我需要一个c语言代码可以实现89C51芯片和PCF8591之间I2C通讯读取光敏电阻输出的电压值并且判断当处于黑暗时将P1.0口置于高电平点亮LED

以下是一个简单的C语言代码，可以实现89C51芯片和PCF8591之间I2C通讯读取光敏电阻输出的电压值，并且判断当处于黑暗时将P1.0口置于高电平点亮LED。

#include <reg51.h>

#define SDA P2_0
#define SCL P2_1

sbit LED = P1 ^ 0;

void delay(int n)
{
    int i, j;
    for (i = 0; i < n; i++)
        for (j = 0; j < 100; j++)
            ;
}

void i2c_start()
{
    SDA = 1;
    SCL = 1;
    delay(1);
    SDA = 0;
    delay(1);
    SCL = 0;
    delay(1);
}

void i2c_stop()
{
    SDA = 0;
    SCL = 1;
    delay(1);
    SDA = 1;
    delay(1);
}

void i2c_write(unsigned char dat)
{
    unsigned char i;
    for (i = 0; i < 8; i++)
    {
        SDA = dat & 0x80;
        SCL = 1;
        dat <<= 1;
        SCL = 0;
    }
    SDA = 1;
    SCL = 1;
    delay(1);
    SCL = 0;
}

unsigned char i2c_read()
{
    unsigned char i, dat = 0;
    SDA = 1;
    for (i = 0; i < 8; i++)
    {
        SCL = 1;
        dat <<= 1;
        dat |= SDA;
        SCL = 0;
    }
    return dat;
}

unsigned char i2c_read_ack()
{
    unsigned char dat = i2c_read();
    SDA = 0;
    SCL = 1;
    delay(1);
    SCL = 0;
    return dat;
}

unsigned char i2c_read_nack()
{
    unsigned char dat = i2c_read();
    SDA = 1;
    SCL = 1;
    delay(1);
    SCL = 0;
    return dat;
}

void init_pcf8591()
{
    i2c_start();
    i2c_write(0x90); //写器件地址
    i2c_write(0x40); //发送控制字节
    i2c_stop();
}

unsigned char read_adc(unsigned char ch)
{
    unsigned char dat;
    i2c_start();
    i2c_write(0x90);           //写器件地址
    i2c_write(0x40 + ch);      //发送控制字节
    i2c_start();               //重新启动
    i2c_write(0x91);           //读器件地址
    dat = i2c_read_nack();     //读取数据
    i2c_stop();                //停止
    return dat;                //返回数据
}

void main()
{
    init_pcf8591();
    while (1)
    {
        unsigned char val = read_adc(0);
        if (val < 128)
            LED = 1;
        else
            LED = 0;
    }
}

注意，这里的代码仅供参考，实际使用需要根据具体硬件和软件环境进行修改。