The first step with any new hardware is the 'hello world' of electronics - blinking an LED. This is very easy with CircuitPython and DragonBoard410c. 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
Some tactile buttons or switches:
Because the DragonBoard 410c uses 1.8V logic levels, you will need a logic level converter to interface with most peripherals.
We recommend using a breadboard and some male-male wires.
Wiring
- Connect the DragonBoard Ground pin to the blue ground rail on the breadboard
- Connect the DragonBoard +5V pin to the red 5V rail on the breadboard.
- Connect the DragonBoard +1.8V pin to the LV pin on the Logic Level Converter
- Connect the HV pin on the Logic Level Converter to the 5V rail
- Connect the Ground pin on the Logic Level Converter to the blue ground rail on the breadboard
- Connect one side of the tactile switch to the B1 pin on the Logic Level Converter
- Connect a ~10K pull up resistor from B1 to the 5V rail
- Connect the other side of the tactile switch to the ground rail
- Connect the longer/positive pin of the LED to the B2 pin on the Logic Level Converter
- 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
- Connect the DragonBoard GPIO_B pin (GPIO 12) to the A1 pin on the Logic Level Converter
- Connect the DragonBoard GPIO_A pin (GPIO 36) to the A2 pin on the Logic Level Converter
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.GPIO_A)
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 the correct Logic Level Converter channel, that the Logic Level channel is connected to GPIO_A or GPIO_36, the resistor is installed correctly, and you have a Ground wire to the DragonBoard. Also, be sure to check the Power and Ground wires to the Logic Level Converter.
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.GPIO_A)
led.direction = digitalio.Direction.OUTPUT
button = digitalio.DigitalInOut(board.GPIO_B)
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
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