51单片机用LCD1602显示温度、湿度、光度，分别写明DHT11头文件、LCD1602头文件、主程序。

DHT11头文件：

#ifndef _DHT11_H_
#define _DHT11_H_

#include <reg51.h>

sbit DHT11 = P2^0;

void DHT11_Delay(unsigned int i);
void DHT11_Start(void);
unsigned char DHT11_ReadData(void);

#endif

LCD1602头文件：

#ifndef _LCD1602_H_
#define _LCD1602_H_

#include <reg51.h>

sbit LCD1602_RS = P1^0;
sbit LCD1602_RW = P1^1;
sbit LCD1602_EN = P1^2;

void LCD1602_Delay(unsigned int i);
void LCD1602_WriteCmd(unsigned char cmd);
void LCD1602_WriteData(unsigned char dat);
void LCD1602_Init(void);
void LCD1602_Clear(void);
void LCD1602_SetCursor(unsigned char x, unsigned char y);
void LCD1602_WriteString(unsigned char x, unsigned char y, unsigned char *str);
void LCD1602_WriteChar(unsigned char x, unsigned char y, unsigned char dat);

#endif

主程序：

#include <reg51.h>
#include "DHT11.h"
#include "LCD1602.h"

void main()
{
    unsigned char temp_hum[5];
    unsigned char light;
    unsigned char str[16];

    LCD1602_Init();
    DHT11_Start();

    while(1)
    {
        temp_hum[0] = DHT11_ReadData();
        temp_hum[1] = DHT11_ReadData();
        temp_hum[2] = DHT11_ReadData();
        temp_hum[3] = DHT11_ReadData();
        temp_hum[4] = DHT11_ReadData();

        light = P0;

        LCD1602_Clear();

        sprintf(str, "Temp:%dC Hum:%d%%", temp_hum[0], temp_hum[2]);
        LCD1602_WriteString(0, 0, str);

        sprintf(str, "Light:%d", light);
        LCD1602_WriteString(0, 1, str);

        DHT11_Delay(500);
    }
}