Arduino lcd button input help

first you can not initialise two inputs with one statement

pinMode(buttonOne &&  buttonTwo, INPUT); will not work, you just tried to initialise button 0 (7 && 8) results in 0

you need to do this

pinMode(buttonOne, INPUT);

pinMode(buttonTwo, INPUT);

second you cant read two buttons at one with this kind of code, you can do it but using more advanced code, your not there yet

so you need

switchState = digitalRead(buttonOne);  
if (prevSwitchState != switchState){    
     if (buttonOne == HIGH){   
           lcd.print("B");    
     }  
}  
switchStateTwo = digitalRead(buttonTwo);  
if (prevSwitchStateTwo != switchStateTwo ){    
     if (buttonTwo== HIGH){   
           lcd.print("A");    
     }  
} 

this should fix your problem, note this is only correcting part of your program, you will need to fit it into your code

Regards

Peter

So in the end it should be like this?

#include LiquidCrystal

lcd(12, 11, 5, 4, 3, 2);

const int buttonOne = 8;

const int buttonTwo = 7;

int prevSwitchState = 0;

int switchState = 0;

int prevSwitchStateTwo = 0;

int switchStateTwo = 0;

void setup(){ 

lcd.begin(16, 2);

  pinMode(buttonOne, INPUT);

  pinMode(buttonTwo, INPUT);

lcd.print("Welcome"); 

lcd.setCursor(0,1);

lcd.print("Lftbtn = A");

  delay (5000);

  lcd.clear();//Clears screen

  lcd.print("Rgtbtn = B");

  delay (5000);

  lcd.clear();

}

void loop(){

  lcd.setCursor(0,0);

  switchState = digitalRead(buttonOne);

  if (prevSwitchState != switchState){       

  if (buttonOne == HIGH){      

     lcd.print("B");       

  }  

}   

switchStateTwo = digitalRead(buttonTwo);

   if (prevSwitchStateTwo != switchStateTwo ){   

      if (buttonTwo== HIGH){        

     lcd.print("A");       

  }  

}  

}

looks correct, have you tried it yet ?

looks correct, have you tried it yet ?

Ya I have tried it, but it still doesn't print the letters out. Maybe the buttons are broken?

Do you get the messages displayed on the LCD during the setup? (The welcome message etc) That would at least confirm the LCD and Arduino are both functional.

You can easily test if the buttons are broken by using either a resistance / continuity function on a multimeter, or failing that just take a line from the 5v on your Arduino, put an LED into a current limiting resistor and then the switch / button the other side of which connect to GND.

Have you pulled the pins 7 & 8 down to GND with a resistor (I usually go for 10K but most higher values would be ok)? This ensures the pin isn't floating and will read correctly when the switch is pushed.

The other thing that you could be giving you problems is switch bouncing. It looks like the code you have based you sketch on originally had some debouncing in it that hasn't quite made it across to your version. That is my assumption of the use of the prevSwitchState int as in your sketch it never changes and I can't really see a need for it.

There are a couple of different ways of debouncing a button if you believe that this is causing you a problem. Check out the Examples folder in the arduino IDE. In there you will see the Digital folder and inside a Debounce sketch which takes a reading from a button but doesn't act upon it for a few milliseconds when it can be sure that the switch has finished bouncing.

A good video to watch that might help you with tracking down some of these problems is the Tutorials for Arduino series by Jeremy Blum, specifically episode 2 where is sets up and input switch and walks though writing the code to debounce the input. https://www.youtube.com/watch?v=_LCCGFSMOr4

The setup messages are displayed and I have 10K resistors to ground, and the buttons seem to be working. I'll look up Jermey Blum's video.

You could test the continuity of the buttons pressed state with either the Ohms or continuity settings on a multimeter to test your buttons. Also your buttons could be in the wrong position, if you are using regular through hole tactile switches look and see which side the leads are coming out the two pins there are the correct ones to connect to your Arduino.

The continuity seems to be fine and the pins are the right way on the tactile switches

Are you able to test the pin voltage with a multimeter when the button is pressed? If it is reading correctly in both states then at least you'd know that it's now just a coding issue

Guys

The above code will never detect the second button as its outside of the main loop, and is not being called.

Try this to prove the switches work.

They should be connected to +5v and the pin, with the resistor from the pin to ground.

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int buttonOne = 8;
const int buttonTwo = 7;
int prevSwitchState = 0;
int switchState = 0;
int prevSwitchStateTwo = 0;
int switchStateTwo = 0;

void setup(){ 

lcd.begin(16, 2);
  pinMode(buttonOne, INPUT);
  pinMode(buttonTwo, INPUT);
lcd.print("Welcome"); 
lcd.setCursor(0,1);
lcd.print("Lftbtn = A");
  delay (5000);
  lcd.clear();//Clears screen
  lcd.print("Rgtbtn = B");
  delay (5000);
  lcd.clear();

}

void loop()
{
  lcd.setCursor(0,0);                //this is the top line at the far left position

  //switchState = digitalRead(buttonOne);

  //if (prevSwitchState != switchState){       

  if (digitalRead (buttonOne) == HIGH)
  {      
     lcd.print("B");       
  }  
    if (digitalRead (buttonTwo) == HIGH)
  {      
     lcd.print("A");       
  }
  

}   




// this will never run as its outside the loop. I commented it to compile.


//switchStateTwo = digitalRead(buttonTwo);

//   if (prevSwitchStateTwo != switchStateTwo ){   

//      if (buttonTwo== HIGH){        

//     lcd.print("A");       

//  }  

//}  

//}

If you get this far then you can worry about doing the other things.

Cheers

Mark

sorry mark, just tried what I had posted and it is in the loop, it is badly formatted so I re-aligned the braces below, both versions compile ok

peter

#include LiquidCrystal
lcd(12, 11, 5, 4, 3, 2);
const int buttonOne = 8;
const int buttonTwo = 7;
int prevSwitchState = 0;
int switchState = 0;
int prevSwitchStateTwo = 0;
int switchStateTwo = 0;
void setup(){ 
  lcd.begin(16, 2);
  pinMode(buttonOne, INPUT);
  pinMode(buttonTwo, INPUT);
  lcd.print("Welcome"); 
  lcd.setCursor(0,1);
  lcd.print("Lftbtn = A");
  delay (5000);
  lcd.clear();//Clears screen
  lcd.print("Rgtbtn = B");
  delay (5000);
  lcd.clear();
}
void loop()
{
   lcd.setCursor(0,0);
   switchState = digitalRead(buttonOne);
   if (prevSwitchState != switchState)
    {       
    if (buttonOne == HIGH)
      {      
         lcd.print("B");       
      }  
    }   
  switchStateTwo = digitalRead(buttonTwo);
  if (prevSwitchStateTwo != switchStateTwo )
   {   
      if (buttonTwo== HIGH)
      {        
         lcd.print("A");       
      }  
   }    
}