Published November 8, 2018

Circuit Playground Express

This is an overview of how to use and code the sensors on the Circuit Playground Express. I am using MakeCode.

BeginnerProtip1 hour3,685

Things used in this project

Hardware components

Adafruit Circuit Playground Express Advanced Pack

This is the one I have but there are other versions. I've also adde the basic version below.

Adafruit Circuit Playground Express

Software apps and online services

Microsoft MakeCode

Story

Circuit Playground Express (CPE) and MakeCode

When I get really excited to do a project or I am teaching people how to start out with electronics, I just want to dive right in. With learners, I want them to have a quick win and experience the joy of making. CPE lets them light up neopixels or read data from onboard sensors using drag and drop code. I don't have to teach them the directionality of a diode, the debounce of a button, or the difference between data types. Those are all important and valuable skills, but this system will allow them to focus on the big picture before getting caught in the weeds.

The board's capabilities can expand along with the users as they learn. The CPE has 6 built-in sensors. Users can add more sensors and actuators using the 7 analog/GPIO pins. The board can be programmed with MakeCode (JavaScript), Circuit Python, or Arduino IDE (C).

MakeCode is a drag and drop graphical way to create code. It allows you to play with the logical flow of a code without needing to know all the syntax. The blocks are puzzle pieces which provide the structure of the code.

In this tutorial, I will focus on using sensors and MakeCode. There are three actions that you can accomplish with sensors. You can trigger events, set thresholds, and read inputs.

Events

Events are triggered by certain values read from a sensor. When an event is triggered, it interrupts the normal flow of the program. If the code is performing steps inside the forever block, it will stop what it is doing switch to the event block. Events have the same shape as the start and forever blocks (they are all functions). Events contain a list of steps to be performed once the event is initiated.

Thresholds

Thresholds can set a value that would trigger an event. For example, you can set a threshold for the light sensor. The light sensor reads values from 0 to 255. You can set a threshold that says anything below 160 is considered dark. Any time the light sensor reading crosses the threshold from light to dark, the event for darkness is triggered. If the sensor is continuously reading below 160, the event only occurs once.

Threshold blocks go inside of the start or forever blocks. I typically put them inside the start block since I only set them once. If you are using a variable to set your threshold, then it would make sense to go in the forever block.

ReadInputs

Analog sensors have an analog read block. These blocks are round in shape. The sensors have different ranges of values they return. The light, microphone, and capacitive touch buttons return values from 0 to 255 (8 bit ADC converter). The accelerometer goes from 0 to 1023 (10 bit converter). The temperature sensor displays the temperature in degrees and not the raw voltage values like the other sensors. The IR sensor reads numbers from the transmitter.

The A and B button and the slider are digital inputs. They read a true or a false. The capacitive touch sensors can be digital or analog. The digital read is a comparator that is a diamond-like shape.

Accelerometer

The threshold of the accelerometer can be set to 1g, 2g, 4g, or 8g. The analog input can read the value for the x, y, or z axis. There is also an option to read the strength of the accelerometer. This is the vector value of the x, y, and z directions.

There are several events that can be triggered. I love that you don't have to code what the accelerometer would read when tilted, flipped, shook, or dropped. There are 11 types of events that the accelerometer can trigger.

Below is a video explaining and demonstrating the events that can be triggered by the accelerometer.

Code Example and Demonstration

This is a link to the published code - https://makecode.com/_bDkP0p8ffAJj

1 / 4 • MakeCode for the accelerometer example.

Buttons

There are two physical buttons, a physical switch, and seven capacitive touch pins. The physical buttons and switch are digital sensors. They are read as either on or off. The capacitive touch pins can be read as a digital or analog input. Since the captive touch pin can be analog, a threshold can be set for them. There are four ways to trigger a button on up, down, click, and long click.

MakeCode Example for buttons.

This is the link to the published example of the button MakeCode -- https://makecode.com/_XEL81YE18Epj

1 / 3 • MakeCode for the button example.

Infrared Sensor (IR)

The CPE boards have an IR transmitter and receiver. They can send information to each other via the IR sensor. The transmitter can send a number. When a number is sent, the IR reciever triggers an event. This number is then a variable you can use in your code.

MakeCode example for the IR sensor.

This is the link to the published example of the button MakeCode -- https://makecode.com/_ce5V9VExj7s6

1 / 3 • MakeCode example for IR sensor.

Light

The light sensor can read the levels of ambient or brightness. Light level is an analog input from 0 to 255 that purely read the brightness. A threshold can be set for light or darkness. An event can then be triggered if this threshold is crossed. You can have a separate event and threshold for both bright and dark.

The ambient reading reads RGB vales. Each of the three have 256 options. This means the ambient light is represented by 16, 777, 216 options (0-16, 777, 215).

MakeCode example for light sensor.

This is the link to the published example of the light MakeCode --https://makecode.com/_a9m43phqRcCW

1 / 5 • MakeCode for light sensor example.

Microphone

There is a microphone sensor. The threshold can be set, an event can be triggered when a loud noise is registered, and the analog value can be read. The threshold can be set from 0 to 100. However, the sensor ranges from 0 to 255. I was unable to trigger an event except for the initial moment of powering the board.

MakeCode example for microphone sensor.

This is the link to the published example of the microphone MakeCode -- https://makecode.com/_X1t9Fc7s21zk

1 / 3 • MakeCode for the microphone example.

Temperature

The temperature sensor reads degrees in Fahrenheit and Celsius. Events can be triggered when the sensor value crosses either a cold or hot threshold.

MakeCode example for the temperature sensor.

This is the link to the published example of the temperature MakeCode -- https://makecode.com/_iiVRR5M08KWq

1 / 3 • MakeCode for the temperature sensor.

Code

MakeCode Example

// This event is triggered when the accelerometer
// detects a shaking motion.
input.onGesture(Gesture.Shake, function () {
    // A sound is played when the board detects that it is
    // shook.
    music.playSoundUntilDone(music.sounds(Sounds.PowerUp))
})
// This event is triggered when the accelerometer
// detects that the board is tilted down.
input.onGesture(Gesture.TiltDown, function () {
    // A sound is played when the board is tilted down.
    music.playSoundUntilDone(music.sounds(Sounds.JumpDown))
})
// This event is triggered when the accelerometer
// detects that the board is tilted upwards.
input.onGesture(Gesture.TiltUp, function () {
    // A sound is played when the board is tilted upwards.
    music.playSoundUntilDone(music.sounds(Sounds.JumpUp))
})
// This event is triggered when the accelerometer
// detects that the board is tilted to the left.
input.onGesture(Gesture.TiltLeft, function () {
    // A sound is played when the board is tilted to the
    // left.
    music.playTone(349, music.beat(BeatFraction.Half))
})
// This event is triggered when the accelerometer
// detects when the board is flipped face up.
input.onGesture(Gesture.FaceUp, function () {
    // A sound is played when the board overtime the board
    // is flipped face up.
    music.playTone(131, music.beat(BeatFraction.Half))
})
// This event is triggered when the accelerometer
// detects that the board is tilted to the right.
input.onGesture(Gesture.TiltRight, function () {
    // A sound is played when the board is tilted to the
    // right.
    music.playTone(988, music.beat(BeatFraction.Half))
})
// This event is triggered when the accelerometer
// detects when the board is flipped face down.
input.onGesture(Gesture.FaceDown, function () {
    // A sound is played when the board is flipped faced
    // down.
    music.playSoundUntilDone(music.sounds(Sounds.BaDing))
})
// This event is triggered when the accelerometer
// detects that the board is in free fall.
input.onGesture(Gesture.FreeFall, function () {
    // A sound is played when the board is in free fall.
    music.playSoundUntilDone(music.sounds(Sounds.Wawawawaa))
})
// This event is triggered when the accelerometer hits
// 8g.
input.onGesture(Gesture.EightG, function () {
    // A sound is played when the board reaches 8g.
    music.playSoundUntilDone(music.sounds(Sounds.MagicWand))
})
// This event is triggered when the accelerometer hits
// 3g.
input.onGesture(Gesture.ThreeG, function () {
    // A sound is played when the board reaches 3g.
    music.playSoundUntilDone(music.sounds(Sounds.Siren))
})
// This set the threshold for the accelerometer.
input.setAccelerometerRange(AcceleratorRange.OneG)
// Forever loops the step inside this block, well,
// forever. Events interrupts the steps in this block.
// In this example, the rotation of the board is
// graphed in neopixels. The lower the degrees, the
// fewer pixels are lit. It also logs the x value of
// acceleration.
forever(function () {
    // This graphs the rotation of the board. The higher
    // the angle, the more neopixels are lit.
    light.graph(input.rotation(Rotation.Pitch))
    // This logs the value of acceleration in the x
    // direction.
    console.logValue("x", input.acceleration(Dimension.X))
})

Credits

SciJoy

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Circuit Playground Express

Things used in this project

Hardware components

Software apps and online services

Story

Circuit Playground Express (CPE) and MakeCode

Accelerometer

Buttons

Infrared Sensor (IR)

Light

Microphone

Temperature

Schematics

Pinouts of Circuit Playground Express

Code

MakeCode Example

Credits

SciJoy

Comments

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Circuit Playground Express

Circuit Playground Express

Things used in this project

Hardware components

Software apps and online services

Story

Circuit Playground Express (CPE) and MakeCode

Accelerometer

Buttons

Infrared Sensor (IR)

Light

Microphone

Temperature

Schematics

Pinouts of Circuit Playground Express

Code

MakeCode Example

Credits

SciJoy

Comments

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