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Micropython Basics: Digital Inputs

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Now that you can save and manage your scripts, it’s time to interact with the real world using digital inputs. One of the simplest and most common examples is reading the state of a push button to control an LED.

In MicroPython, digital inputs and outputs are handled through the machine module, which provides access to the hardware pins of your microcontroller.

What Are Digital Inputs?

A digital input reads either a HIGH or LOW signal (1 or 0). These two states correspond to:

  • HIGH (1): Voltage is present on the pin (usually 3.3V or 5V).
  • LOW (0): Voltage is absent or connected to ground (0V).

Buttons, switches, and sensors (like infrared detectors) often output these digital signals. When pressed or triggered, they change the signal level, which MicroPython can read and respond to.

✅ Example Use Cases: Reading a button press, motion detection, or limit switches in robotics — all rely on digital input detection.

Hardware Setup: Button and LED

You’ll need the following components for this example:

  • 1 × MicroPython-compatible board (ESP32, ESP8266, or Raspberry Pi Pico)
  • 1 × Push button
  • 1 × LED
  • 1 × 330 Ω resistor (for the LED)
  • 1 × 10 kΩ pull-down resistor (optional if not using internal pull-up)
  • Breadboard and jumper wires

Wiring Guide

Connect the components as follows:

  • LED anode (long leg) → GPIO pin (e.g., GP15)
  • LED cathode (short leg) → resistor → GND
  • Button one leg → GPIO pin (e.g., GP14)
  • Button other leg → 3.3V (or use a pull-down resistor to GND)

When the button is pressed, the pin connected to it reads HIGH. When released, it reads LOW.

💡 Tip: Most MicroPython boards (like ESP32 and Pico) support internal pull-up or pull-down resistors. You can enable these in code without needing external resistors, which simplifies wiring.

How MicroPython Reads Digital Inputs

MicroPython uses the Pin class from the machine module to configure a GPIO pin as either an input or output.

For digital inputs, you can specify whether the pin should use an internal pull-up or pull-down resistor: 


from machine import Pin

# Configure a pin as an input with internal pull-down resistor
button = Pin(14, Pin.IN, Pin.PULL_DOWN)

# Read the state of the pin
state = button.value()
print(state)

The .value() method returns 1 when the button is pressed (HIGH) and 0 when released (LOW).

Combining Input and Output

You can combine a button input and an LED output to make a simple interactive project. For example, when the button is pressed, the LED turns on; when released, it turns off. 


from machine import Pin
import time

led = Pin(15, Pin.OUT)
button = Pin(14, Pin.IN, Pin.PULL_DOWN)

while True:
    if button.value() == 1:
        led.on()
    else:
        led.off()
    time.sleep(0.05)

This loop constantly checks the button state and controls the LED accordingly. The short delay (0.05s) helps reduce flickering.

⚙️ Note: Some buttons may cause “bouncing” — rapid ON/OFF signals when pressed or released. This is normal for mechanical switches and can be fixed by adding a short delay or software debounce.

Debouncing Buttons

Debouncing ensures that only one input is registered per button press. You can implement it by adding a small delay after a button is detected, or by checking if the state remains stable over time.

For example, you might read the button state twice with a short delay in between, and only accept the press if both readings are identical.

✅ Pro Tip: For more advanced debounce handling, you can use the machine.Timer class or event-based callbacks with interrupts (Pin.IRQ_FALLING and Pin.IRQ_RISING).

Testing and Troubleshooting

  • Make sure your button wiring matches the pin configuration (pull-up or pull-down).
  • If the LED doesn’t respond, double-check your GPIO pin numbers.
  • Use the REPL to print out button.value() to confirm input readings.
⚠️ Warning: Always check your board’s voltage tolerance before connecting components. Some pins (especially on ESP8266) do not support 5V inputs.

Summary

In this section, you learned how MicroPython handles digital inputs using the machine.Pin class. You built a simple button-controlled LED circuit and understood how HIGH/LOW logic works on GPIO pins.

This foundation is essential for building interactive projects — next, we’ll explore how to work with analog inputs to read variable signals such as those from potentiometers or sensors.

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