71 lines
2.3 KiB
C++
71 lines
2.3 KiB
C++
/*
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State change detection (edge detection)
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Often, you don't need to know the state of a digital input all the
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time, but you just need to know when the input changes from one state
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to another. For example, you want to know when a button goes from
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OFF to ON. This is called state change detection, or edge detection.
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This example shows how to detect when the built-in button changes
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from off to on and on to off.
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To use this example, connect to the Maple using the USB serial port.
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Then push the button a few times and see what happens.
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created 27 Sep 2005
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modified 30 Dec 2009
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by Tom Igoe
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Ported to the Maple 27 May 2010
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by Bryan Newbold
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*/
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// Variables will change:
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int buttonPushCounter = 0; // counter for the number of button presses
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int buttonState = 0; // current state of the button
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int lastButtonState = 0; // previous state of the button
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void setup() {
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Serial.begin(115200); // Ignored by Maple. But needed by boards using hardware serial via a USB to Serial adaptor
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// initialize the button pin as a input:
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pinMode(BOARD_BUTTON_PIN, INPUT);
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// initialize the LED as an output:
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pinMode(33, OUTPUT);
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}
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void loop() {
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// read the pushbutton input pin:
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buttonState = digitalRead(BOARD_BUTTON_PIN);
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// compare the buttonState to its previous state
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if (buttonState != lastButtonState) {
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// if the state has changed, increment the counter
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if (buttonState == HIGH) {
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// if the current state is HIGH, then the button went from
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// off to on:
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buttonPushCounter++;
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Serial.println("on");
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Serial.print("number of button pushes: ");
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Serial.println(buttonPushCounter, DEC);
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}
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else {
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// if the current state is LOW, then the button went from
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// on to off:
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Serial.println("off");
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}
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// save the current state as the last state, for next time
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// through the loop
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lastButtonState = buttonState;
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}
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// turns on the LED every four button pushes by checking the
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// modulo of the button push counter. Modulo (percent sign, %)
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// gives you the remainder of the division of two numbers:
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if (buttonPushCounter % 4 == 0) {
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digitalWrite(33, HIGH);
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} else {
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digitalWrite(33, LOW);
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}
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}
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