EEPROM（electrically erasable and programmable read-only memory），就是一個(gè)可以讀寫(xiě)數(shù)據(jù)的存儲(chǔ)器件，斷電后數(shù)據(jù)還保存著，一般用來(lái)存儲(chǔ)一些用戶設(shè)置的參數(shù)，攝像頭模組上也會(huì)用它保存OTP的數(shù)據(jù)。

以AT24C08為例，如下代碼通過(guò)GPIO產(chǎn)生IIC通信信號(hào)，進(jìn)行讀寫(xiě)。

代碼示例iic.h

#ifndef _IIC_H_
#define  _IIC_H_
#include "def.h"

#define  AT24C08_ADDRDRESS    0xa0
#define  true  1
#define  false   0
#define PAGE1   0xa0
#define PAGE2   0xa2
#define PAGE3   0xa4
#define PAGE4   0xa6
#define  IIC_CLOCK_HIGH           rGPEDAT |= (1<<14)
#define  IIC_CLOCK_LOW            rGPEDAT &= ~(1<<14)
#define  IIC_DATA_HIGH            rGPEDAT |= (1<<15)
#define  IIC_DATA_LOW             rGPEDAT &= ~(1<<15)
#define  SET_IIC_DATA_INPUT       rGPECON &= ~(3<<30)
#define  SET_IIC_DATA_OUTPUT      rGPECON |= (1<<30)

void iic_init(void);
U8  i2c_write(U8  device_address, U8  memory_address , U8 data);
U8  i2c_read(U8  device_address,  U8  memory_address, U8 *data);
U8  i2c_page_read(U8  device_address,  U8  memory_address, U8 *destination,U32 size);
U8  i2c_page_write(U8  device_address, U8 memory_address , U8 *source,U32 size);
U8  i2c_largepage_write(U8  device_address, U8 memory_address , U8 *source,U32 size);
void i2c_test(void);

#endif

iic.c

#include "2440addr.h"
#include "def.h"
#include "uart.h"
#include "iic.h"
//#include "timer.h"

#define   DELAY_DECIMUS_MS  100


void delayus( U32 time)
{
    U32 i,j;
    for ( i=0; i<time; i++)
    {
        for(j=0;j<DELAY_DECIMUS_MS;j++)
        {
        }   
    }             
}


void iic_init(void)
{
    /* config  GPE14, GPE15 as output*/
    rGPECON &=(~((3<<30)|(3<<28)));
    rGPECON |=(1<<30)|(1<<28);
    /* SDA,SCL 默認(rèn)為高電平 */
    rGPEDAT |= ((1<<15)|(1<<14));
    rGPEUP |= ((1<<15)|(1<<14));
    delayus(1);
}   


void i2c_start(void)
{   
    IIC_DATA_HIGH; 
    delayus(1);
    IIC_CLOCK_HIGH;
    delayus(1);
    IIC_DATA_LOW;   
    delayus(1);
    IIC_CLOCK_LOW;
}

void  i2c_stop(void)
{     
    SET_IIC_DATA_OUTPUT;
    delayus(1);
    IIC_DATA_LOW;         
    delayus(1);  
    IIC_CLOCK_HIGH;   
    delayus(1);  
     IIC_DATA_HIGH;     
    delayus(1);      
}   

U8  check_ack(void)
{
    /* ack */    
    U8  ret;
    U8 ucErrTime=0; 
    SET_IIC_DATA_INPUT;
    delayus(1); 
    IIC_CLOCK_HIGH; //negative edge clock data out of each device
    delayus(1);
    
    while(rGPEDAT&(1<<15))
    {   
        ucErrTime++;                    //時(shí)間累加
        ret = false;             
        if(ucErrTime>250)                     //如果時(shí)間大于250
        {
            i2c_stop();                         //調(diào)用IIC停止子函數(shù)
            return ret;                         //程序返回值0
        }
    }
     
    ret = true;
    IIC_CLOCK_LOW; 
    delayus(1);  
    SET_IIC_DATA_OUTPUT; 
    delayus(1);
    return ret;
}    

void send_no_ack(void)
{
    delayus(1);   
    IIC_CLOCK_LOW;  //positive edge clock data into eachEEPROM 
    delayus(1); 
    SET_IIC_DATA_OUTPUT;//發(fā)送數(shù)據(jù)時(shí)與上升沿同步
    IIC_DATA_HIGH;           /* 發(fā)送高電平no ack */
    delayus(2); 
    IIC_CLOCK_HIGH;
    delayus(1); 
    IIC_CLOCK_LOW;
    delayus(1);
}   
    


void  data_write(U8 data)
{
    U8 i;
    SET_IIC_DATA_OUTPUT; 
    delayus(1);
              
    /* data transmit */    
    for (i = 0; i< 8; i++)
    {
        if(data&(1<<(7-i)))//發(fā)送數(shù)據(jù)時(shí)與上升沿同步
        {
            IIC_DATA_HIGH;
        }
        else
        {
            IC_DATA_LOW;
        }  
        delayus(1);
        IIC_CLOCK_HIGH ;      
        delayus(1);  
        IIC_CLOCK_LOW ;
        delayus(1);
    }
      
    IIC_DATA_HIGH;
    delayus(1); 
    // UartPuts(" data write over!\n");
}   


void  data_read(U8  *data )
{
    U8 i;   
    IIC_DATA_HIGH;
    delayus(1); 
    SET_IIC_DATA_INPUT;
    delayus(1); 

    /* data reas */    
    for (i = 0 ; i< 8; i++)
    {
        IIC_CLOCK_LOW;
        delayus(1); 
        IIC_CLOCK_HIGH;  
        delayus(1); 

        if(rGPEDAT&(1<<15))//接收數(shù)據(jù)時(shí)與下降沿同步
        {   
            (*data) |=(1<<(7-i)) ;
        }   
        else
        {
            (*data) &=~(1<<(7-i)) ;
        }
    }
      
    IIC_CLOCK_LOW;
    delayus(1); 
    SET_IIC_DATA_OUTPUT; 
    //  Uart_Printf("----  %4x \n",*data); 
      
}   

U8  i2c_write(U8  device_address, U8 memory_address , U8 data)
{
    U8  write_addr;
    U8  ack_flag;
    U8  ret;
      
    /* start */
    i2c_start();
    /* write address transmit */    
    data_write(device_address);
    /* ack */    
    ack_flag = check_ack();
    //ack_flag = 0;
      
    if(!ack_flag)
    {
        ret =  false;
        UartPuts(" write  i2c  device address  no  ack!\n");
        goto  i2c_stop;
    }
      
    /* write address transmit */    
    data_write(memory_address);  
    /* ack */    
    ack_flag = check_ack();
      
    if(!ack_flag)
    {       
        ret =  false;
        UartPuts(" write  memory  address  no  ack!\n");
        while(1);
        goto  i2c_stop;
    }    
      
    /* write data transmit */  
    data_write(data);

    /* ack */    
    ack_flag = check_ack();
      
    if(!ack_flag)
    {
        ret =  false;
        UartPuts(" write  data   no  ack!\n");
        goto  i2c_stop;
    }
    else
    {
        ret =  true;
    }   
           
i2c_stop:
    i2c_stop();
    delayus(1000);  //延時(shí)等待STOP信號(hào)生效(10ms)
    return ret; 
}

U8  i2c_dummy_write(U8  device_address, U8 memory_address )
{
    U8  write_addr;
    U8  ack_flag;
    U8  ret;

    /* start */
    i2c_start();

    /* write address transmit */    
    data_write(device_address);

    /* ack */    
    ack_flag = check_ack();
      
    if(!ack_flag)
    {
        ret =  false;
        UartPuts(" dummy write  i2c  device address  no  ack!\n");
        goto  i2c_stop;
    }

    /* write address transmit */    
    data_write(memory_address);

    /* ack */    
    ack_flag = check_ack();

    if(!ack_flag)
    {       
        ret =  false;
        UartPuts(" dummy write  memory  address  no  ack!\n");
        goto  i2c_stop;
    }     
    /* write data transmit */  
    else
    {
        ret =  true;
        return ret; 
    }   
           
i2c_stop:
    i2c_stop();
    return ret; 
}


U8  i2c_read(U8  device_address,  U8  memory_address, U8 *data)
{
    U8  read_addr;          
    U8  ack_flag;     
    U8  ret;

    ret = i2c_dummy_write( device_address , memory_address);

    if(!ret)
    {
        ret =  false;
        return ret;      
    }   

    i2c_start();

    read_addr =  device_address |1;

    data_write(read_addr);

    ack_flag = check_ack();

    if(!ack_flag)
    {
        ret =  false;
        UartPuts(" i2c_read write  i2c  device address  no  ack!\n");
        goto  i2c_read_stop;
    }

    data_read(data);

    send_no_ack();    

    ret =  true;

    i2c_read_stop:
    i2c_stop();
    return ret;    
     
}       

U8  i2c_page_read(U8  device_address,  U8  memory_address, U8 *destination,U32 size)
{
    int i;
    for(i=0;i<size;i++)
        i2c_read(device_address,memory_address+i,destination+i);

}
U8  i2c_page_write(U8  device_address, U8 memory_address , U8 *source,U32 size)
{
    int i;
    for(i=0;i<size;i++)
    {
        i2c_write(device_address,memory_address+i,source[i]);
        //Uart_Printf("write %d\n",i);
    }
}

U8  i2c_largepage_write(U8  device_address, U8 memory_address , U8 *source,U32 size)
{
    int i;
    int n,m;
    if(size>256)
    Uart_Printf("Size illegal\n");
    //assert(size<=256);//判斷參數(shù)合法性

    n=size/16;      //寫(xiě)入的小頁(yè)數(shù)
    m=size%16;    //寫(xiě)入小頁(yè)后剩余的個(gè)數(shù)
    for(i=0;i<n;i++)
        i2c_page_write(device_address,(memory_address+16*i),(source+16*i),16);
    for(i=0;i<m;i++)
        i2c_write(device_address,(memory_address+16*n+i),*(source+16*n+i));
}

void i2c_test(void)
{
    U8 flag;

    U8  write_data;
    U8  read_data;
    U8 i,j;
    i=1;
    j=1;
      
    #if 0       
    UartPuts(" Begin to write!\n");

    for(i=1;i<10;i++,j++)
    {
        flag = i2c_write(AT24C02_ADDRDRESS,i,j);

        if(flag)    
            UartPuts(" write i2c ok!\n");
        else
            UartPuts(" write i2c failed!\n");  

        Delay_DMS(1000);

        flag = i2c_read(AT24C02_ADDRDRESS,i,&read_data);


        if(flag)
        {    
            Uart_Printf(" read  i2c ok! %4x \n",read_data); 
            //UartPutch(0x30+read_data); 
            //UartPuts(" \n");
            //Uart_Printf("%4x",read_data);
        }    
        else
        {
            UartPuts(" read  i2c failed!\n"); 
        } 

        Delay_DMS(500);     
    }    
    #endif 



    flag = i2c_read(AT24C08_ADDRDRESS,1,&read_data);


    if(flag)
    {    
        Uart_Printf("---- read  i2c ok! %4x \n",read_data); 
    }    
    else
    {
        UartPuts(" read  i2c failed!\n"); 
    } 

    delay1us(500);     
}