I2C总线是2条线总线.数据线SDA,时钟线SCL.结构简单.

AT24C04是具有I2C总线接口的EEPROM.大小为512*8bit.单片机AT89S52本身不具有I2C总线结口,所以可编写程序用并行端口模拟I2C总线协议读写AT24C04.

多个设备通信的重点(1.电平的区别，如串口通信中PC与单片机通信,PC机串口电平值为+12V~-12V，单片机为TTL电平0V~+5V.，所以要用电平转换芯片转电平.2，通信协议.(串口通信协议))

具体的协议内容与数据格式可查资料.

代码如下:

#include

#define WriteDeviceAddress 0xa0

#define ReadDeviceAddress 0xa1

sbit SCL = P3^4;

sbit SDA = P3^5;

sbit DOG = P0^0;

sbit PP = P0^1;

sbit DOG1 = P0^7;

void DelayMs(unsigned int number)

{

unsigned ｃｈａｒ tmp;

for(;number!=0;number--,DOG1=!DOG1)

{

for(tmp=112;tmp!=0;tmp--)

{

}

}

}

void Start()

{

SDA = 1;

DelayMs(1);

SCL = 1;

DelayMs(1);

SDA = 0;

DelayMs(1);

SCL = 0;

DelayMs(1);

}

bit Write8bit(unsigned ｃｈａｒ input)

{

unsigned ｃｈａｒ tmp;

for(tmp =8;tmp!=0;tmp--)

{

SDA = (bit)(input&0x80);

DelayMs(1);

SCL = 1;

DelayMs(1);

SCL = 0;

DelayMs(1);

input = input << 1;

}

return 1;

}

bit TestAck()

{

bit ErrorBit;

SDA = 1;

DelayMs(1);

SCL = 1;

DelayMs(1);

ErrorBit = SDA;

DelayMs(1);

SCL = 0;

DelayMs(1);

return(ErrorBit);

}

void Stop()

{

SCL = 0;

DelayMs(1);

SDA = 0;

DelayMs(1);

SCL = 1;

DelayMs(1);

SDA = 1;

DelayMs(1);

}

void WriteI2C(unsigned ｃｈａｒ *Wdata, unsigned ｃｈａｒ RomAddress, unsigned ｃｈａｒ number)

{

Start();

Write8bit(WriteDeviceAddress);

TestAck();

Write8bit(RomAddress);

TestAck();

for(;number!=0;number--)

{

Write8bit(*Wdata);

TestAck();

Wdata++;

}

Stop();

DelayMs(1);

}

unsigned ｃｈａｒ Read8Bit()

{

unsigned ｃｈａｒ tmp,rbyte = 0;

for(tmp=8;tmp!=0;tmp--)

{

SCL = 1;

DelayMs(1);

rbyte = rbyte << 1;

DelayMs(1);

rbyte = rbyte|((unsigned ｃｈａｒ)(SDA));

SCL = 0;

DelayMs(1);

}

return(rbyte);

}

void Ack()

{

SDA = 0;

DelayMs(1);

SCL = 1;

DelayMs(1);

SCL = 0 ;

DelayMs(1);

SDA = 1;

DelayMs(1);

}

void NoAck()

{

SDA = 1;

DelayMs(1);

SCL = 1;

DelayMs(1);

SCL = 0 ;

DelayMs(1);

}

void ReadI2C(unsigned ｃｈａｒ* RamAddress,unsigned ｃｈａｒ RomAddress,unsigned ｃｈａｒ bytes)

{

Start();

Write8bit(WriteDeviceAddress);

TestAck();

Write8bit(RomAddress);

TestAck();

Start();

Write8bit(ReadDeviceAddress);

TestAck();

while(bytes != 1)

{

*RamAddress = Read8Bit();

Ack();

RamAddress++;

bytes--;

}

*RamAddress = Read8Bit();

NoAck();

Stop();

}

void main()

{

unsigned ｃｈａｒ writeByte[8] = {0xC0,0X34,0X12,0X22,0X11,0X01,0X00,0X00};

unsigned ｃｈａｒ readByte[8];

unsigned ｃｈａｒ *addw;

unsigned ｃｈａｒ *addr;

unsigned ｃｈａｒ i;

unsigned ｃｈａｒ ok = 0;

bit write = 1;

DOG = 1;

while(1)

{

if(write == 1)

{

addw = writeByte;

addr = readByte;

WriteI2C(addw,0x00,8);

ReadI2C(addr,0x00,8);

for(i=0;i<8;i++)

{

if(writeByte[i] == readByte[i])

{

ok++;

}

}

if(ok == 8)

{

DOG = 0; //一样P0.0亮

}

else

{

PP = 0; //不一样P0.1亮

}

write = 0;

}

}

}