[LCD without delay]

Projects Programming
1

Hi there :), I am using an Arduino Uno R3, with an I2C LCD module connected to an LCD.

I want to display a message on my LCD without using a delay. I want to achieve this using the millis() function.

It works fine with delay() but with millis(), the LCD never displays the 2th message in the loop. So, the if-condition is never met. It seems like I am doing something wrong here. I appreciate your aid.

My research:

https://forum.arduino.cc/index.php?topic=58687.0

Arduino Electrical Diagram:

Arduino I2C LCD Electrical Diagram.png
Arduino I2C LCD Electrical Diagram.png753×801 45.4 KB

My code:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

String gamemodeMessage;

unsigned long previousTime = 0;
long interval;

void setup() {
  lcd.backlight();
  lcd.begin();
  lcd.clear();
  lcd.print("Active Learning");
  lcd.setCursor(0, 1);
  lcd.print("Welcome!");
  delay(1000);
}

void gamemodeControl() {
  unsigned long currentTime = millis();
  interval = 1000;

  gamemodeMessage = "+";
  if ((currentTime - previousTime >= interval) && (millis() - previousTime < (interval * 2))) {
    lcd.setCursor(0, 0);
    lcd.clear();
    lcd.print("Gamemode:");
    lcd.setCursor(11, 0);
    lcd.print("");
    lcd.setCursor(0, 1);
    lcd.print(gamemodeMessage);
  }

  else if (millis() - previousTime > (interval * 2)) {
    interval = millis();
  }
}

void loop() {
  gamemodeControl();
  gamemodeMessage = "gamemode 1"; //testing purpose
  delay(50);
  gamemodeMessage = "gamemode 2";
  delay(50);
  gamemodeMessage = "gamemode 3";
  delay(50);
}

Arduino I2C LCD Electrical Diagram.png
Arduino I2C LCD Electrical Diagram.png753×801 45.4 KB

2

Think about that for a minute or two interval = millis();

3

Thank you for your reply, I found one problem.

J-M-L:
Think about that for a minute or two interval = millis();

My Serial Monitor shows the interval value being increased by 1000 each time. So every time the loop cycles, the LCD has to wait 1 second longer, until it becomes 50 days long and overflows. So, this isn't the right way.

I disabledinterval = millis();

So, now the problem is still that the if-condition is never met. There is still a problem there.

4

What’s the purpose of previousTime?

5

PreviousTime is compared with the CurrentTime. If the difference is greater than the interval. Then the lCD code will execute.

6

So once it’s triggered, what should previousTime become?
(There is a good tutorial on how to use millis() pinned at the top of the forum. Suggest you read it :slight_smile: )

7

I appreciate your quick responses. :slight_smile: The previousTime should save the value of the currentTime when the value difference becomes greater than the interval.

My purpose is to implement this with a sensor in the future. Certain values have a unique gamemode assigned to them. Now, the problem is that the gamemode String message doesn't update. A solution would be to call gamemodeMessage() again after the message string updates, but that causes screen flicker again and it would defeat my purpose of using the millis() function. I would have to add a delay() again.

Possible solution?
-Switch cases with breaks

Are there more practical ways to solve this problem?

I changed my code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int liveAmount = 3;
String gamemodeMessage;

unsigned long previousTime = 0;
unsigned long interval = 1000;

void setup() {
  Serial.begin(9600);
  lcd.backlight();
  lcd.begin();
  lcd.clear();
  lcd.print("Active Learning");
  lcd.setCursor(0, 1);
  lcd.print("Welcome!");
  delay(1000);
}

void gamemodeControl() {
  unsigned long currentTime = millis();

  if (currentTime - previousTime >= interval) {
    lcd.setCursor(0, 0);
    lcd.clear();
    lcd.print("Gamemode:");
    lcd.setCursor(11, 0);
    lcd.print("");
    lcd.setCursor(0, 1);
    lcd.print(gamemodeMessage);
    previousTime = currentTime;
  }
}

void loop() {
  gamemodeControl();
  gamemodeMessage = "gamemode 1"; //testing purpose
  Serial.println(gamemodeMessage);
  gamemodeMessage = "gamemode 2";
  Serial.println(gamemodeMessage);
  gamemodeMessage = "gamemode 3";
  Serial.println(gamemodeMessage);
}
8

You should referesh only the part Of the LCD that needs refresh, when its content has changed... that’s the best way to avoid flickering :slight_smile:

(And yes for previousTime)

9

I modified the code to work with sensors. I didn't know you could refresh only a certain part of the LCD. I will have to look into that later. I am happy with this code. I works fine for now :).

Resetting

lcd.setCursor(x, y);
lcd.print(" ");

My code

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int liveAmount = 3;
int var;
String gamemodeMessage = "None Selected";

unsigned long previousTime = 0;
unsigned long interval = 1000;

void setup() {
  Serial.begin(9600);
  lcd.backlight();
  lcd.begin();
  lcd.clear();
  lcd.print("Active Learning");
  lcd.setCursor(0, 1);
  lcd.print("Welcome!");
  delay(1000);
}

void gamemodeControl() {
  unsigned long currentTime = millis();

  if (currentTime - previousTime >= interval) {
    lcd.setCursor(0, 0);
    lcd.clear();
    lcd.print("Gamemode:");
    lcd.setCursor(11, 0);
    lcd.print("");
    lcd.setCursor(0, 1);
    lcd.print(gamemodeMessage);
    previousTime = currentTime;
  }
}

void loop() {
  gamemodeControl();
  var = 1; //testing purpose
  //var = 2;
  //var = 3;
  switch (var) {
    case 1:
      gamemodeMessage = "gamemode 1"; 
      Serial.println(gamemodeMessage);
      break;
    case 2:
      gamemodeMessage = "gamemode 2"; 
      Serial.println(gamemodeMessage);
      break;
    case 3:
      gamemodeMessage = "gamemode 3"; 
      Serial.println(gamemodeMessage);
      break;
  }
}