Arduino thermometer and humidity display with 7 segment LED display I want to use an Arduino Uno, a seven segment LED display (four digits) and the SevSeg library, to see temperature and humidity (alternatively). 

First of all I try this code:

  #define COMMON_ANODE 1
  #define COMMON_CATODE 0
  #include "DHT.h"
  #define DHTPIN A5     // pin analogico che legge i dati
  #define DHTTYPE DHT22   // DHT 22  (AM2302)
  #include "SevSeg.h"

  // Crea un'istanza dell'oggetto
  SevSeg sevseg;
  DHT dht(DHTPIN, DHTTYPE);
  unsigned long timer; // the timer
  unsigned long INTERVAL = 5000; // the repeat interval (30 seconds)

  int segA = 6;   // Undicesimo PIN del display 7Segment x 4
  int segB = 2;   // Settimo PIN del display 7Segment x 4
  int segC = 10;  // Quarto PIN del display 7Segment x 4
  int segD = 12;  // Secondo PIN del display 7Segment x 4
  int segE = 13;  // Primo PIN del display 7Segment x 4
  int segF = 5;   // Decimo PIN del display 7Segment x 4
  int segG = 9;   // Quinto PIN del display 7Segment x 4
  int segDP = 11; // Terzo PIN del display 7Segment x 4

  int digit1 = 7; // Dodicesimo PIN - PWM che Accende il primo digit
  int digit2 = 4; // Nono PIN - PWM che Accende il secondo digit 
  int digit3 = 3; // Ottavo PIN - PWM che Accende il terzo digit 
  int digit4 = 8; // Sesto PIN - PWM che Accende il quarto digit

  void setup() 
  {
    dht.begin();
    int numberOfDigits = 4; //Numero di cifre del display

    // Inizializzo i PIN
    sevseg.Begin(COMMON_CATODE,digit1,digit2,digit3,digit4,segA,segB,segC,segD,segE,segF,segG,segDP);
    // Imposto la luminosità (valore da 0 a 100)
    sevseg.Brightness(90);
    timer = millis(); // start timer
  }

  void loop() 
  {
    if ((millis()-timer) &gt; INTERVAL) {
      // Reset the timer and get/display the current temperature
      timer += INTERVAL;
      // Leggo dal sensore la temperatura
      float t = dht.readTemperature();
      float h = dht.readHumidity();
      //La converto in un numero intero a 4 cifre
      int a=t*100;
      sevseg.NewNum(a,2);
    }
        sevseg.PrintOutput();   
  }


And it works very well!

But I cant see temperature (first) AND humidity (after) and again temperature (first) AND humidity (after)...

I have tried many ways but... nothing!! Can you help me?
You need to maintain a state which tells your program whether you are displaying the temperature or the humidity.  Every time the timer expires you need to change from one state to the other, and then display the relevant value depending on what the state is.

Something like:

bool displaying = false; // false = temperature, true = humidity

void loop() {
    if ((millis()-timer) &gt;= INTERVAL) {
        timer = millis();
        display = !display; // Switch between display values

        if (display) {
            float h = dht.readHumidity();
            sevseg.NewNum(h * 100, 2);
        } else {
            float t = dht.readTemperature();
            sevseg.NewNum(t * 100, 2);
        }
    }
    sevseg.PrintOutput();   
}