Teensyduino-1Button-Keyboard.ino

#include <Bounce.h>

Bounce button = Bounce(1, 10);

void setup() {
  pinMode(1, INPUT_PULLUP);
}

void loop() {
  button.update();
  
  if (button.fallingEdge()) {
    Keyboard.set_modifier(MODIFIERKEY_GUI);
    Keyboard.set_key1(KEY_D);
    Keyboard.send_now();
  }

  if (button.risingEdge()) {
    Keyboard.set_modifier(0);
    Keyboard.set_key1(0);
    Keyboard.send_now();
  }
}