🛠 Transformer le Micro en clavier USB (HID) avec bouton de sécurité

Objectives

Leverage the Micro's specificity: the ATmega32U4 is itself the USB peripheral (no coprocessor). The board can therefore type on the keyboard via the Keyboard class, provided you keep a physical safety button to never hijack the host's keyboard.

Hardware

• 1 Arduino Micro + micro-USB cable
• 1 push button between pin 2 and GND
• A computer with a text editor open and focused

Complete code

// Micro clavier USB : tape un message quand le bouton (broche 2) est presse.
// Pattern officiel KeyboardMessage : la frappe ne part que sur appui deliberé.
#include <Keyboard.h>

const uint8_t BTN = 2;   // bouton vers GND, pull-up interne

void setup {
  pinMode(BTN, INPUT_PULLUP);
  Keyboard.begin;      // demarre l'interface HID clavier
}

void loop {
  if (digitalRead(BTN) == LOW) {   // actif-low
    delay(50);                     // anti-rebond
    if (digitalRead(BTN) == LOW) {
      Keyboard.print("Bonjour depuis mon Arduino Micro !");
      while (digitalRead(BTN) == LOW) {}  // un seul envoi par appui
    }
  }
}

Expected verification

Upon uploading, the Micro disappears and then reappears as a keyboard device. Pressing the button enters the message into the text editor that has focus. Unplugging the Micro immediately returns control to the real keyboard.

Common errors

• Sending keystrokes in setup without a safety button: the board hijacks the host's keyboard as soon as it starts; unplug it and reprogram.
• Forgetting that the HID keyboard is active from Keyboard.begin: the sketch must remain responsive to the button.
• Selecting the Leonardo board instead of Micro: uploading may work, but the pins (LED, RX_LED) differ.
• Expecting text in the Serial Monitor: here Serial is not used; the USB identity is keyboard (+ CDC depending on the core).