C51用GY39光强检测通过串口通信CT连RXD，DR连TXD，用LCD1602显示代码

以下是基于C51单片机使用GY39光强检测器并通过串口通信将数据显示在LCD1602上的代码，你可以参考一下：

#include <reg51.h>
#include <stdio.h>

#define LCD1602_DB P0
sbit LCD1602_RS = P2^0;
sbit LCD1602_RW = P2^1;
sbit LCD1602_E = P2^2;

sbit CT = P3^0;
sbit DR = P3^1;

sbit LED = P1^0;

unsigned char LCD1602_Read_Busy()
{
    unsigned char sta;
    LCD1602_DB = 0xFF;
    LCD1602_RS = 0;
    LCD1602_RW = 1;
    do
    {
        LCD1602_E = 1;
        sta = LCD1602_DB;
        LCD1602_E = 0;
    }while(sta & 0x80);
    return sta;
}

void LCD1602_Write_Command(unsigned char cmd)
{
    LCD1602_Read_Busy();
    LCD1602_RS = 0;
    LCD1602_RW = 0;
    LCD1602_DB = cmd;
    LCD1602_E = 1;
    LCD1602_E = 0;
}

void LCD1602_Write_Data(unsigned char dat)
{
    LCD1602_Read_Busy();
    LCD1602_RS = 1;
    LCD1602_RW = 0;
    LCD1602_DB = dat;
    LCD1602_E = 1;
    LCD1602_E = 0;
}

void LCD1602_Init()
{
    LCD1602_Write_Command(0x38); //8位数据接口，2行显示，5x7点阵字符
    LCD1602_Write_Command(0x0C); //显示开，关游标，不闪烁
    LCD1602_Write_Command(0x06); //光标移动，不移动屏幕
    LCD1602_Write_Command(0x01); //清屏
}

void LCD1602_Show_String(unsigned char x, unsigned char y, unsigned char *str)
{
    unsigned char i = 0;
    if(x < 16 && y < 2)
    {
        if(y == 0)
            LCD1602_Write_Command(0x80 + x);
        else
            LCD1602_Write_Command(0xC0 + x);
        while(str[i] != '\0')
        {
            LCD1602_Write_Data(str[i]);
            i++;
        }
    }
}

void UART_Init()
{
    TMOD = 0x20;
    TH1 = 0xFD;
    TL1 = TH1;
    SCON = 0x50;
    TR1 = 1;
}

unsigned char UART_IsRxReady()
{
    return RI;
}

unsigned char UART_ReadByte()
{
    RI = 0;
    return SBUF;
}

void UART_WriteByte(unsigned char dat)
{
    SBUF = dat;
    while(TI == 0);
    TI = 0;
}

unsigned char GY39_ReadData(unsigned char reg_addr)
{
    unsigned char dat;
    CT = 0;
    DR = 1;
    DR = 0;
    UART_WriteByte(reg_addr);
    dat = UART_ReadByte();
    CT = 1;
    return dat;
}

void main()
{
    unsigned char str[16];
    unsigned char data;
    LCD1602_Init();
    UART_Init();
    while(1)
    {
        data = GY39_ReadData(0x10);
        LED = data > 128 ? 1 : 0; // 光强度大于128时点亮LED
        sprintf(str, "Light: %d", data);
        LCD1602_Show_String(0, 0, str);
        delay(500);
    }
}

注意：此代码仅供参考，具体实现可能需要根据实际情况进行修改。