Class Overview

• intro to microcontrollers
• talking to your board
• inputs and outputs

So what's on your board?

• 10 x mini NeoPixels, each one can display any color
• 1 x Motion sensor (LIS3DH triple-axis accelerometer with tap detection, free-fall detection)
• 1 x Temperature sensor (thermistor)
• 1 x Light sensor (phototransistor). Can also act as a color sensor and pulse sensor.
• 1 x Sound sensor (MEMS microphone)
• 1 x Mini speaker with class D amplifier (7.5mm magnetic speaker/buzzer)
• 2 x Push buttons, labeled A and B
• 1 x Slide switch
• Infrared receiver and transmitter - can receive and transmit any remote control codes, as well as send messages between Circuit Playground Expresses. Can also act as a proximity sensor.
• 8 x alligator-clip friendly input/output pins
• Includes I2C, UART, 8 pins that can do analog inputs, multiple PWM output
• 7 pads can act as capacitive touch inputs and the 1 remaining is a true analog output
• Green "ON" LED so you know its powered
• Red "#13" LED for basic blinking
• Reset button
• ATSAMD21 ARM Cortex M0 Processor, running at 3.3V and 48MHz
• 2 MB of SPI Flash storage, used primarily with CircuitPython to store code and libraries.
• MicroUSB port for programming and debugging
• USB port can act like serial port, keyboard, mouse, joystick or MIDI!

Ground Rules:

• your code lives on your microcontroller
• code lives in code.py
• runs when you save
• formatting matters

print('Hello, World')

Find a partner, and get your board to say hello to them.

print('Hello, World')

Now let's add some structure to it.

import time 

while True: 
    print("hello")
    time.sleep(1)

print("I never print")

Okay, let's control some hardware.

import board
import digitalio
import time

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

while True:
    led.value = True
    time.sleep(0.1)
    led.value = False
    time.sleep(0.5)

That was output. Let's do some input.

import time
import board
import digitalio

led = digitalio.DigitalInOut(board.D13)
led.switch_to_output()

button = digitalio.DigitalInOut(board.BUTTON_A)
button.switch_to_input(pull=digitalio.Pull.DOWN)

while True:
    if button.value:  # button is pushed
        led.value = True
    else:
        led.value = False

    time.sleep(0.01)

Example Code

Some exercises to try ...

• Try using the second button. Can you make the LED only light up when both buttons are pressed?
• Can you make a light that turns on if one button is pressed, and turns off if the other one is?
• Can you make the board say "hello" when a button is pressed?

Did you make the board say hello? What happened?

import time
import board
import digitalio

button = digitalio.DigitalInOut(board.BUTTON_A)
button.switch_to_input(pull=digitalio.Pull.DOWN)

while True:
    print(button.value)
    time.sleep(0.1)

Pair up with someone and see if you can solve that issue.

(5 mins)

We have to do something only when the button value changes.

button = digitalio.DigitalInOut(board.BUTTON_A)
button.switch_to_input(pull=digitalio.Pull.DOWN)

lastValue = button.value

while True:
    if (button.value == True) and (lastValue == False):
        print("Only prints once per button press")
    lastValue = button.value
    
    time.sleep(0.1)

This is called edge detection. Example code

import time
import board
import neopixel

pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=0.1, auto_write=False)
RED = (255, 0, 0)
OFF = (0, 0, 0)

while True:
    pixels.fill(RED)
    pixels.show()
    time.sleep(1)

Neopixel Challenges:

• Turn the whole board your favorite color
• Make every other pixel a different color
• Make the whole board flash 2 different colors

Challenges Pt 2

• Animate a pixel in a circle around the board
• Use a button press and your neopixels together
• Use your neopixels to count the number of button presses

Addressing multiple pixels at a time:

    indices = [0, 2, 4]
    for i in indices:
        pixels[i] = CYAN

What we learned:

• What's a microcontroller
• Intro to Mu
• Intro to CircuitPython
• Buttons, I/O, Serial Monitor
• Edge Detection
• Libraries
• Intro to Neopixel

Resources:

• Check out the Adafruit CircuitPython Examples, specifically the Light Sensor, Sound Meter, and Temperature Sensors.