这个单片机程序有问题，求大神指教

课设\KESHE13021037.C(21): error C231: '_write_IIC': redefinition
#define INT8U unsigned char
#define INT16U unsigned int
#include <reg51.h>
#include <intrins.h>
#include <string.h>
#include <stdio.h>
sbit SCL=P2^0;
sbit SDA=P2^1;
#include "I2C.h"
#define SUB_DEV_ADDR 0x80;
sbit K1 = P1^1;
sbit K2 = P1^3;
sbit K3 = P1^5;
sbit K4 = P1^7;
write_IIC(INT8U ch,INT8U dat);
void delay_ms(INT16U x) {INT8U t; while(x--) for(t = 0; t<120; t++);}
void write_IIC(INT8U ch,INT8U dat)
{
IIC_Start();
IIC_writebyte(SUB_DEV_ASSR);
if(ch==1) IIC_writebyte(CHW1);else
if(ch==2) IIC_writebyte(CHW2);
IIC_WriteByte(dat);
IIC_Stop();
}
void main()
{
INT8U i=0,CH1_Dat=0x00,CH2_Dat=0x00;
Write_IIC(1,0x00); Write_IIC(2,0x00);
while(1)
{
if(K1==0)
{
delay_ms(10);
if(K1==0)
{
if(CH1_Dat<0xFF) CH1_Dat++; Write_IIC(1,CH1_Dat);
}
}
if(K2==0)
{
delay_ms(10);
if(K2==0)
{
if(CH1_Dat<0x00) CH1_Dat--; Write_IIC(1,CH1_Dat);
}
}
if(K3==0)
{
delay_ms(10);
if(K3==0)
{
if(CH2_Dat<0xFF) CH2_Dat++; Write_IIC(2,CH2_Dat);
}
}
if(K4==0)
{
delay_ms(10);
if(K4==0)
{
if(CH2_Dat!=0x00)) CH2_Dat--; Write_IIC(2,CH2_Dat);
}
}
}
}
}
}