}
//i2c:ack 从机应答信号
void ack()
{
uchar i = 0;
//在SCL = 1时，读取SDA的数据判忙
SCL = 1;
delayus();
while((SDA == 1)&& i < 250)
i++;
//判忙之后，等待发送数据/命令
SCL = 0;
delayus();
}
//nack: 主机非应答信号
void nack()
{
//主机发送非应答信号1
SCL = 1;
delayus();
SDA = 1;
delayus();
//等待发送数据/命令
SCL = 0;
delayus();
}
//write:byte 写一个字节数据
void write_byte(uchar date)
{ //从最高位发送
uchar i, temp;
temp = date;
for(i = 0; i < 8; i++)
{
temp <<= 1;
SCL = 0;
delayus();
SDA = CY;
delayus();
SCL = 1;
delayus();
SCL = 0;
delayus();
}
//等待从机应答
SCL = 0;
delayus();
SDA = 1;//置1,等待从机应答0
delayus();
}
//read:byte   读一个字节数据
uchar read_byte()
{
uchar i, j, k;
SCL = 0;
delayus();
for(i =  0; i < 8; i++)
{
SCL = 1;
delayus();
j = SDA;
k = (k << 1) | j;
delayus();
SCL = 0;
delayus();
}
delayus();
return (k);
}
//write:AT24C02   写AT24C02
void write_c02(uchar address, uchar date)
{
start();
write_byte(write_add);
ack();
write_byte(address);
ack();
write_byte(date);
ack();
stop();
delay(12); 
}
//read:AT24C02 读AT24C02
uchar read_c02(uchar add)
{
uchar date = 0;
start();
write_byte(write_add);
ack();
write_byte(add);
ack();
start();
write_byte(read_add);
ack();
date = read_byte();
nack();
return (date);
}