With interrupts, you can be sure you won’t miss it. Example 04: Multiple states from a single push button switch, Polling. }. If you wished you could check LEDstatus, // if the blinking LED is on. if (state > 3) { state = 0; } Find this and other Arduino tutorials on ArduinoGetStarted.com. Serial.print("Sketch: "); Serial.println(__FILE__); Two new variables have been added; oldSwitchState and newSwitchState. unsigned long timeLastKeyPress = 0; boolean newSwitchState1 = LOW; – state = 1 – green LED on As mentioned above, there are 4 types of interrupt and you specify which one you want to use by using one of 4 system variables; LOW, CHANGE, RISING, or, FALLING. else This is a good thing, but here we need to tell it to “slow down” on optimization. boolean keyPressed = false; boolean newSwitchState = LOW; // For us humans, this means turning on notifications. if (state==3) { digitalWrite(pin_LEDred, HIGH); }. // variables to hold the times if (timeNow-timePrev >= timeWait ) // timeNow = millis(); timePrev = timeNow; I modified it further like this after reading the comment you made bellow the code example and it still appears to work the same. oldSwitchState = newSwitchState1; digitalWrite(pin_LED,LOW); Hence the name switch bounce. {, // has the button switch been closed? // D2 to push button switch digitalWrite(pin_LED,LOW); pinMode(pin_LED1, OUTPUT); delay(1); Excellent guide. boolean newSwitchState2 = LOW; digitalWrite(pin_led, LOW); Serial.println(" "); if (state==2) { digitalWrite(pin_LEDyellow, HIGH); } if ( newSwitchState1 == HIGH ) Excellent guide!!!!! { New variables have been introduced to hold the times and the rate of blink (timeWait). flashingLEDisON = true; pinMode(pin_switch, INPUT); For example, I use similar techniques when setting up remote controls using Bluetooth and wifi connections and instead of setting a pin state I send control codes. // position 0 is not used (considered not good practice but keeps the code easy to understand), // An example of using a button switch as a toggle switch to turn a blinking LED on or off, // the LED may be on so to be safe we turn it off. The monitoring for Arduino Interrupts is done by hardware, not software. if ( keyPressed ) else // Now using an array to store the LED pins AVR based Arduino's do not support (hardware) threading, I am unfamiliar with the ARM based Arduino's. Polling is like checking the front door every minute or so to see if the postman is delivering your new Arduino. digitalWrite(pin_led, LOW); void loop() { Example 02: Turning an LED on and off with debounce I have no room for any code my sketch is driving a led matrix and simulating a flickering flame. We initialize the pin of the LED as OUTPUT and the pin of the button as INPUT. My project is a light to help people with photo-phobia or an extra sensitivity to light. LOW – the interrupt is triggered whenever the pin is LOW if ( (newSwitchState1==newSwitchState2) && (newSwitchState1==newSwitchState3) ) { { Second option – interrupts – you put a note on your door saying “Dear Mr. Postman, please ring the bell when you see this”. Serial.println(" "); newSwitchState = digitalRead(pin_switch); // If you need more pins here you can find the pcf8575 16bit version of the IC. int pin_LED = 10; We then use the LED sequence array with the state variable as the index value to turn on the next LED. digitalWrite(LED_Sequence_array[state],HIGH); Another example: you’re waiting to talk to the postman about something. if (keyPressed) // I have added 2 new LEDs to pins 9 and 8. if ( keyPressed ) To get around this the Arduino developers introduced the system variable digitalPinToInterrupt(pin) and on the Nano, digitalPinToInterrupt(2) = 0 and digitalPinToInterrupt(3) = 1. That’s why it’s called an interruption. } We can either use pin 2 or pin 3. There are many solutions to turning an LED on and off and a lot depends on how you want your sketch to work, how quickly you need the Arduino to react and what interface you want to use; one button switch, two button switches, a key pad, etc. newSwitchState = digitalRead(pin_switch); Once you can create the code to blink an LED you can create code to turn anything on and off. boolean newSwitchState2 = LOW; pinMode(pin_LEDgreen, OUTPUT); digitalWrite(pin_LEDgreen,LOW); Pay attention when you have to choose a pin for an interrupt. Pingback: What Arduino Kit Should I buy? { oldSwitchState = newSwitchState; pinMode(pin_LEDyellow, OUTPUT); digitalWrite(pin_LEDyellow,LOW); { } newSwitchState2 = digitalRead(pin_switch); delay(1); } newSwitchState2 = digitalRead(pin_switch); // has the button switch been closed? int pin_switch = 2; pinMode(pin_LED, OUTPUT); On the 4th press the LEDs reset to all off. What is an Interrupt? // Pins Switching things: Polling examples (1 to 5a). if ( flashingLEDisON == false) For that you’ll have to modify the 3rd parameter of the attachInterrupt() function: Practically speaking, you could monitor when the user presses the buttons, or when he/she releases the button, or both. From the variable names it should be obvious what the pins are used for. Delay() should not be used (it uses interrupts so doesn’t work inside an ISR), millis() will not work and serial print doesn’t work correctly. So for param1, we would use 0 for pin D2 and 1 for pin D3. Do you want to become better at programming robots, with Arduino, Raspberry Pi, or ROS2? if ( (newSwitchState1==newSwitchState2) && (newSwitchState1==newSwitchState3) ) unsigned long timeNow = 0; // void loop() pinMode(pin_switch, INPUT); If you connect an LED and forget to set the pin to OUTPUT it will not work correctly. // variables to hold the times newSwitchState3 = digitalRead(pin_switch); When using interrupts on the Arduino; newSwitchState2 = digitalRead(pin_switch); // turn all LEDs off. // Because the value of state does not change while we are testing it we don't need to use else if, // Now using an array to store the LED pins, // Define the pins being used fro the LEDs. keyPressed = checkButtonSwitch(); { Let’s add more details to this analogy: the email you’re about to receive contains a special offer to get a discount on a given website – and this offer is available only for 2 minutes. }. If the code is unnecessarily complex you may be able to copy and paste it but you won’t understand it and so you won’t be able to adapt it to your own needs. if (newSwitchState != LEDstate) { newSwitchState1 = digitalRead(pin_switch); { The best way to print something from an interrupt, is simply to set a flag inside the interrupt, and poll this flag inside the main loop() program. oldSwitchState = newSwitchState1; We store the previous time, then get the current time. Serial.println(" "); The compiler does many things to optimize the code and the speed of the program. These then become local variables. This is an extremely common method for switch debouncing. } Here I cover some of the ways I do it using a single button switch. // variables to hold the new and old switch states To ensure the Arduino (actually the compiler) always uses the latest value we declare the variable as volatile. } After the triggered function is done, the main execution resumes. Polling. if ( flashingLEDisON == false) } { digitalWrite(pin_LED, HIGH); Serial.println(" "); Polling. pinMode(pin_led, LOW); // Pins Note that we are using the pin 3 for the button. boolean LEDstatus = LOW; Using interrupts can become complex and tricky quite quickly but if you have ever done any event driven programming the techniques are similar. In this case, you could have a variable named “shouldMoveMotor” that you set to “true” in the interrupt function. unsigned long timeNow = 0; { Here, the main advantage you get is that there is no more polling for the button in the loop() function. { { Just enough to get you started turning things on and off. We are using exactly the same circuit as above. newSwitchState3 = digitalRead(pin_switch); Example 05: Start and stop an action whit two different led and bottons. pinMode(pin_LED, OUTPUT); // put your main code here, to run repeatedly: I also added a variable to store the sequence length. // Turn on the next LED Release the switch and the LED goes out. } } Inside the loop() function the state of the switch pin is checked. // turn on or turn off the blinking LED Polling. int pin_LED = 10; } Nothing really new here. Upload the sketch and give it a go. Here we changed the way we are monitoring the push button. I'll be posting more about the construction of the DAC in another instructable, for now I've included the photo's above. Now, lets look at the code. Thanks to Manuato for point this. if (state==3) { digitalWrite(pin_LEDred, HIGH); } boolean key = false; boolean newSwitchState1 = digitalRead(pin_switch); delay(1); As previously stated, on Arduino Uno you can only use pin 2 and 3 for interrupts. I was searching a lot until i found your guide that explained everything!!!! // { } Closing the button switch will complete the circuit and the LED will come. int pin_switch = 2; Normally connecting an Arduino pin directly to 5V can be a bad idea but we can do it here because Arduino digital pins that are set for INPUT with pinMode have a very high impedance similar to having a 100 megohm resistor in front of the pin. Maybe using millis() or micros() can sometimes be useful, if you want to make a comparison of duration (for example to debounce a button). } However, usually you can’t use all available digital pins. // An example of using a button switch as a toggle switch to turn an LED on or off Temperature and Humidity Monitor, Seeed Studio: W600 Module, Wio Lite W600, and Wio Lite MG126. else keyPressed = checkButtonSwitch(); Example 02: Turning an LED on and off with debounce, Switching things: Polling examples (1 to 5a), What Arduino Kit Should I buy? newSwitchState1 = digitalRead(pin_switch); What I recommend you to do is to only change state variables inside interrupt functions. newSwitchState3 = digitalRead(pin_switch); With interrupts, you’re sure that you won’t miss the trigger.