How do I control the buttons on an Arduino LCD keypad shield?

Question

I have just bought a 16x2 LCD display with buttons. I can get the display to work and do various basic sketches included in the Arduino IDE. However, I cannot figure out how to control the buttons.

The buttons work using analog pin 0 and from what I was able to understand from what I have read online, it is something to do with the values you receive when the buttons are pressed. I can't seem to find out what values mine gives, I have found a sketch that is supposed to map the buttons, but I cannot get it to work, as I don't really understand what it is doing, I am very new to this.

The code I am using is as follows:

#include <LiquidCrystal.h>

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

int lcd_key     = 0;
int adc_key_in  = 0;

#define btnRIGHT  0
#define btnUP     1
#define btnDOWN   2
#define btnLEFT   3
#define btnSELECT 4
#define btnNONE   5

int read_LCD_buttons() {
  adc_key_in = analogRead(0);
  if (adc_key_in > 1000) return btnNONE;
  if (adc_key_in < 50)   return btnRIGHT;
  if (adc_key_in < 250)  return btnUP;
  if (adc_key_in < 450)  return btnDOWN;
  if (adc_key_in < 600)  return btnLEFT;
  if (adc_key_in < 920)  return btnSELECT;
  return btnNONE;
}

void setup() {
  lcd.begin(16, 2);
  lcd.setCursor(0,0);
  lcd.print("Push the buttons");
}

void loop() {
  lcd.setCursor(9, 1);
  lcd.print(millis()/1000);
  lcd.setCursor(0, 1);
  lcd_key = read_LCD_buttons();
  switch (lcd_key) {
    case btnRIGHT: {
      lcd.print("RIGHT ");
      break;
    }
    case btnLEFT: {
      lcd.print("LEFT   ");
      break;
    }
    case btnUP: {
      lcd.print("UP    ");
      break;
    }
    case btnDOWN: {
      lcd.print("DOWN  ");
      break;
    }
    case btnSELECT: {
      lcd.print("SELECT");
      break;
    }
    case btnNONE: {
      lcd.print("NONE  ");
      break;
    }
  }
}

If anyone can give me any pointers it would be greatly appreciated.

Liam

Answer 1

I have found an easy way to do this, i found a tutorial on instructables that has explained in detail what to do, i then applied this to my LCD keypad shield rather than external buttons on a breadboard.

All you have to do to see what the results are for your particular buttons is to load the sketch below onto your board then open the serial mapper on the arduino ide, simply press the buttons and you should see the results.

 /* 
  Debounce

  Each time the input pin goes from LOW to HIGH (e.g. because of a push-button
  press), the output pin is toggled from LOW to HIGH or HIGH to LOW.  There's
  a minimum delay between toggles to debounce the circuit (i.e. to ignore
  noise).  

  created 28 October 2009
  by Riaan Cornelius


  */

 // constants won't change. They're used here to 
 // set pin numbers:
 const int buttonPin = 0;     // the number of the pushbutton pin
 const int ledPin =  53;      // the number of the LED pin for testing

 const int BUTTON1 = 1;
 const int BUTTON2 = 2;
 const int BUTTON3 = 3;
 const int BUTTON4 = 4;
 const int BUTTON5 = 5;

 const int BUTTON1LOW = 970;
 const int BUTTON1HIGH = 1024;
 const int BUTTON2LOW = 850;
 const int BUTTON2HIGH = 950;
 const int BUTTON3LOW = 700;
 const int BUTTON3HIGH = 800;
 const int BUTTON4LOW = 400;
 const int BUTTON4HIGH = 650;
 const int BUTTON5LOW = 250;
 const int BUTTON5HIGH = 350;

 // Variables will change:
 int ledState = HIGH;         // the current state of the output pin
 int buttonState;             // the current reading from the input pin
 int lastButtonState = LOW;   // the previous reading from the input pin

 // the following variables are long's because the time, measured in miliseconds,
 // will quickly become a bigger number than can be stored in an int.
 long lastDebounceTime = 0;  // the last time the output pin was toggled
 long debounceDelay = 50;    // the debounce time; increase if the output flickers

 void setup() {
   pinMode(buttonPin, INPUT);
   pinMode(ledPin, OUTPUT);
   Serial.begin(9600);
 }

 void loop() {
   // read the state of the switch into a local variable:
   int reading = analogRead(buttonPin);
   Serial.println(reading);

   /*
   Not needed while getting the values.

   int tmpButtonState = LOW;             // the current reading from the input pin

   if(reading>BUTTON5LOW && reading<BUTTON5HIGH){
     //Read switch 5
     tmpButtonState = BUTTON5;
   }else if(reading>BUTTON4LOW && reading<BUTTON4HIGH){
     //Read switch 4
     tmpButtonState = BUTTON4;
   }else if(reading>BUTTON3LOW && reading<BUTTON3HIGH){
     //Read switch 3
     tmpButtonState = BUTTON3;
   }else if(reading>BUTTON2LOW && reading<BUTTON2HIGH){
     //Read switch 2
     tmpButtonState = BUTTON2;
   }else if(reading>BUTTON1LOW && reading<BUTTON1HIGH){
     //Read switch 1
     tmpButtonState = BUTTON1;
   }else{
     //No button is pressed;
     tmpButtonState = LOW;
   }

   // check to see if you just pressed the button 
   // (i.e. the input went from LOW to a buttonState),  and you've waited 
   // long enough since the last press to ignore any noise:  

   // If the switch changed, due to noise or pressing:
   if (tmpButtonState != lastButtonState) {
     // reset the debouncing timer
     lastDebounceTime = millis();
   } 

   if ((millis() - lastDebounceTime) > debounceDelay) {
     // whatever the reading is at, it's been there for longer
     // than the debounce delay, so take it as the actual current state:
     buttonState = tmpButtonState;
     Serial.println(buttonState);
   }

   // save the reading.  Next time through the loop,
   // it'll be the lastButtonState:
   lastButtonState = tmpButtonState;

   // set the LED using the state of the button for testing:
   switch(buttonState){
     case BUTTON1:
     digitalWrite(ledPin, buttonState>0);
     break;
     case BUTTON2:
     digitalWrite(ledPin, buttonState>0);
     break;
     case BUTTON3:
     digitalWrite(ledPin, buttonState>0);
     break;
     case BUTTON4:
     digitalWrite(ledPin, buttonState>0);
     break;
     case BUTTON5:
     digitalWrite(ledPin, buttonState>0);
     break;
   }
   */
 }

Liam