The first step with any new hardware is the 'hello world' of electronics - blinking an LED. This is very easy with CircuitPython and Odroid. We'll extend the example to also show how to wire up a button/switch.

Parts Used

Any old LED will work just fine as long as it's not an IR LED (you can't see those) and a 470 to 2.2K resistor

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Some tactile buttons or switches:

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We recommend using a breadboard and some female-male wires.

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You can use a Cobbler to make this a little easier, the pins will be labeled according to Raspberry Pi names so just check the Odroid name!

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Wiring

Connect the Odroid Ground pin to the blue ground rail on the breadboard.

  • Connect one side of the tactile switch to Odroid GPIO 249 which is also called D7
  • Connect a ~10K pull up resistor from D7 to 3.3V
  • Connect the other side of the tactile switch to the ground rail
  • Connect the longer/positive pin of the LED to Odroid GPIO 238 which is also called D1
  • Connect the shorter/negative pin of the LED to a 470ohm to 2.2K resistor, the other side of the resistor goes to ground rail

Double-check you have the right wires connected to the right location, it can be tough to keep track of GPIO pins as there are forty of them!

No additional libraries are needed so we can go straight on to the example code

However, we recommend running a pip3 update!

sudo pip3 install --upgrade adafruit_blinka

Blinky Time!

The finish line is right up ahead, lets start with an example that blinks the LED on and off once a second (half a second on, half a second off):

import time
import board
import digitalio

print("hello blinky!")

led = digitalio.DigitalInOut(board.D1)
led.direction = digitalio.Direction.OUTPUT

while True:
    led.value = True
    time.sleep(0.5)
    led.value = False
    time.sleep(0.5)

Verify the LED is blinking. If not, check that it's wired to GPIO 238 or D1, the resistor is installed correctly, and you have a Ground wire to the Odroid.

Type Control-C to quit

Button It Up

Now that you have the LED working, lets add code so the LED turns on whenever the button is pressed

import time
import board
import digitalio

print("press the button!")

led = digitalio.DigitalInOut(board.D1)
led.direction = digitalio.Direction.OUTPUT

button = digitalio.DigitalInOut(board.D7)
button.direction = digitalio.Direction.INPUT
# use an external pullup since we don't have internal PU's
#button.pull = digitalio.Pull.UP

while True:
    led.value = not button.value # light when button is pressed!

Press the button - see that the LED lights up!

Type Control-C to quit

This guide was first published on Jun 16, 2019. It was last updated on Jun 16, 2019.

This page (Digital I/O) was last updated on Apr 12, 2021.

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