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Nodemcu arduino + DHT22 read problem

PostPosted: Sat Mar 26, 2016 5:41 am
by Hydro
Hi

I just buy nodemcu version 3 and i want to use them with DHT22 sensor.

My DHT22 is connect to D4 and 3.3v+gnd from another source than nodemcu.

Is can upload sketch without problem :

Code: Select all/* DHTServer - ESP8266 Webserver with a DHT sensor as an input
 
   Based on ESP8266Webserver, DHTexample, and BlinkWithoutDelay (thank you)
 
   Version 1.0  5/3/2014  Version 1.0   Mike Barela for Adafruit Industries
*/
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <aREST.h>
#include <DHT.h>
#define DHTTYPE DHT22
#define DHTPIN  2
 
const char* ssid     = "Freebox-A40088";
const char* password = "wifi_passwrd";
 
ESP8266WebServer server(80);
 
// Initialize DHT sensor
// NOTE: For working with a faster than ATmega328p 16 MHz Arduino chip, like an ESP8266,
// you need to increase the threshold for cycle counts considered a 1 or 0.
// You can do this by passing a 3rd parameter for this threshold.  It's a bit
// of fiddling to find the right value, but in general the faster the CPU the
// higher the value.  The default for a 16mhz AVR is a value of 6.  For an
// Arduino Due that runs at 84mhz a value of 30 works.
// This is for the ESP8266 processor on ESP-01
DHT dht(DHTPIN, DHTTYPE, 11); // 11 works fine for ESP8266
 
float humidity, temp_f;  // Values read from sensor
String webString="";     // String to display
// Generally, you should use "unsigned long" for variables that hold time
unsigned long previousMillis = 0;        // will store last temp was read
const long interval = 2000;              // interval at which to read sensor
 
void handle_root() {
  server.send(200, "text/plain", "Hello from the weather esp8266, read from /temp or /humidity");
  delay(100);
}

 void gettemperature() {
  // Wait at least 2 seconds seconds between measurements.
  // if the difference between the current time and last time you read
  // the sensor is bigger than the interval you set, read the sensor
  // Works better than delay for things happening elsewhere also
  unsigned long currentMillis = millis();
 
  if(currentMillis - previousMillis >= interval) {
    // save the last time you read the sensor
    previousMillis = currentMillis;   
 
    // Reading temperature for humidity takes about 250 milliseconds!
    // Sensor readings may also be up to 2 seconds 'old' (it's a very slow sensor)
    humidity = dht.readHumidity();          // Read humidity (percent)
    temp_f = dht.readTemperature();     // Read temperature as Fahrenheit
    // Check if any reads failed and exit early (to try again).
    if (isnan(humidity) || isnan(temp_f)) {
      Serial.println("Failed to read from DHT sensor!");
      return;
    }
  }
}

void setup(void)
{
  // You can open the Arduino IDE Serial Monitor window to see what the code is doing
  Serial.begin(115200);  // Serial connection from ESP-01 via 3.3v console cable
  dht.begin();           // initialize temperature sensor
 
  // Connect to WiFi network
  WiFi.begin(ssid, password);
  Serial.print("nr nrWorking to connect");
 
  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("DHT Weather Reading Server");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
   
  server.on("/", handle_root);
 
  server.on("/temp", [](){  // if you add this subdirectory to your webserver call, you get text below :)
    gettemperature();       // read sensor
    webString=""+String((float)temp_f)+"";   // Arduino has a hard time with float to string
    server.send(200, "text/plain", webString);            // send to someones browser when asked
  });
 
  server.on("/humidity", [](){  // if you add this subdirectory to your webserver call, you get text below :)
    gettemperature();           // read sensor
    webString=""+String((float)humidity)+"";
    server.send(200, "text/plain", webString);               // send to someones browser when asked
  });
 
  server.begin();
  Serial.println("HTTP server started");
}
 
void loop(void)
{
  server.handleClient();
}
 



But every time is try to go to url/temp i've got "nan". I try every pin number, try to change DHT, try to change nodemcu but same problem. I use DHT library from arduino.

It's like problem with pin but i don't find the right number.

Is someone have a solution ? Thank

Re: Nodemcu arduino + DHT22 read problem

PostPosted: Mon Mar 28, 2016 5:57 am
by Hydro
Someone use dht22 with nodemcu v3 ?

Re: Nodemcu arduino + DHT22 read problem

PostPosted: Mon Mar 28, 2016 6:33 am
by krzychb
Hi Hydro,

In case of such issues I typically start over from the simplest available sketch from examples provided with library.
For working example of use of dht22 with nodemcu v3 please check out this description.

If you still have issues then post particular DHT library name that you use.


Good luck,

Krzysztof

Re: Nodemcu arduino + DHT22 read problem

PostPosted: Mon Mar 28, 2016 11:05 am
by Hydro
Thank ! On nodemcu v3 pin number is 'D4' not '4'.