Trouble with buttons (Arduino) - arduino

Question

StackOverflow! I am a teenager fairly new to Arduino coding, and am investigating a problem. I am running Linux Ubuntu 10.10 if that makes a difference. I have a setup going with a homemade board consisting of five buttons, one for each left, right, up, and down, and one center button, and a Hitachi 2x16 character LCD screen, using the Arduino Uno board.. My programs purpose is to play my splash screen, issue a countdown from three on-screen, display a helpful message, and then go into the program, which simply opens up a list of items, showing one at a time, and allows you to scroll through them using the up and down buttons, and exit the program by clicking the center button. So, here's the problem: the rest of the program works just fine, but when it comes to the menu, it correctly displays the first item, but the buttons do not serve their purpose. I checked using the serial monitor, and the state of the button doesn't change when pressed. But here's the kicker. I used a volt meter to check if the buttons were correctly using power, and they are. They just don't seem to be working digitally. I have checked my wiring, and it is all correct. I think the problem may be in the code, so I leave it to your more experienced hands:
// include the library code:
#include <LiquidCrystal.h>
int itemNum = 0;
// Declare variables for on and off states, for efficiency!
int on = LOW;
int off = HIGH;
// Declare the buttons' digital pins and states respectively
const int upbtnpin = 8;
const int dwnbtnpin = 9;
const int cntrbtnpin = 10;
int upbtnstate = off;
int dwnbtnstate = off;
int cntrbtnstate = off;
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup() {
// Activate Serial Monitor
Serial.begin(9600);
// Declare buttons to be INPUT
pinMode(upbtnpin, INPUT);
pinMode(dwnbtnpin, INPUT);
pinMode(cntrbtnpin, INPUT);
// Activate Pullups
digitalWrite(upbtnpin, HIGH);
digitalWrite(dwnbtnpin, HIGH);
digitalWrite(cntrbtnpin, HIGH);
// Begin LCD
lcd.begin(16, 2);
// Splash Screen
lcd.setCursor(0, 0);
lcd.print(" _# Paradigm #_");
lcd.setCursor(0,1);
lcd.print("<-> Robotics <->");
delay(3000);
lcd.clear();
// Display Message and countdown
cntrbtnstate = digitalRead(cntrbtnpin);
lcd.setCursor(0, 0);
lcd.print("Menu Program 1.0");
lcd.setCursor(0, 1);
int i = 3;
while (i > 0) {
if (i == 3) {
lcd.setCursor(0, 1);
lcd.print("Wait 3 second(s)");
delay(1000);
i--;
}
else if (i == 2) {
lcd.setCursor(0, 1);
lcd.print("Wait 2 second(s)");
delay(1000);
i--;
}
else if (i == 1) {
lcd.setCursor(0, 1);
lcd.print("Wait 1 second(s)");
delay(1000);
i--;
}
}
lcd.clear();
delay(500);
lcd.setCursor(0, 0);
lcd.print("Press enter any");
lcd.setCursor(0, 1);
lcd.print(" time to exit. ");
delay(1200);
lcd.clear();
}
// ...And finally, to the actual program!
void loop() {
upbtnstate = digitalRead(upbtnpin);
dwnbtnstate = digitalRead(dwnbtnpin);
cntrbtnstate = digitalRead(cntrbtnpin);
while (cntrbtnstate != on) {
if (upbtnstate == on) {
delay(250);
itemNum++;
}
else if (dwnbtnstate == on) {
delay(250);
itemNum--;
}
// OPTIONAL for debugging
delay(150);
Serial.print(" ! ");
delay(150);
Serial.print(int(upbtnstate));
Serial.print(" ");
delay(150);
Serial.print(int(dwnbtnstate));
Serial.print(" ");
delay(150);
Serial.print(int(cntrbtnstate));
String item = "";
int itemNum = 0;
switch(itemNum) {
case 0:
lcd.setCursor(0, 1);
lcd.print("END OF LIST");
break;
case 1:
lcd.setCursor(0, 1);
lcd.print("Water Bottle");
break;
case 2:
lcd.setCursor(0, 1);
lcd.print("Biker Jacket");
break;
case 3:
lcd.setCursor(0, 1);
lcd.print(".44 Magnum");
break;
case 4:
lcd.setCursor(0, 1);
lcd.print(".44 Rounds (x14)");
break;
case 5:
lcd.setCursor(0, 1);
lcd.print("Machete");
break;
case 6:
lcd.setCursor(0, 1);
lcd.print("END OF LIST");
break;
default:
lcd.setCursor(0, 0);
lcd.print(" An error has ");
lcd.setCursor(0, 1);
lcd.print(" occoured ");
}
if (itemNum > 6) {
itemNum == 6;
}
else if (itemNum < 0) {
itemNum == 0;
}
lcd.setCursor(0, 1);
lcd.print(item);
}
lcd.clear();
lcd.setCursor(0, 1);
lcd.print(" Goodbye! ");
}

Answer 1

First, you need to de-bounce the buttons.
http://arduino.cc/it/Tutorial/Debounce
Second, immediately before your case statement, you set the itemNum to 0. That should probably be moved to the setup section, otherwise it will reset the itemNum each iteration of the loop, and you will always be stuck on "END OF LIST".
Likewise with String item = ""; You are blanking out the string each iteration of the loop, and it runs faster than you can press the buttons.
Also, I don't see any code that ever sets the String item to anything except "". Since you print the item name in the case statement, perhaps you can just remove "String item" and all references.
Finally, you can shorten the delay loop section to :
int i = 3;
while (i > 0) {
lcd.setCursor(0, 1);
lcd.print("Wait " + i + " second(s)");
delay(1000);
i--;
}