Assignment 2: Button Input

Navigate to workshops/2025-10-17 directory and open Assignment 2 in the MicroPython Jupyter Notebook browser interface.

If prompted with selecting kernel, select Embedded Kernel, click on the ESP Control Panel and connect your device.

In this assignment, you will learn to read button inputs and generate interactive responses with LEDs.

Understanding Pull-up Resistors

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On the ESP32-C3-DevKit-RUST-2 board, pressing the boot button connects pin 9 to ground. When the button is not pressed, the pin is left floating, which leads to an undefined logic level. Pull-up resistors ensure that the pin maintains a defined logic high level when the button is released.

In summary:

• Button not pressed: GPIO reads HIGH (1) thanks to pull-up resistor.
• Button pressed: GPIO reads LOW (0) because the pin is connected to ground.

The ESP32-C3-DevKit-RUST-2 has internal pull-up resistors that can be enabled in software.

Task 1: Configure button

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In this task, you’ll initialize the onboard button so your program can read its state. The pin is configured as an input (machine.Pin.IN) with an internal pull-up resistor (machine.Pin.PULL_UP).

button = machine.Pin(9, machine.Pin.IN, machine.Pin.PULL_UP)

Task 2: Simple Button Press Detection

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Here you’ll write a function that waits until the button is pressed. The loop continuously checks the pin’s value — when it changes from HIGH to LOW, the program detects a press and prints a message.

def wait_for_button_press():
    """Wait until button is pressed"""
    while button.value() == 1:
        time.sleep(0.05)
    print("Button pressed!")

Now you’ll make the LED respond to button input. Each time the button is pressed, the LED toggles between ON and OFF. A small delay is added to handle “debouncing” — preventing multiple rapid triggers from one press.

Task 3: Toggle LED on Button Press

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led_state = False

while True:
    if button.value() == 0:  # Button pressed
        led_state = not led_state
        if led_state:
            set_color(255, 0, 0)
        else:
            clear_led()

        # Wait for button release (debounce)
        while button.value() == 0:
            time.sleep(0.05)
        time.sleep(0.1)  # Additional debounce delay

Task 4: Measure Press duration

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In this task, you’ll measure how long the button is held down. The program records the start time when pressed and calculates the total duration once released.

def measure_press_duration():
    """Measure how long the button is held down"""
    start = time.ticks_ms()
    while button.value() == 0:
        time.sleep(0.05)
    duration = time.ticks_diff(time.ticks_ms(), start) / 1000.0
    return duration

wait_for_button_press()
duration = measure_press_duration()
print(f"Button held for {duration:.2f} seconds")

Bonus Challenge

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Create a visual feedback based on duration.

Change LED color based on how long the button is pressed:

• Short press (< 1s): Blue
• Medium press (1-3s): Yellow
• Long press (> 3s): Red

Next step

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Next step: Assignment 3.