使用wiringpi編寫C程序：

如下程序借鑒了網(wǎng)上一老外的程序，忘了原帖地址在哪。

#include?

#include?

#include?

#include?

#define?MAX_TIME?85

#define?DHT11PIN?7

#define?ATTEMPTS?5?????????????????//retry?5?times?when?no?response

int?dht11_val[5]={0,0,0,0,0};

int?dht11_read_val(){

uint8_t?lststate=HIGH;?????????//last?state

uint8_t?counter=0;

uint8_t?j=0,i;

for(i=0;i<5;i++)

dht11_val[i]=0;

//host?send?start?signal

pinMode(DHT11PIN,OUTPUT);??????//set?pin?to?output

digitalWrite(DHT11PIN,LOW);????//set?to?low?at?least?18ms

delay(18);

digitalWrite(DHT11PIN,HIGH);???//set?to?high?20-40us

delayMicroseconds(40);

//start?recieve?dht?response

pinMode(DHT11PIN,INPUT);???????//set?pin?to?input

for(i=0;i

{

counter=0;

while(digitalRead(DHT11PIN)==lststate){?????//read?pin?state?to?see?if?dht?responsed.?if?dht?always?high?for?255?+?1?times,?break?this?while?circle

counter++;

delayMicroseconds(1);

if(counter==255)

break;

}

lststate=digitalRead(DHT11PIN);?????????????//read?current?state?and?store?as?last?state.

if(counter==255)????????????????????????????//if?dht?always?high?for?255?+?1?times,?break?this?for?circle

break;

//?top?3?transistions?are?ignored,?maybe?aim?to?wait?for?dht?finish?response?signal

if((i>=4)&&(i%2==0)){

dht11_val[j/8]<<=1;?????????????????????//write?1?bit?to?0?by?moving?left?(auto?add?0)

if(counter>16)??????????????????????????//long?mean?1

dht11_val[j/8]|=1;??????????????????//write?1?bit?to?1

j++;

}

}

//?verify?checksum?and?print?the?verified?data

if((j>=40)&&(dht11_val[4]==((dht11_val[0]+dht11_val[1]+dht11_val[2]+dht11_val[3])&?0xFF))){

printf("RH:%d,TEMP:%d\n",dht11_val[0],dht11_val[2]);

return?1;

}

else

return?0;

}

int?main(void){

int?attempts=ATTEMPTS;

if(wiringPiSetup()==-1)

exit(1);

while(attempts){????????????????????????//you?have?5?times?to?retry

int?success?=?dht11_read_val();?????//get?result?including?printing?out

if?(success)?{??????????????????????//if?get?result,?quit?program;?if?not,?retry?5?times?then?quit

break;

}

attempts--;

delay(2500);

}

return?0;

} 上述程序保存為.c文件后編譯成可執(zhí)行文件，運行后會在屏幕打印溫度和濕度。

程序中的數(shù)據(jù)接收處理部分細節(jié)如下：

if((i>=4)&&(i%2==0)){?????????//前3次分別是：1低電平，2高電平(即響應(yīng)信號)，3低電平(即數(shù)據(jù)第一個低電平)

//i%2==0?是因為每次都是循環(huán)讀取低電平和高電平，每次要循環(huán)2次才讀出一個bit處理

dht11_val[j/8]<<=1;???????//讀到后，j/8可以限制一個數(shù)的8個位，左移1位自動補0，相當于讀出0

if(counter>16)????????????//counter計數(shù)如果超過16，則高電平長，應(yīng)讀1.

dht11_val[j/8]|=1;????//故再將上面數(shù)與1位或，使最后一位變成1

j++;??????????????????????//j++8個換成下一個數(shù)據(jù)

}

if((j>=40)&&(dht11_val[4]==((dht11_val[0]+dht11_val[1]+dht11_val[2]+dht11_val[3])&?0xFF))){

//這其中(dht11_val[0]+dht11_val[1]+dht11_val[2]+dht11_val[3])&?0xFF)是將5個數(shù)相加，和1與。

//目的是防止讀出數(shù)據(jù)都為0，和為0，0和1與后得0，所以if判斷條件不成立，返回讀取失敗碼。

//如果讀出數(shù)據(jù)是不為0的正常數(shù)據(jù)，和1與后還得原數(shù)。

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