Only print when the button is pressed and not being pressed anymore

Question

I have an Arduino and a microswitch that I want to use to know when the switch is initially being pressed (get "OnsetTime" on Serial) and when the switch is not being pressed anymore (get "OffsetTime" on Serial).

Imagine a bird sitting on the switch. I want to get an output "OnsetTime" when the bird first sits on the switch and an output "OffsetTime" when the bird flies away from the switch.

Right now, I have an output that constantly prints out "OnsetTime" when the switch is pressed. I would appreciate it if anybody can help me figure out how can I implement the below code to get the outputs only when the switch is initially pressed and not being pressed anymore.

void setup() {
  pinMode(7, INPUT);
  Serial.begin(9600);
}

void loop() {  
  if (digitalRead(7) == HIGH) {
    Serial.println("OnsetTime");
    }
}
    //Serial.println("GetOffsetTime");

Answer 1

You can save the value of the switch read to compare it on the next loop. This way you're able to detect changes.

int lastValue;

void setup() {
  pinMode(7, INPUT);
  lastValue= digitalRead(7);

  Serial.begin(9600);
}

void loop() {
  int currentValue = digitalRead(7);
  if (lastValue != currentValue) {
    lastValue = currentValue;

    if (currentValue == HIGH) {
      Serial.println("OnsetTime");
    } else {
      Serial.println("OffsetTime");
    }
  }
}

Please be aware that switches bounce. If you see multiple messages at each mechanical change, insert a delay(...).

Answer 2

If you want to be simple, you can use this library. The code will be

#include <ezButton.h>

ezButton button(7);  // create Button object that attach to pin 7;

void setup() {
  Serial.begin(9600);
  button.setDebounceTime(100); // set debounce time to 100 milliseconds
}

void loop() {
  button.loop(); // MUST call the loop() function first

  if(button.isPressed())
    Serial.println("OnsetTime");

  if(button.isReleased())
    Serial.println("GetOffsetTime");
}

If you want to understand in depth, You can see the code and instruction in this tutorial