It's time to make a brand new instrument! This instrument is inspired by the trumpet but is waaaaayyy cooler. Why? Because you can program it, and it has lights! How can we make an instrument with code and leds? I'm happy you asked! We're able to do all this because of an awesome electronics learning platform by Adafruit called the Circuit Playground Express! It has buttons, leds, a speaker, a tilting tracker (formally called an "accelerometer") and much more!

With your new instrument you'll be able change the pitch and volume by tilting the Circuit Playground Express in various directions. Pretty cool!

In this project you will learn:

  • Beginner programming concepts with MakeCode.
  • How to interact with hardware such as leds, an accelerometer, buttons, and a speaker.
  • Some basic music theory.
  • How to play a brand new instrument!

 

How to Use

Orientation

makecode_trumpet-3303724_640.jpg
photo by congerdesign

To play the Tilt Trumpet, you can hold it just like a Trumpet! Orient the Circuit Playground Express so that your index finger (left or right) lies on button A and your middle finger lies on button B as seen below.

You may hold the Tilt Trumpet how ever you like but this is the orientation I find most comfortable.

Changing Pitch

To start playing a tone, press either of the buttons. The closer button (A) will play a lower tone where as the farther button (B) will play a higher tone.

If you tilt the board away from you while holding either of the buttons, the pitch will increase. If tilted toward you, the pitch will decrease.

Changing Volume

If tilted to the left the volume will increase.

If tilted to the right the volume will decrease.

What you'll need:

1 x Circuit Playground Express
Circuit Playground Express
1 x Micro USB Cable
USB cable - A/MicroB - 3ft
  • Access to a computer (any operating system will do)

Testing it Out

If you'd like to try out the Tilt Trumpet for yourself before we dig into the programming, feel free to download the file below by simply clicking on the button. You should find a file entitled "circuitplayground-Tilt_Trumpet.uf2" in your downloads folder. Skip ahead to the section "Uploading Code" to find out how to upload the file to your Circuit Playground Express.

If you uploaded the file to your Circuit Playground Express, now try testing the Tilt Trumpet out by holding each button down and tilting the board around. Pretty cool right? How does it all work? And how does the board know how to change pitches and NeoPixel colors? We'll dive into all that right away.

Let's get started!

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MakeCode logo. Source: Microsoft.

What is MakeCode?

MakeCode is a web based code editor for physical computing made by Microsoft.

What does that mean for you? It means you can program your Circuit Playground Express to do almost anything you can dream up right from a website! You can code with blocks similar to the language Scratch, or you can do more advanced coding with Javascript. We'll be sticking to the block-based programming for this project.

More on MakeCode for Adafruit boards here.

Above is a simple example of what can be done in MakeCode. In the example, every half second (500ms) the board's NeoPixel leds change from red to blue then back to red etc. forever.

Head over to https://makecode.adafruit.com/ and create a new project.

Once you click "New Project" your screen should look something like this.

This is your code editor. What ever we code on the right will affect the Circuit Playground Express board on the left! That way we know our project should work before we upload the code to the board.

To begin let's create the basic functionality for button A. Such that when button A is pressed, we play a pitch out of the speaker that corresponds to how far forward or back we are tilting the device.

To do this we need a "conditional statement" for when button A is pressed. We want to say "If button A is pressed, then play a pitch".

  • Grab an "if" statement from the "logic" tab and drag it inside the forever loop.
  • Next grab a "button A is pressed" statement from the "input" tab and replace it with the "true" element next that's part of the if statement.

Next we will define what we want to happen when button A is pressed. To start, let's say when button A is pressed, a middle C will sound.

  • Go to the music tab and grab a "play tone at middle C for 1/2 a beat".
  • Place it inside of the if statement.

Now we can test out what we have so far by pressing button A on the virtual Circuit Playground Express on the left. Try pressing button A and see what happens (make sure your computer volume is on).

Neato!

Now it's time to program the initial tilt functionality!

The board's accelerometer allows us to sense which way the board is tilted.

What is an accelerometer? Most smart phones have accelerometers. They are used for example every time you turn your phone sideways or upright again. The screen adjusts accordingly because it knows which orientation it's experiencing, thanks to the accelerometer.

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Smart phone accelerometer orientation. Source: Engadget

The way the accelerometer on the board works is that it can sense the amount of "gravity" it feels in 3 different axes.

makecode_image_ADZiECQJoA.jpeg
Circuit Playground Express Accelerometer

The three axes I'm talking about are the x, y, and z axis shown on the board above.

The gravity on the x axis is what we'll use to determine the pitch. The gravity on the y axis is what we'll use to determine volume.

makecode_image_KOv1kZYtbA.jpeg
3 dimensional axis. Source: intmath.com

So how do we measure gravity? In Gs!

1G is equivalent to Earth's gravitational pull at a resting point.

In this case we'll actually be using mgs which are milligravities! Meaning 1000mg is 1G. So if the board is tilted all the way in the x or y direction we will assume the accelerometer is feeling close to 1000mg or 1G in that direction. In this case we won't worry about the z axis which feels a constant 1G when the board is at rest as the z axis is perpendicular to gravity.

Now, with the accelerometer on the board, we can use gravity or mgs as an input to determine each pitch.

Learn more about the accelerometer on the Circuit Playground Express here.

Now that we know what values of gravity we may want to try with the board, we need to figure out how many and which pitches we want from 1 G (The board tilted all the way forwards) to -1G (The board tilted all the way backwards).

In this project, I decided to make the pitches all in the C major scale or "key signature" however the beauty with programming is you may change the pitches to what ever key or crazy pattern you'd like.

The notes in the C major scale are quite simply all the white notes from C up to B. More about the C major scale and key signature here.

makecode_image.png
One octave on the piano. Source: the howtoreadmusic blog

Let's say we want 8 pitches, the notes C, D, E, F, G, A, B, then the high C.

With 8 pitches we will put 4 in the negative x direction (tilting back) and 4 in the positive x direction (tilting forward).

Rather than starting at -1000 mg for the low C I decided to start at -775mg because it gave more control and room to play without really having to twist my arm to play the lowest or highest notes.

Starting at -775mg for the low C and ending at 775mg for the high C will be the range we will program all the other pitches in between. Each pitch will have a range of 225mg.

With that said let's map out the logic for when we want each pitch to be played:

Tilted backward:

  • Low C will be played when acceleration in the x direction is less than -775mg (Tilted all the way backward)
  • Low D will be played when acceleration in the x direction is greater than -775mg but less than -550mg
  • Low E will be played when acceleration in the x direction is greater than -550mg but less than -225mg
  • Low F will be played when acceleration in the x direction is greater than -225mg but less than 0mg

Tilted forward:

  • Low G will be played when acceleration in the x direction is greater than 0mg but less than 225mg
  • Low A will be played when acceleration in the x direction is greater than 225mg but less than 550mg
  • Low B will be played when acceleration in the x direction is greater than 550mg but less than 775mg
  • High C will be played acceleration in the x direction is more than 775mg (Tilted all the way forward)

Let's start with the low C. As defined in the previous section, "Low C will be played when acceleration in the x direction is less than -775mg"

Again there are two conditions that must be met for the low C to be played. The first is that button A must be pressed. The second is that the acceleration in the x direction is less than -775mg. To do this we must add a second if statement that checks for accelerometer value within the first that checked for button A being pressed.

  • Add an if statement within the first if statement we made.

Next we need a comparison operator to check the condition of the accelerometer value.

  • Go to the logic tab and grab a comparison operator and drag it where "true" is next to the if statement.

We now need to determine what we are comparing. We want to compare the acceleration in the x direction to -775mg. If it is lower than -775mg the low C should be played.

  • Go to the input tab and grab an "acceleration (mg)" statement.
  • Make sure the axis is set to x.
  • Change the operator sign to be less than ("<")
  • Then change the value in the white oval to be -775

Now that our logic is sound, we can go ahead and tell the program to play a low C if all the above conditions are met.

  • Add the Middle C from the music tab then click on the "Middle C" white oval and select the lower C on the piano.

We will program the next note to play between -775mg and -550mg.

  • Click the plus sign on the bottom of the inside if statement. An "else" should have popped in as part of the block.
  • Now click the plus sign again. You will see an "else if then" pop into the block.

The "else if" part of the statement will allow us to check for the other desired accelerometer positions.

Because we need to check if the accelerometer is between two values, we need an extra statement that will do this for us.

  • Go to the logic tab and grab the first "boolean" operator and drag it in the empty slot next to the else if statement.
  • Since we want the accelerometer value to be greater than -775mg and less than -550mg, choose the "and" operator.
  • To create the two comparisons you can copy and paste the same one we made from above and change the values to be > -775mg and < -550mg.
  • Then, drag another music tone into the new condition and change it to low D.

Rinse and Repeat

Now that you know how to create new conditional statements within the inner if statement, continue the process for the rest of the pitches and accelerometer values.

Remember you can copy and paste entire elements and groups of elements!

Your code should look like this when all said and done... Pretty!

Changing the "Tone" of Your Tilt Trumpet

You can change the character of the tone of the sound by changing the length of the beat. My settings play each pitch for an 1/8th of a beat repeatedly but you can change yours to whatever you wish. This code is inside a forever loop and thus is continuously looping through the code. Thus it will continue playing that same 1/8th or 1/2 or what ever chosen length of a beat as it gets looped, simulating a constant flow of sound.

Now that we have the lower pitches worked out with button A, let's make the upper pitches with button B.

We need to add an else if statement to our outer if statement to check for button B presses.

  • Click the plus sign that the bottom of the outer if statement twice to make the "else if, then" statement appear.
  • Now copy and paste just the "button A is pressed" statement from above and drag it into the else if condition.
  • Click the drop down and change it to button B.

Most of the code for button B is going to be the same as the code we wrote for button A. The pitches will just be one octave higher.

  • Copy and paste the entire block of code of the inner if statement we made earlier.
  • Now drag it inside the button B if statement.
  • Now let's change the pitches to be one octave higher. As mentioned earlier you can click on each note and change it by clicking your desired note on the piano.

Most musicians have a way to control the volume of their instrument. Whether it's a trumpet and the instrumentalist simply uses more air at a faster speed to play louder or a piano player that strikes the keys with more intensity, musicians need some way to play louder and quieter.

We just programmed the board to change pitch based on how far forward or backward it is tilted on the x axis. Can we use the y axis and tilt the board left and right to do something else? How about changing volume?!

Let's add another if statement after the first massive one we just programmed. This new if statement code block is separate from the previous one but still lies within the overall forever loop.

  • Grab an if statement and drag it below our first one. 

This if statement block will check the accelerometer value of the y axis to dictate volume.

I wanted to have more variability in volume control compared to pitch control so I decided to make 11 different volume levels mostly because of the simpler math that splitting the mgs into gave me.

Here is a map of the logic we will use to program the volume on the y axis of the accelerometer.

Tilting to the left:

  • If acceleration is less than -900 mgs, play the loudest volume at 220 (Tilted all the way to the left)
  • If acceleration is in between -900 and -700 mgs play volume at 200
  • If acceleration is in between -700 and -500 mgs play volume at 180
  • If acceleration is in between -500 and -300 mgs play volume at 160
  • If acceleration is in between -300 and -100 mgs play volume at 140

Not tilted (level)

  • If acceleration is in between -100 and 100 mgs play volume at 120

Tilting to the right:

  • If acceleration is in between 100 and 300 mgs play volume at 100
  • If acceleration is in between 300 and 500 mgs play volume at 80
  • If acceleration is in between 500 and 700 mgs play volume at 60
  • If acceleration is in between 700 and 900 mgs play volume at 40
  • If acceleration is greater than 900 mgs play volume at 20 (Tilted all the way to the right)

Programming the Volume

  • Let's start by grabbing another comparison operator from the logic tab.
  • Go ahead and place that in the new if statement we created.
  • Now go to the input tab and take an acceleration input to place into the first part of the comparison. Next make sure the comparison is less than (<).
  • Lastly change the value of the white bubble to be 900.

Next we'll set the volume for this condition.

  • Go to the music tab and grab a "set volume" element.
  • Drag it inside the new if statement and set the volume to 220.
  • Now let's click the plus sign twice like before so we can continue to build out this if statement.

For the next condition it will be much faster to copy and paste a condition we wrote earlier for the first if statement.

  • Once you copy, paste and drag the new conditional statement into the new if else statement, make sure you change the values to reflect the new statement.
  • Then copy and paste a "set volume" element, throw it in the new if else and change it to 200.
  • Like before, repeat this process until all the conditions are accounted for.

The NeoPixel leds on the Circuit Playground Express are too great not to be used in my opinion so I decided to integrate them into the instrument giving the player super cool performance lighting.

I chose a rainbow ordered color scheme and decided to set the brightness of the leds based on the loudness of the note.

In my code I have a different color that is shown for each pitch.

  • To set or change the color of the leds, go to the light tab and grab a "set all pixels to" element.
  • Now drag it up to the button A if statement and inside of the first inner if else, under the lowest note.
  • Now choose your desired color.
  • Copy, paste and repeat until all pitches on buttons A and B have colors assigned.
makecode_screen_shot_2018-04-08_at_1_23_45_am_xLqWWgYRtN.jpeg
Button A colors assigned.
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Make sure you do choose colors for button B as well.

To set the brightness let's utilize the last if statement we wrote to control volume. We can set lighting levels where we set sound levels so they match.

  • Go to the light tab, grab a set brightness element and place it under the first set volume element in the volume if statement.
  • Set the brightness to 220.
  • Repeat for all volume levels.

One last thing we need to take care of before finishing up with the code is making sure the NeoPixels turn off if neither button is bring pressed.

  • To ensure this happens, we place a "set all NeoPixels" element in the outside "else" part of the pitch if statement.
  • Change the color to black.

All done with code!

 

Here's the full project you can play with from MakeCode's platform.

Now that we have the code for the project, we need to upload it to the Circuit Playground Express.

Let's name our file and download it.

  • Choose a name at the bottom of the page.
  • Then click the pink download button.

A pop up like this should come on your screen after clicking the download button.

Follow the directions and connect your Circuit Playground Express to your computer via the usb cable. Click the reset button once to go into programming mode.

If you previously have CircuitPython running on your board, you may need to press the reset button twice.

Next, look for the file in your downloads folder and drag it onto your CPLAYBOOT drive that should have showed up when you plugged in your board and entered programming mode.

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Drag the file onto the CPLAYBOOT drive.

You should now see the CPLAYBOOT disappear.

Go ahead and try out your new Tilt Trumpet!

If you are having issues getting things to work check out this extended guide here.

I power my Circuit Playground with a micro USB cable and external battery.

USB cable - 6" A/MicroB
This here is your standard A-microB USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your NETduino, Arduino Leonardo, Raspberry Pi (among other things).
$2.95
In Stock
USB Battery Pack - 2200 mAh Capacity - 5V 1A Output
A smaller-sized rechargeable battery pack for your Raspberry Pi or Raspberry...
Out of Stock

However, if you want to make the project more portable, you can grab a lithium rechargeable battery and a switch that will fit nicely inside the case. Directions on that here.

As mentioned earlier, I chose to program my Tilt Trumpet in the key of C. Meaning all pitches that are sounded are in the C major scale, which includes the notes, C, D, E, F, G, A and B. My reasoning was mostly for simplicity sake as on a piano, in order to play a solo within the key of C, as long as you hit any white note, you are playing in the key of C major and for the most part it will sound pretty good.

In the very beginning of this tutorial, I shared the below video of me playing the Tilt Trumpet over some synth chords and a drum recording of my friend John.

In order for the notes of the Tilt Trumpet to be in the "right" key, the synth chords must be in C major right?

Surprisingly, there is one other key I could play the chords in to make the Tilt Trumpet create "nice" sounding notes over the chords.

Can you notice the quality of the chords? Do they sound positive and uplifting or dark and spooky?

If they were positive and uplifting, that would suggest they were in a major key, but they seem more dark and spooky to me.

That is because they are in a minor key.

The key of the chords I am playing is actually A minor.

So how can the C major scale notes from the Tilt Trumpet sound so "good" over A minor chords?

Fun fact: every major key has a relative minor key.

makecode_circle-of-fifths.gif
Relative Minor Chart. Source: piano-keyboard-guide.com

In the chart above, you can see every major scale and its relative minor.

The 6th note of any major key's scale is the relative minor key.

In the C major scale, the sixth note is A, (CDEFGAB).

The scale of a relative minor is the same as its relative major's but starting on the 1st note of the relative minor.

So starting on A, the A minor scale is (ABCDEFG)

Try playing these two different scales virtual piano website here.

Find a piano note reference guide below.

Did you notice how different the scales felt but that the notes were exactly the same? Just by starting on a different pitch, we get two vastly different perceptions of the same notes. Pretty cool stuff!

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One Octave on the Piano. Source: the howtoreadmusic blog
Disclaimer: Music is subjective and one person's version of a melody or solo sounding "nice" or "right" is different from another's. I'm going off the rules of basic music theory here and am not an expert so there could be many nuances that I am not touching on. I apologize if I am not completely accurate! 

I hope you enjoyed this project and that you learned a few things about coding and music theory! You are way closer to being able to code in more complex languages where you will be able to have more control. For now, I would say MakeCode is pretty useful for starting out!

So what other features can you dream up for the Tilt Trumpet with the Circuit Playground Express sensors?

Now that you upped your coding skills, it's time to start honing your Tilt Trumpet skills!

Time to practice!

This guide was first published on Apr 11, 2018. It was last updated on Apr 11, 2018.