store when the button is pressed

Using Arduino Programming Questions
#1

hello , i need to register the time each button (there are 2 buttons ) has pressed to compare the difference ,
the time of the press of button1 - the time of the pree of button2
or vise versa should be less than 50ms to light up a redled
here what i tried to code but its not working fine , please help!

int button =3;
int button2 =4;
int redled =5;

void setup () {
pinMode(button,INPUT);
pinMode(button2,INPUT);
pinMode(redled,OUTPUT);
}

void loop () {
unsigned long firstpress;
unsigned long secondpress;

if (digitalRead(button)==HIGH) {
firstpress = millis();
}
if (digitalRead(button2)==HIGH) {
secondpress = millis();
}
if (firstpress - secondpress <= 50) {
digitalWrite(redled,HIGH);
delay(2000);
}
firstpress = digitalRead(button);
secondpress = digitalRead(button2);
}
#2

this

if (firstpress - secondpress <= 50) {

should be

if (secondpress - firstpress <= 50) {

no?

50ms seems awfully short though.

#3

How many times do you suppose loop() will iterate before both switches are pressed? Does creating a new variable on each pass make sense? To me, it does not.

Make the times static or global so that doesn't happen.

#4

so this should work ?

int button =3;
int button2 =4;
int redled =5;
unsigned long firstpress;
unsigned long secondpress;

void setup () {
pinMode(button,INPUT);
pinMode(button2,INPUT);
pinMode(redled,OUTPUT);
}

void loop () {


if (digitalRead(button)==HIGH) {
firstpress = millis();
}
if (digitalRead(button2)==HIGH) {
secondpress = millis();
}
if (secondpress-firstpress <= 50) {
digitalWrite(redled,HIGH);
delay(2000);
}
firstpress = digitalRead(button);
secondpress = digitalRead(button2);
}
#5

hossamsh:
so this should work ?

int button =3;

int button2 =4;
int redled =5;
unsigned long firstpress;
unsigned long secondpress;

void setup () {
pinMode(button,INPUT);
pinMode(button2,INPUT);
pinMode(redled,OUTPUT);
}

void loop () {

if (digitalRead(button)==HIGH) {
firstpress = millis();
}
if (digitalRead(button2)==HIGH) {
secondpress = millis();
}
if (secondpress-firstpress <= 50) {
digitalWrite(redled,HIGH);
delay(2000);
}
firstpress = digitalRead(button);
secondpress = digitalRead(button2);
}

try it and tell us what happens

#6

so this should work ?

No. You want to record when the switch BECOMES pressed, not when the switch IS pressed.

I'm getting really tired of telling people to look at the state change detection example.

#7

No, there's a fundamental problem here - you are not detecting when the button is pressed.

The button is pressed at the point where it now reads HIGH but last time it read LOW - you have
to save the state of the last time you called digitalRead() and compare against the new reading.

Have a look at StateChangeDetection example (I think that's the name) in the Arduino examples.

#8

Well, it would still work even though he is level sensing instead of edge-sensing. He has 2 buttons.

It just wouldn't work exactly the way it should.

#9