LCD / Keypad Shield

We are building a thermostat to control our furnace and A/C. We are using a DFRobot LCD / Keypad shield we received from Hacktronics.com to display the temperature, and to set the temperature ranges for both the heating and cooling modes. The following is a sketch that shows how the lcd and the buttons are utilized. Only one analog input is needed for the 6 buttons, as they are connected to resistors, and the resistance is measured to determine which button is being pushed. We will be customizing this with a Dallas DS18B20 temperature sensor, and MOSFET / SSR control over the Furnace and A/C. A video of how this works has been uploaded to YouTube.

//Sample using LiquidCrystal library

#include "LiquidCrystal.h"

/*******************************************************

This program will test the LCD panel and the buttons

Mark Bramwell, July 2010

********************************************************/

// select the pins used on the LCD panel

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

// define some values used by the panel and buttons

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

// read the buttons

int read_LCD_buttons()

{

 adc_key_in = analogRead(0);      // read the value from the sensor

 // my buttons when read are centered at these valies: 0, 144, 329, 504, 741

 // we add approx 50 to those values and check to see if we are close

 if (adc_key_in > 1000) return btnNONE; // We make this the 1st option for speed reasons since it will be the most likely result

 if (adc_key_in < 50)   return btnRIGHT; 

 if (adc_key_in < 195)  return btnUP;

 if (adc_key_in < 380)  return btnDOWN;

 if (adc_key_in < 555)  return btnLEFT;

 if (adc_key_in < 790)  return btnSELECT;  

 return btnNONE;  // when all others fail, return this...

}

void setup()

{
 analogWrite(10, 50); // set brightness on pin 10 to 0-255

 lcd.begin(16, 2);              // start the library

 lcd.setCursor(0,0);

 lcd.print("Push the buttons"); // print a simple message

}

  

void loop()

{

 lcd.setCursor(9,1);            // move cursor to second line "1" and 9 spaces over

 lcd.print(millis()/1000);      // display seconds elapsed since power-up

 lcd.setCursor(0,1);            // move to the begining of the second line

 lcd_key = read_LCD_buttons();  // read the buttons

 switch (lcd_key)               // depending on which button was pushed, we perform an action

 {

   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;

     }

 }

}