🛠 Les 4 boutons du pavé comme sélecteurs de couleur

Objectives

Learn how to read digital inputs from the Esplora: the four push buttons arranged in a diamond (SWITCH_UP, SWITCH_DOWN, SWITCH_LEFT, SWITCH_RIGHT) plus the central joystick button. Each button will light up a different color on the RGB LED. You will also discover a specific pitfall of this board: these buttons are read via an analog multiplexer, not directly on GPIO pins.

Hardware

• An Arduino Esplora and its micro-USB cable.
• Arduino IDE 2.x with the arduino:avr core and the Esplora library.
• No external components: everything is on-board.

Complete Code

/* Chaque bouton du losange allume une couleur de la LED RVB.
   Les boutons ne sont pas sur des broches dédiées : la bibliothèque
   les lit sur un multiplexeur analogique (A0-A3 en adresse, A4 en ADC). */
#include <Esplora.h>

void setup {
  Serial.begin(9600);          // pour observer l'état des boutons
}

void loop {
  if (Esplora.readButton(SWITCH_UP) == PRESSED) {
    Esplora.writeRGB(255, 0, 0);        // haut = rouge
    Serial.println("UP");
  } else if (Esplora.readButton(SWITCH_DOWN) == PRESSED) {
    Esplora.writeRGB(0, 255, 0);        // bas = vert
    Serial.println("DOWN");
  } else if (Esplora.readButton(SWITCH_LEFT) == PRESSED) {
    Esplora.writeRGB(0, 0, 255);        // gauche = bleu
    Serial.println("LEFT");
  } else if (Esplora.readButton(SWITCH_RIGHT) == PRESSED) {
    Esplora.writeRGB(255, 255, 0);      // droite = jaune
    Serial.println("RIGHT");
  } else {
    Esplora.writeRGB(0, 0, 0);          // aucun bouton = éteinte
  }
  delay(50);
}

Expected Verification

Press each button: the LED takes on the corresponding color and the serial monitor (9600 baud) displays the button name. Release it: the LED turns off. Also test the central joystick button with Esplora.readButton(SWITCH_JOYSTICK) — note that, unlike the four diamond buttons, it does not have a hardware pull-up resistor; the library compensates by enabling a software pull-up when reading this channel.

Common Errors

1. Confusing PRESSED and HIGH: readButton returns PRESSED (internal logic circuit + multiplexing), never a simple HIGH from digitalRead.
2. Trying to read two buttons "at the same time": multiplexed channels share a single analog-to-digital converter; reading is sequential with settling time. Chaining readButton calls in the loop is designed for this, but do not hack interrupts on top of it.
3. Flaky joystick button: without the library's fix (software pull-up), it floats and triggers on its own — never use digitalRead on the common pin A4 for this button.
4. Forgetting the delay(50): without a small delay, you will flood the serial monitor with lines; multiplexing also needs this time between two channel changes.