Stc89c52/90c516rd/89c516rd DHT11 temperature and humidity sensor drive code

1. Hardware

STC89C52/90C516RD/89C516RD etc.
Crystal oscillator ：11.0592M
Memory configuration ：

Memory Model by small, Selecting other does not work properly .

2. Code

dht11.h

#ifndef __DHT11_H
#define __DHT11_H 
#include "reg52.h" 

#ifndef uchar
#define uchar unsigned char
#endif

#ifndef uint
#define uint unsigned int
#endif

IO Operation function  
sbit DHT11_DQ_OUT=P1^4; 	

extern uchar idata rec_dat[15]; 	
uchar get_dht11_data(uchar *temp, uchar *humi);
#endif

dht11.c

#include <dht11.h>
#include <intrins.h>
#include "delay.h"

uchar idata rec_dat[15] = "";

uchar idata humi_data_H = 0;
uchar idata humi_data_L = 0;
uchar idata temp_data_H = 0;
uchar idata temp_data_L = 0;
uchar idata check_data = 0;

/*************************************************** *  Delay subfunction  *  Time delay 10us ****************************************************/

static void delay_10us()		//@11.0592MHz
{
    
	uchar i;

	i = 2;
	while (--i);
}

static void delay_30us()		//@11.0592MHz
{
    
	uchar i;

	i = 11;
	while (--i);
}


/*  Function description ： obtain dht11 A byte   Parameters ：void  Return value ： Acquired dht11 One byte of data  */
static uchar get_dht11_byte(void)
{
       
	uchar i = 0;
	uchar time_out = 0;
	uchar temp = 0;
	uchar dht11_byte_data = 0;
	for(i=0;i<8;i++)	   
	{
    
		time_out=0;	
		while((!DHT11_DQ_OUT)&&time_out++ <= 5); /*  each bit Before the data starts , Both last about 50us Low level of  */
		if(time_out == 6) break;  /*  Timeout exit  */
		delay_30us();   /*  exceed 30us High level after , Indicates that the bit by 1 */
		temp=0;
		if(DHT11_DQ_OUT)temp=1;
		time_out=0;
		while((DHT11_DQ_OUT)&&time_out++ <= 200);
		 
		if(time_out==200)break;
		
		dht11_byte_data<<=1;
		dht11_byte_data|=temp;        //0
	}
	return dht11_byte_data;
}


/*  Function description ： obtain DHT11 Temperature and humidity data   Parameters ：*temp  temperature  *humi  humidity   Return value ： Return on success 0  Failure to return 1 */
uchar get_dht11_data(uchar *temp, uchar *humi)
{
    
	uchar time_out;
	uchar temp1 = 0;
	
	DHT11_DQ_OUT=0;
	delay_ms(20);   /*  At least pull down the host 18ms */
	DHT11_DQ_OUT=1; 
	delay_10us();
	delay_10us();
	delay_10us();
	delay_10us();	/*  The main engine is pulled up 20-40us */
	
	time_out = 0;
	
	while(!DHT11_DQ_OUT && time_out++ <= 5); /*  wait for DHT11 Respond  */
	if(time_out == 6)   return 1; /*  Timeout exit ,sht11 Not responding  */
	else   /* DHT11 Respond to  */
	{
    
		time_out=0;	 
		while((!DHT11_DQ_OUT)&&time_out++ <= 5);  /*  wait for DHT11 The response is complete , About time delay is required 80us */
		if(time_out == 6)  return 1; /*  Timeout exception  */
		time_out=0;
		while((DHT11_DQ_OUT)&&time_out++ <= 5);
		if(time_out == 6)  return 1; /*  Timeout exception  */ 
		humi_data_H=get_dht11_byte();
		humi_data_L=get_dht11_byte();
		temp_data_H=get_dht11_byte();
		temp_data_L=get_dht11_byte();
		check_data =get_dht11_byte();
		DHT11_DQ_OUT=1;
		// data verification  
		temp1 = (humi_data_H+humi_data_L+temp_data_H+temp_data_L);
		if(temp1 == check_data)
		{
    
			*humi = humi_data_H;
			*temp = temp_data_H;
			rec_dat[0] = temp_data_H/10 + '0';
			rec_dat[1] = temp_data_H%10 + '0';
			rec_dat[2] = ' ';
			rec_dat[3] = humi_data_H/10 + '0';
			rec_dat[4] = humi_data_H%10 + '0';
			rec_dat[5] = '\0';
		}
	 }
	return 0;
}

If you have any problems with the code, please refer to DHT11 Data book or message , The common module or chip driver code will be updated from time to time .