bouton-led.ino
A button wired to GND lights the LED while pressed. INPUT_PULLUP enables the internal resistor, and the 30 ms window filters the contact's mechanical bounce.
Hardware required
An Arduino Mega ADK Rev3 (ATmega2560 + MAX3421E USB host chip with a Type-A port; digital pin 7 is reserved for the MAX3421E reset). 1 push button.
Wiring
One button leg on pin 2, the other to GND; LED (with 330 Ω resistor) on pin 13 if external.
How it works
A reading counts only after 30 ms of stability; pressing pulls the pin to ground (LOW with pull-up) and lights the LED. Select « Arduino Mega ADK » in the IDE. For USB host/ADK work, install the USB Host Shield 2.0 library; do not use D7. The USB-A port powers the accessory at 5 V.
Going further
Turn it into a toggle by flipping a state on each edge, or wire a second button on pin 3.
bouton-led.ino
// Bouton sur la broche 2 (vers GND) + LED sur 13, anti-rebond logiciel.
const int BOUTON = 2;
const int LED = 13;
const unsigned long ANTI_REBOND = 30; // ms
bool dernier = HIGH, stable = HIGH;
unsigned long bord = 0;
void setup() {
pinMode(BOUTON, INPUT_PULLUP); // resistance interne : rien d'externe
pinMode(LED, OUTPUT);
Serial.begin(9600);
}
void loop() {
bool lu = digitalRead(BOUTON);
unsigned long t = millis();
if (lu != dernier) bord = t;
if (t - bord >= ANTI_REBOND && lu != stable) {
stable = lu;
digitalWrite(LED, stable == LOW ? HIGH : LOW);
Serial.println(stable == LOW ? F("Appui") : F("Lache"));
}
dernier = lu;
}