Wiring the Buttons

Six momentary tactile push buttons let you interact with the clock — setting alarms, snoozing, dismissing, and navigating menus.

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How Buttons Work

Each button connects one GPIO pin to GND through a simple switch:

3.3 V ── [internal 45kΩ pull-up] ── GPIO pin ──┬── GND (via button, when pressed)
                                                 │
                                                 └── (open, when not pressed)

• Not pressed: GPIO reads HIGH (3.3 V, pulled up)
• Pressed: GPIO reads LOW (connected to GND)

The ESP32-S3 has built-in ~45 kΩ pull-up resistors that can be enabled in firmware, so no external resistors are needed.

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Pin Table

Button	Function	Wire colour	ESP32-S3 pin label	GPIO #
BTN_UP	Increment value / scroll up	Green	GPIO6	6
BTN_DOWN	Decrement value / scroll down	Green	GPIO7	7
BTN_SELECT	Confirm / enter submenu	Green	GPIO8	8
BTN_BACK	Cancel / go back	Green	GPIO9	9
BTN_SNOOZE	Snooze active alarm	Green	GPIO38	38
BTN_DISMISS	Dismiss active alarm	Green	GPIO39	39

Each button has two terminals. Connect one terminal to the GPIO pin and the other to GND. The two terminals are interchangeable — polarity does not matter for a simple switch.

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Circuit Diagram

The schematic shows all six buttons. Each button connects a GPIO pin to GND. The dashed resistors represent the ESP32's internal pull-ups (~45 kΩ) — no external resistors are needed for this project.

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Wiring Diagram

All buttons share the GND rail — run one wire from the ESP32's GND pin to the breadboard GND rail, then connect all button GND terminals to that rail.

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Verification

Flash a minimal button test that prints the button name on press:

// Configure GPIO6 as input with pull-up
gpio_config_t cfg = {
    .pin_bit_mask = (1ULL << GPIO_NUM_6),
    .mode         = GPIO_MODE_INPUT,
    .pull_up_en   = GPIO_PULLUP_ENABLE,
    .intr_type    = GPIO_INTR_DISABLE,
};
gpio_config(&cfg);

// Poll in a loop
while (1) {
    if (gpio_get_level(GPIO_NUM_6) == 0) {
        printf("BTN_UP pressed\n");
        vTaskDelay(pdMS_TO_TICKS(200));  // simple debounce
    }
    vTaskDelay(pdMS_TO_TICKS(10));
}

Press each button and confirm the correct message appears. The button driver doc replaces this polling loop with interrupt-driven debounce.

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Gotchas

Do not use GPIO0 — it is a strapping pin. Holding it LOW when the ESP32 powers on enters bootloader mode instead of running firmware. If you accidentally use GPIO0 for BTN_UP and press it during power-on, the ESP32 will not start.

No pull-ups on ESP32-classic GPIO 34–39 — if you are using a classic ESP32 (not S3) and choose GPIO 34–39 for BTN_SNOOZE and BTN_DISMISS, you must add external 10 kΩ pull-up resistors to 3.3 V. The ESP32-S3 does not have this limitation for these pins.

Debouncing is required in firmware — a mechanical button contact bounces (rapidly opens and closes) for 5–50 ms when pressed. Without debouncing, one physical press generates dozens of events. The button driver doc handles this with a FreeRTOS timer.