tachtometer lcd

Using Arduino Programming Questions
#1

hey guys im trying to make a lcd tachtometer and im using this as example :

only thing that is diffrent is the arduino i use (arduino ragepip) and a diffrent sensor. the problem i have right now is that the lcd is only showing some blocks and no numbers or words i hopethat somone is able to help me.

p.s sorry for the bad english

here is the code im using

#include<LiquidCrystal.h>
LiquidCrystal lcd(12,11,6,5,4,3);
int pwm=9;
int pot=A0;
float value=0;
int percent;
float rev=0;
int rpm;
int oldtime=0;
int time;

void isr() //interrupt service routine
{
rev++;
}

void setup()
{
lcd.begin(16,2); //initialize LCD
attachInterrupt(0,isr,RISING); //attaching the interrupt
}

void loop()
{
delay(1000);
detachInterrupt(0); //detaches the interrupt
time=millis()-oldtime; //finds the time
rpm=(rev/time)*60000; //calculates rpm
oldtime=millis(); //saves the current time
rev=0;
value=analogRead(pot); //reads the speed control POT
value=value/4;
analogWrite(pwm,value); //sets the desired speed
percent=(value/255)*100; //finds the duty cycle %
lcd.clear();
lcd.setCursor(0,0);
lcd.setCursor(0,1);
lcd.print(“TACHOMETER”);
lcd.print(rpm);
lcd.print(" RPM");
lcd.print(" “);
lcd.print(percent);
lcd.print(”%");
attachInterrupt(0,isr,RISING);

#2

UnoWatt:
Have you tried a simple sketch with nothing in except getting the LCD to do "Hello, world?"

yes i did i only get more shorter blocks hehehe....
edit:

for some reason it only shows 'hello w and then x amount of seconds

#3

Variables used in an interrupt service routine and in other functions, like rev, need to be declared volatile.

Rather than detaching the interrupt handler, and reattaching it, you should be using noInterrupts() and interupts() around the code that copies the data in the interrupt-set variable(s).

Using millis() and delay() in the same code indicates that not enough thought went into writing the code. There is NO reason to be using delay() at all.

#4