DHT22 works with Photon, not Xenon & Argon

Firmware
1

I have successfully gotten the DHT22 to work on my Photon, but for both the Xenon & Argon it always return zeros.

I’ve identified from forum postings the #include statement needs to be changed and there is a fix best retrieved by using piettetech_dht and ensuring it has the January 2019 update. Both are true.

I am sending the data via the .publish to ThinkSpeak (not using serial as in the examples if that makes a difference) and I’ve tried float, int & double declarations for the variables.

I assume there is something simple I am missing.

2

For debugging it's always best to keep things as simple as possible - i.e. try serial printing first and when that is working move on.

3

Generally, I would agree with you. But in this case I have working code, I am just changing hardware.

This is an environmental \ context problem of some kind.

4

The DHT22 definitely works with Xenon - I have tried the sensor myself. Could you share how you are connecting it and the simple code just to get temperature and humidity from the sensor?

5

This is the code. (cannibalized from another post). Beyond confirming I have the January 2019 version of PietteTech_DHT.h, I’ve added delays between reads. The voltage displays with correct data, the other two are always zero. When I run it on the photon (battery commented out) observations start up after a cycle or two.

// This #include statement was automatically added by the Particle IDE.
#include <PietteTech_DHT.h>

// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#define DHTPIN 2     // what pin we're connected to
#define DHTTYPE DHT22	  

 PietteTech_DHT(DHTPIN, DHTTYPE);
SYSTEM_MODE(AUTOMATIC);
void setup() {

	dht.begin();
}

void loop() {
// Wait a few seconds between measurements.
	delay(2000);
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a 
// very slow sensor)

        delayMicroseconds(40);
    double DHT_temp = dht.getTempFarenheit();
        delayMicroseconds(40);
    double DHT_humid = dht.getHumidity();
    
    // Now we'll take some readings...

    //Temperature
    int temperature_analog = DHT_temp; // read DHT sensor
    float temperature_percentage = (10 + ( (temperature_analog/50) ) );  
    
    //Humidity
    int humidity_analog = DHT_humid; // read DHT sensor
    float humidity_percentage = (10 + ( (humidity_analog/50) ) );

     //Battery Life   
    if(BATT){
        float voltage = analogRead(BATT) * 0.0011224;
        Particle.publish("voltage", String(voltage),60,PUBLIC);
  
    // Send a publish devices...
        delay(4000);  
    Particle.publish("DHT_temperature", String(temperature_analog),60,PUBLIC);
  //  Particle.publish("DHT_temp_percentage", String(temperature_percentage),60,PUBLIC);
         delay(4000);     
    Particle.publish("DHT_humidity", String(humidity_analog),60,PUBLIC);
 //   Particle.publish("DHT_humid_percentage", String(humidity_percentage),60,PUBLIC);
}
6

Hi Will, what library did you use? thanks!

7

I just looked at this and it was the Seeed_DHT11 library as I was using the DHT11 supplied in the Grove Starter Kit for Particle Mesh and not the DHT22. Sorry to mislead. I had a look at the application I used for the Photon and that was PIETTETECH_DHT library. I just tried the @Moors7 BLE example with a Xenon - DHT11 reading which appears to have a 1 in 3 read failure - BLE works fine!