DHT11's data on MAX7219 reads 0

Question

I want print data from a DHT11 (temperature and humidity) on a MAX7219 LED display but it only shows 0. Serial monitor, on the other hand, shows both humidity and temperature which means that my circuit works just fine and there's something wrong with code. Could anyone please point out what needs to be fixed to make it work? Thanks. Here is the code

#include <WiFi.h>
#include <NTPClient.h>
#include <DHT.h> 
#include <WiFiUdp.h>
#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
//#define HARDWARE_TYPE MD_MAX72XX::GENERIC_H
#define MAX_DEVICES 4
#define CLK_PIN   5 
#define DATA_PIN  7 
#define CS_PIN    6 
MD_Parola Display = MD_Parola(HARDWARE_TYPE, DATA_PIN, CLK_PIN, CS_PIN, MAX_DEVICES);
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP);
const char* ssid     = "6666";
const char* password = "6666";
String Time, hour, minute;
String Formatted_date;
long currentMillis = 0;
long previousMillis = 0;
int interval = 1000;
#define DHTPIN  A2         /*Signal pin for DHT11 Sensor*/
#define DHTTYPE    DHT11  
DHT dht(DHTPIN, DHTTYPE);
void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print("Connecting.");
  }
  Serial.println("");
  Serial.println("WiFi connected.");
  timeClient.begin();
  timeClient.setTimeOffset(0);
Display.begin();
  Display.setIntensity(0);
  Display.displayClear();
dht.begin();
   Serial.println("Status\tHumidity (%)\tTemperature (C)");
}
void loop()
 {
   obtainTime();
}
void obtainTime() {
  while(!timeClient.update()) {
    timeClient.forceUpdate();
  }
  currentMillis = millis();
  if (currentMillis - previousMillis > interval)  {
previousMillis = millis();
Formatted_date = timeClient.getFormattedDate();
Serial.println(Formatted_date);
hour = Formatted_date.substring(11, 13);
minute = Formatted_date.substring(14, 16);
Time = hour + ":" + minute;
Serial.println(Time);
Display.setTextAlignment(PA_CENTER);
Display.print(Time);
delay(3000);
// The DHT11 returns at most one measurement every 3s
  float h = dht.readHumidity();
  //Read the moisture content in %.
  float t = dht.readTemperature();
  //Read the temperature in degrees Celsius
Serial.println(t);
Serial.println(h);
Display.setTextAlignment(PA_CENTER);
Display.print(t);
delay(5000);
Display.displayClear();
}
}

Andrew Coz · Answer 1 · 2023-10-02T05:35:33.940

It turned out that MD_Parola can't handle floats directly. I fixed the problem by converting the floats t and h into strings using dtostrf()

 float h = dht.readHumidity();
 float t = dht.readTemperature();
char temp_result[6];
dtostrf(t,2,1,temp_result);
char hum_result[6];
dtostrf(h,2,0,hum_result);
Serial.println(t);
Serial.println(h);
Display.setTextAlignment(PA_CENTER);
//Display.print(temp_result);
Display.print((String)temp_result+" "+"C");
delay(5000);
//Display.print(hum_result);
Display.print((String)hum_result+" "+"%");
delay(5000);

DHT11's data on MAX7219 reads 0

1 Answers1