Hi,
I have very simple problem, but I cant find the right simple solution. Please can anyone help me?
:
I have a button sensor that indicates if it is HIGH or LOW. What I need is to light up the LED when I press the button for the first time, keep the LED shining when I hold the button and also keep it on when move finger away and the sensor input indicates LOW.
Than when I press the button once again the led might turn out.
So it should work like ON/OFF button. Press once and keep the LED shining all the time and than press once again and LED stop shining - indicates OFF.
void loop()
{
while (digitalRead(BUTTONPIN) == HIGH); // wait until button is pressed
ledState = ledState == HIGH ? LOW : HIGH; // change LED state
digitalWrite(LEDPIN, ledState); // set LED to new state
while (digitalRead(BUTTONPIN) == LOW); // wait until button is released
}
(This assumes that the button brings the pin low; if not, simply reverse the while loops.)
unfortunatelly it doesnot work...
what is this part of code:
ledState = ledState == HIGH ? LOW : HIGH; // change LED state
its really strange for me and I dont understand it...
void loop()
{
if ( BUTTONPIN==HIGH && X==0)
{
digitalWrite(LED, HIGH);
delay(1000);
X += 1; // X is variable that might
detect, if the button was
pressed before or not
BUT here I want to add
just 1 / not more... I
dont know how. What
happens with multiple additions +1 when I use constrain(X,0,1) in the begining of code???
}
if ( BUTTONPIN== LOW && X==1)
{
digitalWrite (LED, HIGH);
}
if ( BUTTONPIN==HIGH && X==1)
{
digitalWrite (LED, LOW);
delay(1000);
X -= 1;
}
if (BUTTONPIN==LOW && X==0)
{
digitalWrite (LED,LOW);
}
}
Thanks for any idea for improving or rebuilding...
Mikal's expression toggles the value of ledState using the C ternary operator. It looks strange at first but is quite useful writing if/then/else statements.
The expression above is the same as the following:
if(ledState == HIGH)
ledState = LOW; // set the state LOW if it was HIGH
else
ledState = HIGH; // state was LOW set set it HIGH
here is how the ternary operator works:
result = ledState == HIGH [glow]?[/glow] LOW [glow]:[/glow] HIGH
\_____________/ | |
| | \- result will be this if ledState was LOW
| \ - result will be this if ledState was HIGH
|
\ - this expression is evaluated, the result will be the value
after the [glow]?[/glow] if true, or after the [glow]:[/glow] if false
boolean bCurrentlyOn = false;
void setup(void){/*your code*/}
void loop(void)
{
if(digitalRead(BUTTONPIN)==LOW && bCurrentlyOn)
{
digitalWrite(LEDPIN,LOW);
bCurrentlyOn=false;
delay(10);//do not know if needed, but I think it is or else the next if block will execute
}
else if(digitalRead(BUTTONPIN)==LOW && !bCurrentlyOn)
{
digitalWrite(LEDPIN,HIGH);
bCurrentlyOn=true;
delay(10);//do not know if needed, but I think it is or else the next if block will execute
}
}
The delay is needed to debounce the switch.
When you press a button the contact opens and closes rapidly for a short period (10 to 20 milliseconds) so you should wait for the contact to stop bouncing before leaving the if statement
I am using an old footswitch to switch a laser on and off and mikalhart's solution is very nice.
The scripts main part sends midi controller values and I dont want that to stutter by
adding delay but the footswitch "spills" a lot. So I need the switch state to be less sensitive,
maybe using millis?
If you can re-wire the switch, then you can de-bounce it it hardware using the standard circuit with a set-reset latch. Is re-wiring the switch a possibility in this case?
