集成电路总线IIC

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IIC为一个串行总线。单片机和IIC之间相连这数据线（CLK）和时钟线（SDA）。
IIC总线需通过上拉电阻接正电源，总线空闲时，为高电平。

注

上拉电阻的作用
1.让引脚在悬空（开漏）的状态下有确定的电平
2.增加驱动电流

这里写图片描述

void iic_start(){     SDA = 1;     SCL = 1;     delay_us(1);     SDA = 0;     delay_us(1);     SCL = 0;}void iic_stop(){      SDA = 0;      SCL = 1;      delay_us(1);      SDA = 1;      delay_us(1);      SCL = 0;}void iic_send_byte(unsigned char byte){      unsigned char i;      for(i = 0; i < 8; i++)       {               SDA = byte & 0x80;              SCL = 1;              delay_us(1);              SCL = 0;              byte <<= 1;        }        SCL = 1;        SDA = 1;        delay_us(1);        if(0 == SDA)        {             ack = 1;         }        else        {             ack = 0;         }        SCL = 0;//      return ack;}unsigned char iic_recv_byte(){      unsigned char i,a;      unsigned char temp = 0;      SDA = 1;      for(i = 0; i < 8; i++)      {                SCL = 0;              delay_us(1);              SCL = 1;              if(SDA)            {                     a = 0x01;             }            else            {                     a = 0;             }            temp |= (a << 7-i);            delay_us(1);        }        SCL = 0;        return temp;}void iic_ack(){      SDA = 0;      SCL = 1;      delay_us(1);      SCL = 0;}void iic_noack(){      SDA = 1;      SCL = 1;      delay_us(1);      SCL = 0;}unsigned char AT24C02_send_str(unsigned char devadd, unsigned char romadd, unsigned char *s, unsigned char num){      unsigned char i;      iic_start();      iic_send_byte(devadd);      if(0 == ack)        {             return FAIL;         }        iic_send_byte(romadd);        if(0 == ack)        {             return FAIL;         }        for(i = 0; i < num; i++)        {             iic_send_byte(*s);             if(0 == ack)             {                  return FAIL;             }             s++;         }        iic_stop();        return SUCC;}unsigned char AT24C02_rev_str(unsigned char devadd, unsigned char romadd, unsigned char *s, unsigned char num){       unsigned char i;      iic_start();      iic_send_byte(devadd);      if(0 == ack)      {            return FAIL;      }        iic_send_byte(romadd);        if(0 == ack)        {             return FAIL;         }        iic_start();        iic_send_byte(devadd+1);        for(i = 0; i < num - 1; i++)        {               *s = iic_recv_byte();              iic_ack();              s++;          }        *s = iic_recv_byte();        iic_noack();        iic_stop();        return SUCC;}void main(){    unsigned char test[11] = {'I','l','o','v','e','s','t','u','d','y','\0'};    unsigned char temp[11];    lcd_init();    AT24C02_send_str(0xae,100,test,11);    delay_ms(20);    AT24C02_rev_str(0xae,100,temp,11);    delay_ms(20);    lcd_string(1,2,temp);    while(1);}

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