Wrong Temperature and Humidity Readings on DHT22

[fabiom91]

Following your TemperatureSensor example, I'm getting the wrong reading for temperature and humidity. I'm using a Sparkfun ESP8266 Thing Dev, a DHT22 Temperature and Humidity sensor with the DHT library from Adafruit (v1.4.4).

This is the code I used before without HomeKit to read temperature and humidity:

#include <DHT.h>

#define DHTPIN 4 // what pin we're connected to
#define DHTTYPE DHT22 // DHT 22  (AM2302)
DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino

//Variables
float hum;  //Stores humidity value
float temp; //Stores temperature value

void setup()
{
  Serial.begin(9600);
  dht.begin();
}

void loop()
{
    delay(2000);
    //Read data and store it to variables hum and temp
    hum = dht.readHumidity();
    temp= dht.readTemperature();
    //Print temp and humidity values to serial monitor
    Serial.print("Humidity: ");
    Serial.print(hum);
    Serial.print(" %, Temp: ");
    Serial.print(temp);
    Serial.println(" Celsius");
}

Which prints the correct temperature and humidity values:

Humidity: 58.90 %, Temp: 19.40 Celsius
Humidity: 58.90 %, Temp: 19.50 Celsius
Humidity: 58.90 %, Temp: 19.50 Celsius
...

Now in the Arduino-Homekit TemperatureSensor example (.ino file):

#include <Arduino.h>
#include <arduino_homekit_server.h>
#include "wifi_info.h"
//include the Arduino library for your real sensor here, e.g. <DHT.h>
#include <DHT.h>

#define DHTPIN 4 // what pin we're connected to
#define DHTTYPE DHT22 // DHT 22  (AM2302)
DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino

#define LOG_D(fmt, ...)   printf_P(PSTR(fmt "\n") , ##__VA_ARGS__);

float temperature_value;
float humidity_value;

void setup() {
  temperature_value = 0.0;
  humidity_value = 0.0;
    Serial.begin(115200);
    wifi_connect(); // in wifi_info.h
    my_homekit_setup();
}

void loop() {
    my_homekit_loop();
    delay(10);
}

//==============================
// Homekit setup and loop
//==============================

// access your homekit characteristics defined in my_accessory.c
extern "C" homekit_server_config_t config;
extern "C" homekit_characteristic_t cha_current_temperature;
extern "C" homekit_characteristic_t cha_humidity;

static uint32_t next_heap_millis = 0;
static uint32_t next_report_millis = 0;

void my_homekit_setup() {
    arduino_homekit_setup(&config);
}

void my_homekit_loop() {
    arduino_homekit_loop();
    const uint32_t t = millis();
    if (t > next_report_millis) {
        // report sensor values every 10 seconds
        next_report_millis = t + 10 * 1000;
        my_homekit_report();
    }
    if (t > next_heap_millis) {
        // show heap info every 5 seconds
        next_heap_millis = t + 5 * 1000;
        LOG_D("Free heap: %d, HomeKit clients: %d",
                ESP.getFreeHeap(), arduino_homekit_connected_clients_count());

    }
}

void my_homekit_report() {
  //Read data and store it to variables hum and temp
  temperature_value = dht.readTemperature();
  humidity_value = dht.readHumidity();
    cha_current_temperature.value.float_value = temperature_value;
  cha_humidity.value.float_value = humidity_value;
    LOG_D("Current temperature: %.1f", temperature_value);
  LOG_D("Current humidity: %.1f", humidity_value);
    homekit_characteristic_notify(&cha_current_temperature, cha_current_temperature.value);
  homekit_characteristic_notify(&cha_humidity, cha_humidity.value);
}

But I'm getting this output:

Current temperature: 9.7
Current humidity: 29.6
...
Current temperature: -9.7
Current humidity: 29.3
...

What am I doing wrong?

[Bighoneypot]

Dear, add pinMode(your DHTpin, INPUT); in setup();

On Thu, 8 Dec 2022, 10:41 Fabio Magarelli, @.***> wrote:

Following your TemperatureSensor example, I'm getting the wrong reading for temperature and humidity. I'm using a Sparkfun ESP8266 Thing Dev, a DHT22 Temperature and Humidity sensor with the DHT library from Adafruit (v1.4.4).

This is the code I used before without HomeKit to read temperature and humidity:

include

define DHTPIN 4 // what pin we're connected to

define DHTTYPE DHT22 // DHT 22 (AM2302)

DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino //Variablesfloat hum; //Stores humidity valuefloat temp; //Stores temperature value void setup() { Serial.begin(9600); dht.begin(); } void loop() { delay(2000); //Read data and store it to variables hum and temp hum = dht.readHumidity(); temp= dht.readTemperature(); //Print temp and humidity values to serial monitor Serial.print("Humidity: "); Serial.print(hum); Serial.print(" %, Temp: "); Serial.print(temp); Serial.println(" Celsius"); }

Which prints the correct temperature and humidity values:

Humidity: 58.90 %, Temp: 19.40 Celsius Humidity: 58.90 %, Temp: 19.50 Celsius Humidity: 58.90 %, Temp: 19.50 Celsius ...

Now in the Arduino-Homekit TemperatureSensor example (.ino file):

include

include

include "wifi_info.h"//include the Arduino library for your real sensor here, e.g.

include

define DHTPIN 4 // what pin we're connected to

define DHTTYPE DHT22 // DHT 22 (AM2302)

DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino

define LOG_D(fmt, ...) printf_P(PSTR(fmt "\n") , ##__VA_ARGS__);

float temperature_value;float humidity_value; void setup() { temperature_value = 0.0; humidity_value = 0.0; Serial.begin(115200); wifi_connect(); // in wifi_info.h my_homekit_setup(); } void loop() { my_homekit_loop(); delay(10); } //==============================// Homekit setup and loop//============================== // access your homekit characteristics defined in my_accessory.cextern "C" homekit_server_config_t config;extern "C" homekit_characteristic_t cha_current_temperature;extern "C" homekit_characteristic_t cha_humidity; static uint32_t next_heap_millis = 0;static uint32_t next_report_millis = 0; void my_homekit_setup() { arduino_homekit_setup(&config); } void my_homekit_loop() { arduino_homekit_loop(); const uint32_t t = millis(); if (t > next_report_millis) { // report sensor values every 10 seconds next_report_millis = t + 10 1000; my_homekit_report(); } if (t > next_heap_millis) { // show heap info every 5 seconds next_heap_millis = t + 5 1000; LOG_D("Free heap: %d, HomeKit clients: %d", ESP.getFreeHeap(), arduino_homekit_connected_clients_count());

} } void my_homekit_report() { //Read data and store it to variables hum and temp temperature_value = dht.readTemperature(); humidity_value = dht.readHumidity(); cha_current_temperature.value.float_value = temperature_value; cha_humidity.value.float_value = humidity_value; LOG_D("Current temperature: %.1f", temperature_value); LOG_D("Current humidity: %.1f", humidity_value); homekit_characteristic_notify(&cha_current_temperature, cha_current_temperature.value); homekit_characteristic_notify(&cha_humidity, cha_humidity.value); }

But I'm getting this output:

Current temperature: 9.7 Current humidity: 29.6 ... Current temperature: -9.7 Current humidity: 29.3 ...

What am I doing wrong?

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[fabiom91]

Dear, add pinMode(your DHTpin, INPUT); in setup(); …

Oh 🤦‍♂️ I added dht.begin() in the setup() and now it's working. Apologies.

[Bighoneypot]

Dear, add pinMode(your DHTpin, INPUT); in setup(); …

Oh 🤦‍♂️ I added dht.begin() in the setup() and now it's working. Apologies.

Dear @fabiom91 I noticed that too but from my smartphone I forgot to write it 🤣