HELP !! DHT22 Sensor returns -999

Using Arduino Sensors
1

Hello

Iam using DHT22 sensor with arduino it works fine but this morning it returns just the -999 values for both Temprature and Humidity

Please does anybody have ana idea about that problem ?

2

post your code!

3

The value -999 indicates there is an error.

Which version of the library are you using?

4

here's my code :

/**
 * Example code for using a microchip mrf24j40 module to send and receive
 * packets using plain 802.15.4
 * Requirements: 3 pins for spi, 3 pins for reset, chip select and interrupt
 * notifications
 * This example file is considered to be in the public domain
 * Originally written by Karl Palsson, karlp@tweak.net.au, March 2011
 */
#include <SPI.h>
#include <mrf24j.h>
#include <dht.h>

dht DHT;

#define DHT22_PIN 7

const int pin_reset = 6;
const int pin_cs = 52; // default CS pin on ATmega8/168/328
const int pin_interrupt = 5; // default interrupt pin on ATmega8/168/328

Mrf24j mrf(pin_reset, pin_cs, pin_interrupt);

long last_time;
long tx_interval = 1000;

void setup() {
 
  SPI.setBitOrder(MSBFIRST) ;
    SPI.setDataMode(SPI_MODE0);
    SPI.begin();
  Serial.begin(115200);
  
  mrf.reset();
  mrf.init();
  
  mrf.set_pan(0x1234);
  // This is _our_ address
  mrf.address16_write(0x6002); 

  // uncomment if you want to receive any packet on this channel
  mrf.set_promiscuous(true);
  
   //uncomment if you want to enable PA/LNA external control
  //mrf.set_palna(true);
  
  // uncomment if you want to buffer all PHY Payload
  mrf.set_bufferPHY(true);

  attachInterrupt(pin_interrupt, interrupt_routine, CHANGE); // interrupt 0 equivalent to pin 2(INT0) on ATmega8/168/328
  last_time = millis();
  interrupts();
}

void interrupt_routine() {
    mrf.interrupt_handler(); // mrf24 object interrupt routine
}

int H;
String str;
char HH[3];

void loop() {
    mrf.check_flags(&handle_rx, &handle_tx);
    unsigned long current_time = millis();
    if (current_time - last_time > tx_interval) {
        last_time = current_time;
        
         uint32_t start = micros();
    int chk = DHT.read22(DHT22_PIN);
    uint32_t stop = micros();
    
   
//    // DISPLAY DATA
    Serial.print(DHT.humidity, 1);
    Serial.print(",\t");
    Serial.print(DHT.temperature, 1);
    Serial.print(",\t");
    Serial.print(stop - start);
    Serial.println();
    
    H=int(DHT.humidity);
    str=String(H);
    str.toCharArray(HH,3); 
    
     Serial.print(HH);
     Serial.println();
    
        Serial.println("txxxing...");
        mrf.send16(0x6001, HH);
        
    }
}

void handle_rx() {
    Serial.print("received a packet ");Serial.print(mrf.get_rxinfo()->frame_length, DEC);Serial.println(" bytes long");
    
    if(mrf.get_bufferPHY()){
      Serial.println("Packet data (PHY Payload):");
      for (int i = 0; i < mrf.get_rxinfo()->frame_length; i++) {
          Serial.print(mrf.get_rxbuf()[i]);
      }
    }
    
    Serial.println("\r\nASCII data (relevant data):");
    for (int i = 0; i < mrf.rx_datalength(); i++) {
        Serial.write(mrf.get_rxinfo()->rx_data[i]);
    }
    
    Serial.print("\r\nLQI/RSSI=");
    Serial.print(mrf.get_rxinfo()->lqi, DEC);
    Serial.print("/");
    Serial.println(mrf.get_rxinfo()->rssi, DEC);
}

void handle_tx() {
    if (mrf.get_txinfo()->tx_ok) {
        Serial.println("TX went ok, got ack \n");
    } else {
        Serial.print("TX failed after \n ");Serial.print(mrf.get_txinfo()->retries);Serial.println(" retries\n");
    }
}

Iam using DHTlib VERSION: 0.1.13

5

What is the value of the pullup resistor on the dht data pin?

6

I don't know how to get the value of the pullup resistor :frowning:

7

digital multimeter, even a $5 one is good enough these days
or
read the color code on the resistor?

8

It was a leading question. I half expected a reply of "I don't have a pullup resistor". But, I guess there are many answers to any question.
So, let me ask, do you have a pullup resistor on the DHT data line?