C51进行I²C通信

I²C（Inter IC Bus）是由 Philips 推出的数据总线协议。

#include

void display(unsigned int n)

{

unsigned char i;

char table[]={

0x3f,0x06,0x5b,0x4f,

0x66,0x6d,0x7d,0x07,

0x7f,0x6f,0x77,0x7c,

0x39,0x5e,0x79,0x71

};

P2 = 0 << 2;

P0 = table[n%10];

for (i=0;i<25;i++);

P0 = 0;

P2 = 1 << 2;

P0 = table[n/10%10];

for (i=0;i<25;i++);

P0 = 0;

P2 = 2 << 2;

P0 = table[n/100%10];

for (i=0;i<25;i++);

P0 = 0;

P2 = 3 << 2;

P0 = table[n/1000%10];

for (i=0;i<25;i++);

P0 = 0;

}

// IIC bus

sbit SCL=P2^1;

sbit SDA=P2^0;

// 4 keys

sbit k1=P3^1;

sbit k2=P3^0;

sbit k3=P3^2;

sbit k4=P3^3;

void delay(unsigned int i)

{

while(i--);

}

void I2cStart()

{

SDA = 1;

delay(5);

SCL = 1;

delay(5);

SDA = 0;

delay(5);

}

void I2cStop()

{

SDA = 0;

delay(5);

SCL = 1;

delay(5);

SDA = 1;

}

void I2cSendByte(unsigned char n)

{

signed char i;

for (i=7;i>=0;i--)

{

SCL = 0;

delay(5);

SDA = 0x01 & (n>>i);

delay(5);

SCL = 1;

delay(5);

}

SCL = 0;

delay(5);

SDA = 1;

delay(5);

SCL = 1;

delay(5);

while((SDA==1)&&(i++<255));

SCL = 0;

delay(5);

}

unsigned char I2cReadByte()

{

unsigned char i,k;

SCL = 0;

delay(5);

SDA = 1;

delay(5);

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

{

SCL = 1;

delay(5);

k <<= 1;

k |= SDA;

SCL = 0;

delay(5);

}

delay(5);

return k;

}

int main()

{

unsigned char num=0;

while (1)

{

if(k1==0)

{

delay(1000);

if(k1==0)

{

I2cStart();

I2cSendByte(0xa0); // set chip

I2cSendByte(1); // set address 1

I2cSendByte(num); // set value

I2cStop();

}

while(!k1);

} else if(k2==0) {

delay(1000);

if(k2==0)

{

I2cStart();

I2cSendByte(0xa0); // set chip 0xa0

I2cSendByte(1); // set address 1

I2cStart();

I2cSendByte(0xa1); // set chip 0xa1

num=I2cReadByte(); // read byte

I2cStop();

}

while(!k2);

} else if(k3==0) {

delay(1000);

if(k3==0)

num++; // add 1

while(!k3);

} else if(k4==0) {

delay(1000);

if(k4==0)

num=0; // set 0

while(!k4);

}

display(num);

}

return 0;

}