DHT22.c
#include "DHT22.h"
#include "delay.h"
#include <stdio.h>
//Reset DHT11
void DHT22_Rst(void)
{
DHT22_IO_OUT(); //SET OUTPUT
DHT22_DQ_OUT=0; //GPIOA.0=0
delay_ms(30); //Pull down Least 800us
DHT22_DQ_OUT=1; //GPIOA.0=1
delay_us(30); //Pull up 20~40us
}
u8 DHT22_Check(void)
{
u8 retry=0;
DHT22_IO_IN();//SET INPUT
while (DHT22_DQ_IN&&retry<100)//DHT22 Pull down 40~80us
{
retry++;
delay_us(1);
};
if(retry>=100)
{
return 1;
}
else
retry=0;
while (!DHT22_DQ_IN&&retry<100)//DHT22 Pull up 40~80us
{
retry++;
delay_us(1);
};
if(retry>=100)
{
return 1;//chack error
}
return 0;
}
u8 DHT22_Read_Bit(void)
{
u8 retry=0;
while(DHT22_DQ_IN&&retry<100)//wait become Low level
{
retry++;
delay_us(1);
}
retry=0;
while(!DHT22_DQ_IN&&retry<100)//wait become High level
{
retry++;
delay_us(1);
}
delay_us(40);//wait 40us
if(DHT22_DQ_IN)
return 1;
else
return 0;
}
u8 DHT22_Read_Byte(void)
{
u8 i,dat;
dat=0;
for (i=0;i<8;i++)
{
dat<<=1;
dat|=DHT22_Read_Bit();
}
return dat;
}
u8 DHT22_Read_Data(u16 *temperature,u16 *humidity)
{
u8 buf[5];
u8 i;
DHT22_Rst();
if(DHT22_Check()==0)
{
for(i=0;i<5;i++)
{
buf[i]=DHT22_Read_Byte();
}
*humidity=((buf[0]*256)+buf[1])/10;
*temperature=((buf[2]*256)+buf[3])/10;
}
else
{
return 1;
}
return 0;
}
u8 DHT22_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_SetBits(GPIOA,GPIO_Pin_0);
DHT22_Rst();
return DHT22_Check();
}
DHT22.h
#ifndef __DHT22_H
#define __DHT22_H
#include "sys.h"
//Set GPIO Direction
#define DHT22_IO_IN() {GPIOA->CRL&=0XFFFF0FFF;GPIOA->CRL|=8<<12;} //PA3
#define DHT22_IO_OUT() {GPIOA->CRL&=0XFFFF0FFF;GPIOA->CRL|=3<<12;} //PA3
#define DHT22_DQ_OUT PAout(3)
#define DHT22_DQ_IN PAin(3)
u8 DHT22_Init(void); //Init DHT22
u8 DHT22_Read_Data(u16 *temperature,u16 *humidity); //Read DHT22 Value
u8 DHT22_Read_Byte(void);//Read One Byte
u8 DHT22_Read_Bit(void);//Read One Bit
u8 DHT22_Check(void);//Chack DHT22
void DHT22_Rst(void);//Reset DHT22
#endif
main.c
DHT22_Read_Data(&temperature,&humidity);