Need help with using millis() with lcd

zxames12 · March 5, 2022, 4:37am

Hi I am trying to use the function millis() with my lcd. What I want my code to do is display two sentences on the same line with a 3000 millis delay for each. However, I can not use the delay() function as I also have to use the keypad. With my code now when the cursor is at (0,2) the sentences keep overlapping and changing very quickly. Any suggestions on what I can add to my code to have that 3000 millis difference? Thank you.


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

LiquidCrystal_I2C lcd(0x27,20,4); 
#include <Keypad.h>

const long interval = 3000;
unsigned long currentMillis = 3000;

const byte ROWS = 4; 
const byte COLS = 4; 


char keys[ROWS][COLS] = {

  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte rowPins[ROWS] = { 9,8,7,6 };
byte colPins[COLS] = { 5,4,3,2 }; 

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); 


 long Num1,Num2,Number;
 char key,action;
 boolean result = false;
 
void setup() {
  lcd.init();  
  lcd.begin(20,4);                 
  lcd.backlight();  
}


void loop() {

  unsigned long currentMillis = millis();

  lcd.setCursor(0,2);             
  lcd.print("Dry Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("10");
  millis();
  lcd.print(" ");
 
  lcd.setCursor(0,2);             
  lcd.print("Wet Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("30");
  millis();
  lcd.print(" ");

  lcd.setCursor(0, 0);
  lcd.print("Enter Duct Size(in): ");
  
key = kpd.getKey(); 

if (key!=NO_KEY)
DetectButtons();

if (result==true)
CalculateResult();

DisplayResult();   
}


void DetectButtons()
{ 
    lcd.clear(); 
    if (key=='C') 
    {Serial.println ("Clear"); Number=Num1=Num2=0; result=false;}
    
    if (key == '1')
    {Serial.println ("Button 1"); 
    if (Number==0)
    Number=1;
    else
    Number = (Number*10) + 1; 
    }
    
     if (key == '4') 
    {Serial.println ("Button 4"); 
    if (Number==0)
    Number=4;
    else
    Number = (Number*10) + 4; 
    }
    
     if (key == '7') 
    {Serial.println ("Button 7");
    if (Number==0)
    Number=7;
    else
    Number = (Number*10) + 7; 
    } 
  

    if (key == '0')
    {Serial.println ("Button 0"); 
    if (Number==0)
    Number=0;
    else
    Number = (Number*10) + 0; 
    }
    
     if (key == '2') 
    {Serial.println ("Button 2"); 
     if (Number==0)
    Number=2;
    else
    Number = (Number*10) + 2; 
    }
    
     if (key == '5')
    {Serial.println ("Button 5"); 
     if (Number==0)
    Number=5;
    else
    Number = (Number*10) + 5; 
    }
    
     if (key == '8')
    {Serial.println ("Button 8"); 
     if (Number==0)
    Number=8;
    else
    Number = (Number*10) + 8; 
    }   
  

    if (key == '#')
    {Serial.println ("Equal"); 
    Num2=Number;
    result = true;
    }
    
     if (key == '3')
    {Serial.println ("Button 3"); 
     if (Number==0)
    Number=3;
    else
    Number = (Number*10) + 3; 
    }
    
     if (key == '6')
    {Serial.println ("Button 6"); 
    if (Number==0)
    Number=6;
    else
    Number = (Number*10) + 6; 
    }
    
     if (key == '9')
    {Serial.println ("Button 9");
    if (Number==0)
    Number=9;
    else
    Number = (Number*10) + 9; 
    }  

      if (key == '*') 
  {
    Num1 = Number;    
    Number =0;
    if (key == '*')
    {action = '*';}
    delay(100);
  }
  
}

void CalculateResult()
{
  if (action=='*')
    Number = Num1*Num2;
}

void DisplayResult()
{
  lcd.setCursor(2, 1);   
  lcd.print(Num1); lcd.print(action); lcd.print(Num2); 
  
  if (result==true)
  {lcd.print(" Area = "); lcd.print(Number/12); lcd.setCursor(17,1); lcd.print("ft");}

}

paulpaulson · March 5, 2022, 4:46am

Hello zxames12
Take a view at the BlinkWithOutDelay exmple from the IDE, based on this example you are able to design and build your own timers for your project.
Have a nice day and enjoy coding in C++.

zxames12 · March 5, 2022, 5:04am

Thank you for your help. I tried this but I am still getting the same result where the sentences are changing really fast. I would like the first sentence to change to the second one after 3000 millis. Is there anything else I can try?


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

LiquidCrystal_I2C lcd(0x27,20,4); 
#include <Keypad.h>

unsigned long previousMillis = 0;
const long interval = 3000;  

const byte ROWS = 4; 
const byte COLS = 4; 


char keys[ROWS][COLS] = {

  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte rowPins[ROWS] = { 9,8,7,6 };
byte colPins[COLS] = { 5,4,3,2 }; 

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); 


 long Num1,Num2,Number;
 char key,action;
 boolean result = false;
 
void setup() {
  lcd.init();  
  lcd.begin(20,4);                 
  lcd.backlight();  
}


void loop() {

  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
  }
  
  lcd.setCursor(0,2);             
  lcd.print("Dry Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("10");
  millis();
  lcd.print(" ");
 
  lcd.setCursor(0,2);             
  lcd.print("Wet Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("30");
  millis();
  lcd.print(" ");

  lcd.setCursor(0, 0);
  lcd.print("Enter Duct Size(in): ");
  
key = kpd.getKey(); 

if (key!=NO_KEY)
DetectButtons();

if (result==true)
CalculateResult();

DisplayResult();   
}


void DetectButtons()
{ 
    lcd.clear(); 
    if (key=='C') 
    {Serial.println ("Clear"); Number=Num1=Num2=0; result=false;}
    
    if (key == '1')
    {Serial.println ("Button 1"); 
    if (Number==0)
    Number=1;
    else
    Number = (Number*10) + 1; 
    }
    
     if (key == '4') 
    {Serial.println ("Button 4"); 
    if (Number==0)
    Number=4;
    else
    Number = (Number*10) + 4; 
    }
    
     if (key == '7') 
    {Serial.println ("Button 7");
    if (Number==0)
    Number=7;
    else
    Number = (Number*10) + 7; 
    } 
  

    if (key == '0')
    {Serial.println ("Button 0"); 
    if (Number==0)
    Number=0;
    else
    Number = (Number*10) + 0; 
    }
    
     if (key == '2') 
    {Serial.println ("Button 2"); 
     if (Number==0)
    Number=2;
    else
    Number = (Number*10) + 2; 
    }
    
     if (key == '5')
    {Serial.println ("Button 5"); 
     if (Number==0)
    Number=5;
    else
    Number = (Number*10) + 5; 
    }
    
     if (key == '8')
    {Serial.println ("Button 8"); 
     if (Number==0)
    Number=8;
    else
    Number = (Number*10) + 8; 
    }   
  

    if (key == '#')
    {Serial.println ("Equal"); 
    Num2=Number;
    result = true;
    }
    
     if (key == '3')
    {Serial.println ("Button 3"); 
     if (Number==0)
    Number=3;
    else
    Number = (Number*10) + 3; 
    }
    
     if (key == '6')
    {Serial.println ("Button 6"); 
    if (Number==0)
    Number=6;
    else
    Number = (Number*10) + 6; 
    }
    
     if (key == '9')
    {Serial.println ("Button 9");
    if (Number==0)
    Number=9;
    else
    Number = (Number*10) + 9; 
    }  

      if (key == '*') 
  {
    Num1 = Number;    
    Number =0;
    if (key == '*')
    {action = '*';}
    delay(100);
  }
  
}

void CalculateResult()
{
  if (action=='*')
    Number = Num1*Num2;
}

void DisplayResult()
{
  lcd.setCursor(2, 1);   
  lcd.print(Num1); lcd.print(action); lcd.print(Num2); 
  
  if (result==true)
  {lcd.print(" Area = "); lcd.print(Number/12); lcd.setCursor(17,1); lcd.print("ft");}

}

paulpaulson · March 5, 2022, 5:08am

Hello zxames12
Check your code again.
You have coded a timer but the timing function migth not be implemented correct.
Have a nice day and enjoy coding in C++.

zxames12 · March 5, 2022, 5:16am

Sorry can you show this on my code because I am having trouble understanding exactly what is wrong.

LarryD · March 5, 2022, 5:39am

Tell us what you think is happening here ?


  if (currentMillis - previousMillis >= interval) 
  {
    previousMillis = currentMillis;
  }

zxames12 · March 5, 2022, 5:48am

if the currentmillis - previousmillis is greater than or equal to the interval then they both equal each other?

LarryD · March 5, 2022, 5:57am

As it is, these lines of code don’t do anything useful.

If, on the other hand, you add some code between the braces, then that code would run every 3 seconds.

example:


interval = 3000;
. . .

  if (currentMillis - previousMillis >= interval) 
  {
    //restart this TIMER
    previousMillis = currentMillis;

    digitalWrite( myLED, !digitalRead(myLED);  // toggle myLED every 3 seconds
  }

zxames12 · March 5, 2022, 6:05am

Oh ok so if I were to add my lcd code between the braces then it should print every 3 seconds?

LarryD · March 5, 2022, 6:06am

Give it a try.

zxames12 · March 5, 2022, 6:29am

Thank you! I am getting closer to what I am wanting however, with this new change the lcd.print("Wet Bulb Temp ( C): "); line stays on the lcd and the lcd.print("Dry Bulb Temp ( C): "); line is going so fast I can't see it. I tried chaning the previousMillis = 0; and interval = 1000; values to a higher millis but the results are the same.


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

LiquidCrystal_I2C lcd(0x27,20,4); 
#include <Keypad.h>

unsigned long previousMillis = 0;
const long interval = 1000; 


const byte ROWS = 4; 
const byte COLS = 4; 


char keys[ROWS][COLS] = {

  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte rowPins[ROWS] = { 9,8,7,6 };
byte colPins[COLS] = { 5,4,3,2 }; 

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); 


 long Num1,Num2,Number;
 char key,action;
 boolean result = false;
 
void setup() {
  lcd.init();  
  lcd.begin(20,4);                 
  lcd.backlight();  
}


void loop() {

  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
  lcd.setCursor(0,2);             
  lcd.print("Dry Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("10");
  lcd.print(" ");
 
  lcd.setCursor(0,2);             
  lcd.print("Wet Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("30");
  lcd.print(" ");
    previousMillis = currentMillis;
  }
  

  lcd.setCursor(0, 0);
  lcd.print("Enter Duct Size(in): ");
  
key = kpd.getKey(); 

if (key!=NO_KEY)
DetectButtons();

if (result==true)
CalculateResult();

DisplayResult();   
}


void DetectButtons()
{ 
    lcd.clear(); 
    if (key=='C') 
    {Serial.println ("Clear"); Number=Num1=Num2=0; result=false;}
    
    if (key == '1')
    {Serial.println ("Button 1"); 
    if (Number==0)
    Number=1;
    else
    Number = (Number*10) + 1; 
    }
    
     if (key == '4') 
    {Serial.println ("Button 4"); 
    if (Number==0)
    Number=4;
    else
    Number = (Number*10) + 4; 
    }
    
     if (key == '7') 
    {Serial.println ("Button 7");
    if (Number==0)
    Number=7;
    else
    Number = (Number*10) + 7; 
    } 
  

    if (key == '0')
    {Serial.println ("Button 0"); 
    if (Number==0)
    Number=0;
    else
    Number = (Number*10) + 0; 
    }
    
     if (key == '2') 
    {Serial.println ("Button 2"); 
     if (Number==0)
    Number=2;
    else
    Number = (Number*10) + 2; 
    }
    
     if (key == '5')
    {Serial.println ("Button 5"); 
     if (Number==0)
    Number=5;
    else
    Number = (Number*10) + 5; 
    }
    
     if (key == '8')
    {Serial.println ("Button 8"); 
     if (Number==0)
    Number=8;
    else
    Number = (Number*10) + 8; 
    }   
  

    if (key == '#')
    {Serial.println ("Equal"); 
    Num2=Number;
    result = true;
    }
    
     if (key == '3')
    {Serial.println ("Button 3"); 
     if (Number==0)
    Number=3;
    else
    Number = (Number*10) + 3; 
    }
    
     if (key == '6')
    {Serial.println ("Button 6"); 
    if (Number==0)
    Number=6;
    else
    Number = (Number*10) + 6; 
    }
    
     if (key == '9')
    {Serial.println ("Button 9");
    if (Number==0)
    Number=9;
    else
    Number = (Number*10) + 9; 
    }  

      if (key == '*') 
  {
    Num1 = Number;    
    Number =0;
    if (key == '*')
    {action = '*';}
    delay(100);
  }
  
}

void CalculateResult()
{
  if (action=='*')
    Number = Num1*Num2;
}

void DisplayResult()
{
  lcd.setCursor(2, 1);   
  lcd.print(Num1); lcd.print(action); lcd.print(Num2); 
  
  if (result==true)
  {lcd.print(" Area = "); lcd.print(Number/12); lcd.setCursor(17,1); lcd.print("ft");}

}

LarryD · March 5, 2022, 6:40am

Since you are reusing the same LCD locations You need to come up with a design that switches between displays alternately.

Example:

Let’s say you have a variable called oddFlag

byte oddFlag = 0;

When oddFlag is == to 0 you print to the LCD Wet Bulb Temp
When oddFlag is == to 1 you print to the LCD Dry Bulb Temp

In your 3 second TIMER oddFlag needs to be changed between 0 and 1.
Therefore, the first 3 seconds you get Wet Bulb and then the next 3 seconds you get Dry Bulb etc.

zxames12 · March 5, 2022, 6:57am

Thank you that helped. How would i change oddFlag from 0 to 1 without manually typing it in?

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

LiquidCrystal_I2C lcd(0x27,20,4); 
#include <Keypad.h>

unsigned long previousMillis = 0;
const long interval = 100; 

byte oddFlag = 0;


const byte ROWS = 4; 
const byte COLS = 4; 


char keys[ROWS][COLS] = {

  {'1','2','3', 'A'},
  {'4','5','6', 'B'},
  {'7','8','9', 'C'},
  {'*','0','#', 'D'}
};

byte rowPins[ROWS] = { 9,8,7,6 };
byte colPins[COLS] = { 5,4,3,2 }; 

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS ); 


 long Num1,Num2,Number;
 char key,action;
 boolean result = false;
 
void setup() {
  lcd.init();  
  lcd.begin(20,4);                 
  lcd.backlight();  
}


void loop() {

  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {

  
  if (oddFlag==0)
    {
  lcd.setCursor(0,2);             
  lcd.print("Dry Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("10");
  lcd.print(" ");
  
    }  

  if (oddFlag==1)
  {
  lcd.setCursor(0,2);             
  lcd.print("Wet Bulb Temp ( C): ");
  lcd.setCursor(15,2);
  lcd.print((char)223);
  lcd.setCursor(1,3);
  lcd.print("20");
  lcd.print(" ");
  
  }
  previousMillis = currentMillis;
  }

LarryD · March 5, 2022, 7:21am

You need something like this (to be tested):

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

LiquidCrystal_I2C lcd(0x27, 20, 4);
#include <Keypad.h>

unsigned long previousMillis = 0;
const long interval = 100;

byte oddFlag    = 0;

const byte ROWS = 4;
const byte COLS = 4;


char keys[ROWS][COLS] =
{

  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[ROWS] = { 9, 8, 7, 6 };
byte colPins[COLS] = { 5, 4, 3, 2 };

Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );


long Num1, Num2, Number;
char key, action;
boolean result = false;


//***************************************************************************
void setup()
{
  lcd.init();
  lcd.begin(20, 4);
  lcd.backlight();
  
} //END of   setup()


//***************************************************************************
void loop()
{
  unsigned long currentMillis = millis();

  //**************************************************
  if (currentMillis - previousMillis >= interval)
  {
    //restart this TIMER
    previousMillis = currentMillis;

    //**********************
    if (oddFlag == 0)
    {
      lcd.setCursor(0, 2);
      lcd.print("Dry Bulb Temp ( C): ");
      lcd.setCursor(15, 2);
      lcd.print((char)223);
      lcd.setCursor(1, 3);
      lcd.print("10");
      lcd.print(" ");
    }

    //**********************
    else
    {
      lcd.setCursor(0, 2);
      lcd.print("Wet Bulb Temp ( C): ");
      lcd.setCursor(15, 2);
      lcd.print((char)223);
      lcd.setCursor(1, 3);
      lcd.print("20");
      lcd.print(" ");
    }

    //toggle the Flag
    oddFlag = 1 - oddFlag;

  }

} //END of   loop()

zxames12 · March 5, 2022, 7:26am

That worked!! Thank you so much!

LarryD · March 5, 2022, 7:26am

You need to make interval = 3000; //3 seconds

Do you know why it works ?

zxames12 · March 5, 2022, 7:27am

Yes i changed it to 3000. Thank you again!

LarryD · March 5, 2022, 7:27am

Do you know why it works ?

zxames12 · March 5, 2022, 7:28am

yes I had to make it an if else statement to have the print change.

LarryD · March 5, 2022, 7:29am

And you have to:

    //toggle the Flag
    oddFlag = 1 - oddFlag;

When it is 0, it changes to 1 (Odd)

When it is 1, it changes to 0 (Even)

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