The first step with any new hardware is the 'hello world' of electronics - blinking an LED. This is very easy with CircuitPython and Jetson Nano. 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 220 to 2.2K resistor
Some tactile buttons or switches along with some pull-up resistors:
We recommend using a breadboard and some male-male wires.
Wiring
- Connect the Jetson Nano Ground pin to the blue ground rail on the breadboard.
- Connect one side of the tactile switch to Jetson Nano D4 (#7)
- Connect a ~1K-10K pull up resistor from D4 to 3.3V
- Connect the other side of the tactile switch to the ground rail
- Connect the longer/positive pin of the LED to Jetson Nano D18 (#12)
- Connect the shorter/negative pin of the LED to a 220 ohm-2.2K resistor, the other side of the resistor goes to ground rail
There's no Jetson Nano Fritzing object, so we sub'd a Raspberry Pi in
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, let's 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.D18)
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 the resistor is installed correctly, and you have Ground and +3.3v wires to the Jetson Nano. Also, check that the wires are going to the correct GPIO pins. If you are powering the board with an AC adapter, try powering it through the USB port.
Type Control-C to quit
Button It Up
Now that you have the LED working, let's 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.D18)
led.direction = digitalio.Direction.OUTPUT
button = digitalio.DigitalInOut(board.D4)
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
