Hertz:
Io uso questo sketch che ho preso da un sito:
//ReadHumTturDHT11alternate2
//ver 19Jly10
//This is a re-written DHT11/ DHT22 reading code.
//DHT stuff in subroutines.
//See for more information....
//http://sheepdogguides.som/arduino/ar3ne1humDHT11.htm
//N.B. "bit" is used in the narrow, computer "1 or 0"
// sense throughout.
//"DHT" from sensor's names: DHT11, DHT22.
//DHT aka Aosong AM2302, and there's an AM2303 which
//seems to be in the same family.
//Comments on this based on Aosong AM2302, aka DHT22, datasheet.
//Believed to generally apply to DHT11 as well, except in the
//case of the DHT11, I believe the second and fourth bytes are
//always zero.
//N.B.*
//The code WORKS... the comments may not yet be EXACTLY right.
//See the web-page cited above for latest news.
//This code works with a DHT11 humidity/ temperature sensing module
//from nuelectronics.com, complied with ver 0018 of the Arduino environment
//Sensor attached to P4 (nuelectonics shield)/ analog 0, aka digital 14.
//That "module", according to the
//nuelectronics site, and visual inspection simply provides for easy
//connection of an Aosong DHT11 unit to the nuelectronics datalogging
//shield. Only 3 wires are involved: Vcc, ground, and a single data
//line. One of the DHT11's 4 pins goes nowhere.
//You should not need to change anything except the next line to use
//the software with the sensor on a different line, or for a DHT22.
//Just "huffing" on the sensor from deeply filled lungs should show
//a near instant rise in humidity
//#define dht_PIN 0 //no ; here. deprecate ADC0...
//even though we are using it as a digital pin.
//Other parts of code restrict us to using
//ADC0-5, aka D14-19
#define dht_dpin 14 //no ; here. Set equal to channel sensor is on,
//where if dht_dpin is 14, sensor is on digital line 14, aka analog 0
byte bGlobalErr;//for passing error code back from complex functions.
byte dht_dat[4];//Array to hold the bytes sent from sensor.
void setup(){
InitDHT();//Do what's necessary to prepare for reading DHT
Serial.begin(9600);
delay(300);//Let system settle
Serial.println("Humidity and temperature\n\n");
delay(700);//Wait rest of 1000ms recommended delay before
//accessing sensor
}//end "setup()"
void loop(){
ReadDHT();//This is the "heart" of the program.
//Fills global array dht_dpin[], and bGlobalErr, which
//will hold zero if ReadDHT went okay.
//Must call InitDHT once (in "setup()" is usual) before
//calling ReadDHT.
//Following: Display what was seen...
switch (bGlobalErr){
case 0:
Serial.print("Current humdity = ");
Serial.print(dht_dat[0], DEC);
Serial.print(".");
Serial.print(dht_dat[1], DEC);
Serial.print("% ");
Serial.print("temperature = ");
Serial.print(dht_dat[2], DEC);
Serial.print(".");
Serial.print(dht_dat[3], DEC);
Serial.println("C ");
break;
case 1:
Serial.println("Error 1: DHT start condition 1 not met.");
break;
case 2:
Serial.println("Error 2: DHT start condition 2 not met.");
break;
case 3:
Serial.println("Error 3: DHT checksum error.");
break;
default:
Serial.println("Error: Unrecognized code encountered.");
break;
}//end "switch"
delay(800);//Don't try to access too frequently... in theory
//should be once per two seconds, fastest,
//but seems to work after 0.8 second.
}// end loop()
/Below here: Only "black box" elements which can just be plugged unchanged
unchanged into programs. Provide InitDHT() and ReadDHT(), and a function
one of them uses./
void InitDHT(){
//DDRC |= _BV(dht_PIN);//set data pin... for now... as output
//DDRC is data direction register for pins A0-5 are on
//PORTC |= _BV(dht_PIN);//Set line high
//PORTC relates to the pins A0-5 are on.
//Alternative code...
// if (dht_dpin-14 != dht_PIN){Serial.println("ERROR- dht_dpin must be 14 more than dht_PIN");};//end InitDHT
pinMode(dht_dpin,OUTPUT);// replaces DDRC... as long as dht_dpin=14->19
digitalWrite(dht_dpin,HIGH);//Replaces PORTC |= if dht_pin=14->19
}//end InitDHT
void ReadDHT(){
/Uses global variables dht_dat[0-4], and bGlobalErr to pass
"answer" back. bGlobalErr=0 if read went okay.
Depends on global dht_PIN for where to look for sensor./
bGlobalErr=0;
byte dht_in;
byte i;
// Send "start read and report" command to sensor....
// First: pull-down i/o pin for 18ms
digitalWrite(dht_dpin,LOW);//Was: PORTC &= ~_BV(dht_PIN);
delay(18);
delay(5);//TKB, frm Quine at Arduino forum
/*aosong.com datasheet for DHT22 says pin should be low at least
500us. I infer it can be low longer without any]
penalty apart from making "read sensor" process take
longer. */
//Next line: Brings line high again,
// second step in giving "start read..." command
digitalWrite(dht_dpin,HIGH);//Was: PORTC |= _BV(dht_PIN);
delayMicroseconds(40);//DHT22 datasheet says host should
//keep line high 20-40us, then watch for sensor taking line
//low. That low should last 80us. Acknowledges "start read
//and report" command.
//Next: Change Arduino pin to an input, to
//watch for the 80us low explained a moment ago.
pinMode(dht_dpin,INPUT);//Was: DDRC &= ~_BV(dht_PIN);
delayMicroseconds(40);
dht_in=digitalRead(dht_dpin);//Was: dht_in = PINC & _BV(dht_PIN);
if(dht_in){
bGlobalErr=1;//Was: Serial.println("dht11 start condition 1 not met");
return;
}//end "if..."
delayMicroseconds(80);
dht_in=digitalRead(dht_dpin);//Was: dht_in = PINC & _BV(dht_PIN);
if(!dht_in){
bGlobalErr=2;//Was: Serial.println("dht11 start condition 2 not met");
return;
}//end "if..."
/After 80us low, the line should be taken high for 80us by the
sensor. The low following that high is the start of the first
bit of the forty to come. The routine "read_dht_dat()"
expects to be called with the system already into this low./
delayMicroseconds(80);
//now ready for data reception... pick up the 5 bytes coming from
// the sensor
for (i=0; i<5; i++)
dht_dat[i] = read_dht_dat();
//Next: restore pin to output duties
pinMode(dht_dpin,OUTPUT);//Was: DDRC |= _BV(dht_PIN);
//N.B.: Using DDRC put restrictions on value of dht_pin
//Next: Make data line high again, as output from Arduino
digitalWrite(dht_dpin,HIGH);//Was: PORTC |= _BV(dht_PIN);
//N.B.: Using PORTC put restrictions on value of dht_pin
//Next see if data received consistent with checksum received
byte dht_check_sum =
dht_dat[0]+dht_dat[1]+dht_dat[2]+dht_dat[3];
/Condition in following "if" says "if fifth byte from sensor
not the same as the sum of the first four..."/
if(dht_dat[4]!= dht_check_sum)
{
bGlobalErr=3;
}//Was: Serial.println("DHT11 checksum error");
};//end ReadDHT()
byte read_dht_dat(){
//Collect 8 bits from datastream, return them interpreted
//as a byte. I.e. if 0000.0101 is sent, return decimal 5.
//Code expects the system to have recently entered the
//dataline low condition at the start of every data bit's
//transmission BEFORE this function is called.
byte i = 0;
byte result=0;
for(i=0; i< 8; i++){
//We enter this during the first start bit (low for 50uS) of the byte
//Next: wait until pin goes high
while(digitalRead(dht_dpin)==LOW);//Was: while(!(PINC & _BV(dht_PIN)));
//signalling end of start of bit's transmission.
//Dataline will now stay high for 27 or 70 uS, depending on
//whether a 0 or a 1 is being sent, respectively.
delayMicroseconds(30);//AFTER pin is high, wait further period, to be
//into the part of the timing diagram where a 0 or a 1 denotes
//the datum being send. The "further period" was 30uS in the software
//that this has been created from. I believe that a higher number
//(45?) would be more appropriate.
//Next: Wait while pin still high
if (digitalRead(dht_dpin)==HIGH)//Was: if(PINC & _BV(dht_PIN))
result |=(1<<(7-i));// "add" (not just addition) the 1
//to the growing byte
//Next wait until pin goes low again, which signals the START
//of the NEXT bit's transmission.
while (digitalRead(dht_dpin)==HIGH);//Was: while((PINC & _BV(dht_PIN)));
}//end of "for.."
return result;
}//end of "read_dht_dat()"
Prova a vedere se funziona.
niente da fare , sul monitor seriale mi dice error 1 condition not met
l'ho collegato cosi http://learning.grobotronics.com/images/Tutorials/dhtwiring.gif
solo che il pin 2 è collegato al pin A0
