🛠 Les 3 boutons A, B, C et le haut-parleur interne

Objectives

• Read the three programmable front-panel buttons: A = GPIO39, B = GPIO38, C = GPIO37.
• Use M5.update and the wasPressed / wasReleased methods from M5Unified.
• Make the 1 W speaker wired to the DAC output GPIO25 sound (tone, beep, mute).
• Display a press counter for each button on the screen.

Hardware

• 1 M5Stack Core (Basic or Gray).
• Nothing external: buttons and speaker are built-in.
• Note: GPIO39/38/37 are input-only pins (no internal pull-down) — perfect for buttons, unusable as outputs.

Complete code

#include <M5Unified.h>

uint32_t nbA = 0, nbB = 0, nbC = 0;

void setup {
  auto cfg = M5.config;
  M5.begin(cfg);
  M5.Speaker.setVolume(180);
  M5.Display.setTextSize(2);
  M5.Display.setTextColor(TFT_WHITE, TFT_BLACK);
  M5.Display.println("Boutons A / B / C");
}

void loop {
  M5.update;                       // indispensable avant wasPressed
  if (M5.BtnA.wasPressed) {
    nbA++;
    M5.Speaker.tone(2200, 100);      // 2,2 kHz pendant 100 ms
  }
  if (M5.BtnB.wasPressed) {
    nbB++;
    M5.Speaker.beep;
  }
  if (M5.BtnC.wasPressed) {
    nbC++;
    M5.Speaker.mute;
  }
  M5.Display.fillRect(0, 50, 320, 90, TFT_BLACK);
  M5.Display.setCursor(10, 55);
  M5.Display.printf("A : %lu\n", nbA);
  M5.Display.printf("B : %lu\n", nbB);
  M5.Display.printf("C : %lu\n", nbC);
  vTaskDelay(5 / portTICK_PERIOD_MS);
}

Expected verification

• Each press of A increments the A counter and emits a high-pitched beep; B emits a standard beep; C mutes the sound.
• The counters remain consistent (one press = +1, no visible bouncing thanks to M5Unified).
• The serial monitor is not necessary: all feedback is on the screen.

Common errors

• Forgetting M5.update in loop: wasPressed never returns true.
• Expecting buttons to work with pinMode(INPUT_PULLDOWN): GPIO37-39 pins have no internal pull-down; let M5Unified handle it.
• Using GPIO39/38/37 to control a component: these are input-only pins.
• Confusing the front-panel buttons with the red side button: the latter controls power via the IP5306 (double-click = shutdown), it is not readable by the program.
• Volume too low: call M5.Speaker.setVolume before any tone/beep.