digitalio module has many applications. The basic Blink program sets up the LED as a digital output. You can just as easily set up a digital input such as a button to control the LED. This example builds on the basic Blink example, but now includes setup for a button switch. Instead of using the
time module to blink the LED, it uses the status of the button switch to control whether the LED is turned on or off.
The red LED (highlighted above in red) is located above the USB jack on the left side of the board.
The Boot button (highlighted above in blue) is located next to the bottom left corner of the display, above the GND pin.
In the example below, click the Download Project Bundle button below to download the necessary libraries and the code.py file in a zip file. Extract the contents of the zip file, open the directory CircuitPython_Templates/digital_input_built_in_button_led/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.
Your CIRCUITPY drive should now look similar to the following image:
# SPDX-FileCopyrightText: 2022 Kattni Rembor for Adafruit Industries # SPDX-License-Identifier: MIT """ CircuitPython Digital Input Example - Blinking an LED using the built-in button. """ import board import digitalio led = digitalio.DigitalInOut(board.LED) led.direction = digitalio.Direction.OUTPUT button = digitalio.DigitalInOut(board.BUTTON) button.switch_to_input(pull=digitalio.Pull.UP) while True: if not button.value: led.value = True else: led.value = False
Now, press the button. The LED lights up! Let go of the button and the LED turns off.
Note that the code is a little less "Pythonic" than it could be. It could also be written as
led.value = not button.value. That way is more difficult to understand if you're new to programming, so the example is a bit longer than it needed to be to make it easier to read.
import two modules:
digitalio. This makes these modules available for use in your code. Both are built-in to CircuitPython, so you don't need to download anything to get started.
Next, you set up the LED. To interact with hardware in CircuitPython, your code must let the board know where to look for the hardware and what to do with it. So, you create a
digitalio.DigitalInOut() object, provide it the LED pin using the
board module, and save it to the variable
led. Then, you tell the pin to act as an
You include setup for the button as well. It is similar to the LED setup, except the button is an
INPUT, and requires a pull up.
Inside the loop, you check to see if the button is pressed, and if so, turn on the LED. Otherwise the LED is off.
That's all there is to controlling an LED with a button switch!