My LCD info is called from an IF statement but since it's clock and temperature info i don't want to just show the information but update the information constantly in real time. i don't want to use (while) loop or any other "code-blocking".

Here's the whole code:

#include <OneWire.h>
#include <LiquidCrystal_I2C.h>
#include <DS3231.h>
#include <DallasTemperature.h>

#define ONE_WIRE_BUS 2
int Heater= 3;
int Switch1= 4;

Time t;
LiquidCrystal_I2C lcd(0x27, 16, 2);
DS3231  rtc(SDA, SCL);
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

// Push button

boolean oldSwitchState = LOW;
boolean newSwitchState = LOW;
boolean lcdScroll = LOW;
boolean lcdBacklight = LOW;
boolean lcdWelcome = LOW;

unsigned long previousMillis = 0;
const long BacklightTime = 10000;

void setup() {
  pinMode(Heater, OUTPUT);
  pinMode(Switch1, INPUT);
void loop() {
  float testTemp = sensors.getTempCByIndex(0);
  t = rtc.getTime();
  if(lcdWelcome == LOW){
      lcd.print("Welcome, Admin!");
      lcd.print("press Start");

  // LCD
  newSwitchState = digitalRead(Switch1);
    if (millis() - previousMillis >= BacklightTime) {
      lcdBacklight = LOW;
    else if ( lcdBacklight == LOW ){
      lcdBacklight = HIGH;
    if ( newSwitchState != oldSwitchState ) {
       if ( newSwitchState == HIGH ){
       previousMillis = millis();
       lcdWelcome = HIGH;
      if ( lcdScroll == LOW ){
        lcd.print("   ");
        lcdScroll = HIGH;
        lcd.print("   ");
        lcdScroll = LOW;
       oldSwitchState = newSwitchState;

How can i update the functions inside the if(lcdScroll == LOW){} and else{} statements constantly to show on display?

  • please use true and false as boolean values – Juraj Jun 17 '19 at 19:01
  • @Juraj thanks but does it make any difference? – ElectronSurf Jun 17 '19 at 19:07
  • 1
    I'm not clear on what your problem is - I don't see any blocking code here - you test the clock and the switches and either act on them or don't, which is appropriate. Also, what do you mean by "How to repeat an IF statement"? – JRobert Jun 17 '19 at 21:33
  • 1
    Also, do not compare values with true, false, 1, 0, or HIGH or LOW, just write if (variable), by default all nonzero values will result in executing the if statement. – Michel Keijzers Jun 17 '19 at 21:42
  • well your void loop() is already a while loop.....What is it that you are wanting to repeat that is not already happening? – Chad G Jun 17 '19 at 22:49

Like you suggested in your comment, you can implement a state machine, but the simplest would probably be setting a flag bool a_flag in this if(lcdScroll==LOW) clause and checking if(a_flag) in the highest scope of the loop() section. This is where you print("test");.

In respect to your code this will look like:

bool a_flag=false;
void loop() {
  // some irrelevant stuff
  if ( newSwitchState != oldSwitchState) {
    // some stuff
    if ( lcdScroll == LOW ){
      // stuff you would handle here
    else {
      // stuff you would handle here
  if (a_flag) Serial.println("lcdScroll is LOW");
  else Serial.println("lcdScroll is HIGH");

Beside this general solution you could simply do the following in your specific case:


  // your actual code

  if (lcdScroll) Serial.println("lcdScroll is LOW");
  else Serial.println("lcdScroll is HIGH");
| improve this answer | |
  • i'm very new to this can you please implant that in the code so i can get the whole idea? – ElectronSurf Jun 18 '19 at 9:02
  • @newbie You need to clear this flag somewhere and I'm not sure where (probably in the corresponding else{}). I'll add an implementation of this soon... – Sim Son Jun 18 '19 at 9:38
  • See my example implementation. This will continuously print the corresponding message. Note also that the backlight will behave erronuously when millis runs over! – Sim Son Jun 18 '19 at 12:22
  • i asked this question both in reddit and arduino forum and they didn't/couldn't give me an answer. you sir are a legend. thank you and god bless you. – ElectronSurf Jun 18 '19 at 14:29

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