🛠 Bouton poussoir et console série sur le GIGA R1

Objectives

Learn how to read a digital input using an internal pull-up resistor and communicate with the PC via the GIGA R1's USB-C serial port. You will also discover a documented pitfall of the Mbed core: native printf does not output to the USB serial port (issue #958); you must use Arduino's Serial object.

Hardware

• 1 Arduino GIGA R1 WiFi board
• 1 push button
• 1 USB-C data cable
• No resistor required: we enable the internal pull-up

Complete code

// GIGA R1 WiFi — bouton poussoir + console série
#include <Arduino.h>

const int BOUTON = D2;      // bouton entre D2 et GND (pull-up interne activé)

void setup {
  Serial.begin(115200);     // console série sur USB-C
  pinMode(BOUTON, INPUT_PULLUP);
  Serial.println("Appuyez sur le bouton !");
}

void loop {
  if (digitalRead(BOUTON) == LOW) {   // contact fermé -> LOW (pull-up)
    Serial.println("Bouton appuyé !");
    delay(200);                       // anti-rebond logiciel simple
  }
}

Connect one leg of the button to pin D2 and the other leg to GND. The potential is held high by the internal pull-up as long as the button is open.

Expected verification

At startup, the Serial Monitor (115200 baud) displays "Press the button!". Each press displays "Button pressed!" with a rate limited by the 200 ms debounce. Releasing the button produces no line.

Common errors

• Logic confusion: with INPUT_PULLUP, the signal is LOW when pressed, not HIGH.
• Button connected between the pin and 3.3 V without a resistor: short circuit or inverted reading.
• Expecting output from a C printf("...") in the Serial Monitor: on the GIGA's Mbed core, printf does not reach the USB serial port (bug #958, fixed since); always use Serial.print.
• Serial Monitor closed or wrong baud rate: no visible output.
• Forgetting the delay(200) debounce: bursts of phantom presses.