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[color=#cc0033]串口电平[/color]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 <reg52.h>
#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;
}
}
}
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