# BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Overview ![](https://cdn-learn.adafruit.com/assets/assets/000/088/038/medium800/feather_edited_P1220373.jpg?1580840079) In this project, Bluetooth Low Energy (BLE) is used to have a **Feather nRF52840** and **Circuit Playground Bluefruit** communicate with each other to create a wireless 8-bit music synthesizer. The Feather has 12 buttons attached to its I/O pins. Each time a button is pressed, it sends a BLE packet to the Circuit Playground Bluefruit. When the Circuit Playground Bluefruit receives those packets, it swirls its on-board NeoPixels in a specific color and plays a tone. ### The Bluefruit Playground App This project was inspired by the tone example in the **Bluefruit Playground App**. With the app, you may connect your Circuit Playground Bluefruit board to your iOS device and then play with a series of examples, each with a user interface to allowing control of the Circuit Playground Bluefruit sensors. One of those examples has a piano keyboard in the app and when the keys are pressed, they cause a tone to play from the Circuit Playground Bluefruit. I thought it would be cool to recreate this concept with hardware. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/036/medium800/feather_edited_P1220378.jpg?1580840062) [Check out this Learn Guide on the Bluefruit Playground App](https://learn.adafruit.com/bluefruit-playground-app) ## Project Video https://youtu.be/mBScFbHKeEY ## Parts ### Adafruit Feather nRF52840 Express [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062) The **Adafruit Feather nRF52840 Express** is the new Feather family member with Bluetooth® Low Energy and _native USB support_ featuring the nRF52840!  It's our take on an 'all-in-one' Arduino-compatible + Bluetooth® Low Energy with built-in USB... In Stock [Buy Now](https://www.adafruit.com/product/4062) [Related Guides to the Product](https://learn.adafruit.com/products/4062/guides) ![Angled shot of a Adafruit Feather nRF52840 Express. ](https://cdn-shop.adafruit.com/640x480/4062-02.jpg) ### Circuit Playground Bluefruit - Bluetooth® Low Energy [Circuit Playground Bluefruit - Bluetooth® Low Energy](https://www.adafruit.com/product/4333) **Circuit Playground Bluefruit** is our third board in the Circuit Playground series, another step towards a perfect introduction to electronics and programming. We've taken the popular Circuit Playground Express and made it even better! Now the main chip is an nRF52840... Out of Stock [Buy Now](https://www.adafruit.com/product/4333) [Related Guides to the Product](https://learn.adafruit.com/products/4333/guides) ![shot of a Black woman's neon-green manicured hand holding up a Circuit Playground Bluefruit glowing rainbow LEDs.](https://cdn-shop.adafruit.com/640x480/4333-11.jpg) ### Adafruit STEMMA Speaker - Plug and Play Audio Amplifier [Adafruit STEMMA Speaker - Plug and Play Audio Amplifier](https://www.adafruit.com/product/3885) Hey, have you heard the good news? With Adafruit STEMMA boards you can easily and safely plug sensors and devices together, like this **Adafruit STEMMA Speaker - Plug and Play Audio Amplifier**. Like the name implies, it's got a class D audio amplifier on board, and our... In Stock [Buy Now](https://www.adafruit.com/product/3885) [Related Guides to the Product](https://learn.adafruit.com/products/3885/guides) ![Top view of a black speaker breakout board connected to a round microcontroller via alligator clips. A music note animation emits from the speaker.](https://cdn-shop.adafruit.com/product-videos/640x480/3885-05.jpg) ### Colorful Round Tactile Button Switch Assortment - 15 pack [Colorful Round Tactile Button Switch Assortment - 15 pack](https://www.adafruit.com/product/1009) Little clicky switches are standard input "buttons" on electronic projects. These work best in a PCB but [can be used on a solderless breadboard as shown in this tutorial](http://www.ladyada.net/learn/arduino/lesson5.html). The pins are normally open (disconnected) and... In Stock [Buy Now](https://www.adafruit.com/product/1009) [Related Guides to the Product](https://learn.adafruit.com/products/1009/guides) ![Top-down shot of 15 colorful round tactile button switches in green, yellow, red, blue, and white.](https://cdn-shop.adafruit.com/640x480/1009-07.jpg) ### 3 x AAA Battery Holder with On/Off Switch and 2-Pin JST [3 x AAA Battery Holder with On/Off Switch and 2-Pin JST](https://www.adafruit.com/product/727) This battery holder connects 3 AAA batteries together in series for powering all kinds of projects. We spec'd these out because the box is slim, and 3 AAA's add up to about 3.3-4.5V, a very similar range to Lithium Ion/polymer (Li-Ion) batteries and have an on-off switch. That makes... In Stock [Buy Now](https://www.adafruit.com/product/727) [Related Guides to the Product](https://learn.adafruit.com/products/727/guides) ![Front angled shot of 3 x AAA battery holder with on-off switch and 2-pin JST PH connector.](https://cdn-shop.adafruit.com/640x480/727-07.jpg) ### Part: Perfboard Plates quantity: 1 Bakelite, universal, pack of 10 [Perfboard Plates](https://www.adafruit.com/product/2670) ### Part: Slide Switch quantity: 1 SPDT - breadboard friendly [Slide Switch](https://www.adafruit.com/product/805) ### Part: Short Female Headers for Feather quantity: 1 One 12-pin and one 16-pin [Short Female Headers for Feather](https://www.adafruit.com/product/2940) ## Helpful Tools ### Super Scissors [Super Scissors](https://www.adafruit.com/product/1599) Save your scissors! Instead of using your nice shears (and dulling them) or wire cutters (not right for the job) - use these super scissors. They're meant for engineering/maker cutting jobs such as cutting plastic, leather, copper sheet/wire, even coaxial & ribbon cables. There's a... In Stock [Buy Now](https://www.adafruit.com/product/1599) [Related Guides to the Product](https://learn.adafruit.com/products/1599/guides) ![Very strong looking scissors with comfy grip](https://cdn-shop.adafruit.com/640x480/1599-09.jpg) # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Electronics Overall, the electronics for this project are fairly straightforward. Most of the hard work will be happening in the code. ## Feather nRF52840 Keyboard The **Feather** is acting as the **keyboard** , it has 12 buttons hooked up to its I/O pins. The Feather has just enough pins, with a few extra to spare. The buttons will represent the notes on a keyboard chromatically: C, C#, D, D#, E, F, F#, G, G#, A, A# and B. We'll also add an on/off switch by having a switch between the Feather **GND** and **EN** pins. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/039/medium800/ble_feather_synth_bb.png?1580840155) ## Circuit Playground Bluefruit Amp The **Circuit Playground Bluefruit** is our speaker, or **amplifier** , for our 8-bit synth. It does have an onboard speaker that we can use, but for maximum loudness we're also going to add a **STEMMA Speaker**. The **STEMMA Speaker** has three connections that need to be made: **POWER** , **GND** and **SIGNAL**. We'll add an on/off switch by using a **3x AAA battery pack** that plugs into the **JST battery connector** with a built-in on/off switch. This will be able to fit inside our 3D printed case. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/040/medium800/feather_ble_cpb_speaker_bb.png?1580840168) # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Soldering - Feather Keyboard ## PCB vs. Perfboard A PCB was created for this project and the Eagle files are available below. If PCBs aren't your thing though, don't worry- there are instructions below on how to solder up a version using perfboard. Since the circuit is straightforward, either option is great. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/054/medium800/feather_edited_P1220392.jpg?1580843193) ## PCB For the PCB assembly, place the buttons into their spots on the board and solder each of their four points on the back. Then, solder some **Feather headers** into the header holes. And with that you have a fully assembled board. You can download the Eagle files for the PCB below. [bleFeatherSynth.zip](https://cdn-learn.adafruit.com/assets/assets/000/088/056/original/bleFeatherSynth.zip?1580843871) The PCB was designed with the round tactile button switches in mind. They're also used for perfboard version and the 3D printed piano keys are sized for their round toppers. ### Colorful Round Tactile Button Switch Assortment - 15 pack [Colorful Round Tactile Button Switch Assortment - 15 pack](https://www.adafruit.com/product/1009) Little clicky switches are standard input "buttons" on electronic projects. These work best in a PCB but [can be used on a solderless breadboard as shown in this tutorial](http://www.ladyada.net/learn/arduino/lesson5.html). The pins are normally open (disconnected) and... In Stock [Buy Now](https://www.adafruit.com/product/1009) [Related Guides to the Product](https://learn.adafruit.com/products/1009/guides) ![Top-down shot of 15 colorful round tactile button switches in green, yellow, red, blue, and white.](https://cdn-shop.adafruit.com/640x480/1009-07.jpg) ## Perfboard For the perfboard assembly, you need two pieces to start. Begin by placing 6 of the buttons on the first piece. The buttons should be placed 5 holes apart to have the spacing work for the 3D printed keys. Cut pieces of wire for the **ground** and **input pins** for each button. The ground connections will daisy chain between each button, so they should be just long enough to reach the next button. The input wires will need to be long enough to reach where the **Feather** will eventually live on the far right side of the assembly. Repeat this process for the second piece of perfboard for five of the buttons. ![](https://cdn-learn.adafruit.com/assets/assets/000/087/996/medium800/feather_IMG_8944.jpg?1580747835) ![](https://cdn-learn.adafruit.com/assets/assets/000/087/997/medium800/feather_IMG_8977.jpg?1580747855) To make the connections on this type of perfboard, you'll need to bridge the individual solder points. For example, the input wire for the first button should have some solder that connects the two points. ![](https://cdn-learn.adafruit.com/assets/assets/000/087/998/medium800/feather_IMG_8978.jpg?1580747878) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/057/medium800/feather_IMG_8977_cuts.jpg?1580844089 cut lines in red) Next, cut the right edge off on the first piece and left edge off on the second piece. This will allow placement of a button, which will eventually be F#, in the middle. Place this button on the edge of the first piece, so that it's hanging off. Then run a short piece of wire to connect it to the second piece. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/058/medium800/feather_edited_P1220393.jpg?1580844125) Then, we're going to cut another section: the last column of five rows on the right hand side of the second piece. Then solder on Feather headers as shown in the picture. ![](https://cdn-learn.adafruit.com/assets/assets/000/087/999/medium800/feather_IMG_9016.jpg?1580747908) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/060/medium800/feather_edited_P1220395.jpg?1580844186) With the headers in place, connect the button wires to the Feather. Run the **input wires** to the appropriate **I/O pin** and then bridge the connections. Do the same with the **ground** signal. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/059/medium800/feather_edited_P1220394.jpg?1580844173) Finally, to add an **on/off switch**. Place it on the board and then run a wire from **GND** to one lead on the switch and then a wire from **EN** to the middle lead. Connecting **EN** to **GND** allows for built-in on/off control. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/061/medium800/feather_edited_P1220388.jpg?1580844210) And there you have a perfboard equivalent to the PCB. # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Soldering - Circuit Playground Bluefruit To connect the **STEMMA Speaker** , use a STEMMA connector cable to plug into the STEMMA connector on the speaker's board. Then take those three wires and solder them to the Circuit Playground Bluefruit pins. **POWER** will be soldered to **3.3V** , **GND** will be soldered to **GND** and **SIGNAL** will be soldering to **AUDIO (A0)**. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/041/medium800/feather_editedP1220381.jpg?1580840302) # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## CircuitPython Code Setup Take your Feather nRF52840 and plug it into your computer via a known good data + power USB cable. Have your Circuit Playground Bluefruit handy as you'll be performing most of the same steps for each. Your operating system will show a drive named **CIRCUITPY** when a board is plugged in. If you get a drive named **CPLAYBTBOOT** or **FTHR840BOOT** , you'll likely need to install CircuitPython. This is easy, see the steps below to do this, get library files, and copy the code to each board. ## Feather nRF52840 CircuitPython Setup First, make sure you're running the most recent version of CircuitPython for the Feather nRF52840. [Click to read on installing CircuitPython on the Feather nRF52840](https://learn.adafruit.com/introducing-the-adafruit-nrf52840-feather/circuitpython) ## Circuit Playground Bluefruit Circuit Python Setup Just like with the Feather, make sure you're running the most recent version of CircuitPython for the Circuit Playground Bluefruit. [Click to read on installing CircuitPython on the Circuit Playground Bluefruit](https://learn.adafruit.com/adafruit-circuit-playground-bluefruit) ## Download the Code from GitHub To use with CircuitPython, you need to first install a few libraries, into the lib folder on your **CIRCUITPY** drive. Then you need to update **code.py** with the example script. Thankfully, we can do this in one go. In the example below, click the **Download Project Bundle** button below to download the necessary libraries and the **code.py** file in a zip file. Extract the contents of the zip file, open the directory **BLE\_Synth**** /cpb\_amp\_code **for the Circuit Playground Bluefruit and** BLE\_Synth/feather\_keyboard\_code **for the Feather nRF52840 and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your respective** CIRCUITPY** drives. Your **CIRCUITPY** drive on the  **Circuit Playground Bluefruit**  should now look similar to the following image: ![CIRCUITPY](https://adafruit.github.io/Adafruit_Learning_System_Guides/BLE_Synth_cpb_amp_code.png ) Your **CIRCUITPY** drive on the **Feather nRF52840** should now look similar to the following image: ![CIRCUITPY](https://adafruit.github.io/Adafruit_Learning_System_Guides/BLE_Synth_feather_keyboard_code.png ) ### Circuit Playground Bluefruit BLE Synth Code https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/BLE_Synth/cpb_amp_code/code.py ### Feather nRF52840 BLE Synth Code https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/BLE_Synth/feather_keyboard_code/code.py # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## CircuitPython Code Walkthrough Both the **Feather nrF52840** and **Circuit Playground Bluefruit** are running their own **code.py** file. In this case, the Feather's **code.py** file could be considered the A file and the Circuit Playground Bluefruit's **code.py** file could be considered the B file. The Feather is in charge because the Circuit Playground Bluefruit is waiting for the button inputs to be able to do anything. [Check out this Learn Guide for more info on BLE communication between boards](https://learn.adafruit.com/circuit-playground-bluefruit-neopixel-animation-and-color-remote-control/overview) The Feather's code begins by setting up its **digital inputs** and **outputs**. The **on-board blue LED** will be used to indicate whether the boards have connected with each other via **BLE**. The rest of the **pins** are setup to be **button inputs** and are placed into the **array** `switch_array[]`. ```python blue_led = digitalio.DigitalInOut(board.BLUE_LED) blue_led.direction = digitalio.Direction.OUTPUT switch_pins = [board.D5, board.D6, board.D9, board.D10, board.D11, board.D12, board.D13, board.A0, board.A1, board.A2, board.A3, board.A4] switch_array = [] for pin in switch_pins: switch_pin = digitalio.DigitalInOut(pin) switch_pin.direction = digitalio.Direction.INPUT switch_pin.pull = digitalio.Pull.UP switch_array.append(switch_pin) ``` Next, **state machines** are setup for the **button debouncing**. These states are then put into the array `switches_pressed[]`. ```python switch1_pressed = False switch2_pressed = False switch3_pressed = False switch4_pressed = False switch5_pressed = False switch6_pressed = False switch7_pressed = False switch8_pressed = False switch9_pressed = False switch10_pressed = False switch11_pressed = False switch12_pressed = False switches_pressed = [switch1_pressed, switch2_pressed, switch3_pressed, switch4_pressed, switch5_pressed, switch6_pressed, switch7_pressed, switch8_pressed, switch9_pressed, switch10_pressed, switch11_pressed, switch12_pressed] ``` Going to the **Circuit Playground Bluefruit** , at the beginning of its **code.py** file, there is some setup for the **NeoPixels Animations library**. The **Comet** animation is being used to get a nice swirly effect each time a note is played. ```python COMET_SPEED = 0.04 # Lower numbers increase the animation speed CPB_COMET_TAIL_LENGTH = 5 # The length of the comet on the Circuit Playground Bluefruit CPB_COMET_BOUNCE = False # Set to True to make the comet "bounce" the opposite direction on CPB animations = AnimationSequence( AnimationGroup( Comet(cpb.pixels, COMET_SPEED, off, tail_length=CPB_COMET_TAIL_LENGTH, bounce=CPB_COMET_BOUNCE))) ``` [Check out this Learn Guide on the Animation library](https://learn.adafruit.com/circuit-playground-bluefruit-neopixel-animation-and-color-remote-control/neopixel-animator-code) Speaking of notes, the tones that will be played through the **STEMMA Speaker** when the buttons are pressed are then setup. Variables matching the note and octave are set to match the correct **frequencies of the notes**. These are then put into an array called `note[]`. ```python C4 = 261.63 Csharp4 = 277.18 D4 = 293.66 Dsharp4 = 311.13 E4 = 329.63 F4 = 349.23 Fsharp4 = 369.99 G4 = 392 Gsharp4 = 415.3 A4 = 440 Asharp4 = 466.16 B4 = 493.88 note = [C4, Csharp4, D4, Dsharp4, E4, F4, Fsharp4, G4, Gsharp4, A4, Asharp4, B4] ``` This next portion has a bit of synergy between both **code.py** files. Previously it was mentioned that the Feather is sending **BLE packets** to the Circuit Playground Bluefruit, but what type? C **olor packets**. This means that the CPB has to know which colors to be listening for. As a result, both the Feather and CPB have identical colors defined. These are then put into an array in the same order. It so happens that both files call this array `color[]`. The colors being used are also from the **Animations** library. They're predefined in that library so that we don't have to worry about dialing in the exact RGB values. ```python color_C = color.RED color_Csharp = color.ORANGE color_D = color.YELLOW color_Dsharp = color.GREEN color_E = color.TEAL color_F = color.CYAN color_Fsharp = color.BLUE color_G = color.PURPLE color_Gsharp = color.MAGENTA color_A = color.GOLD color_Asharp = color.PINK color_B = color.WHITE color = [color_C, color_Csharp, color_D, color_Dsharp, color_E, color_F, color_Fsharp, color_G, color_Gsharp, color_A, color_Asharp, color_B] ``` The next portions for both files are some **BLE** setup and the beginning of the **loop**. At the start of the loop, BLE connections are made between the two boards and if the connection is present then they can proceed to the synth portions of the loop. ```python # CPB BLE portion ble = BLERadio() uart = UARTService() advertisement = ProvideServicesAdvertisement(uart) while True: ble.start_advertising(advertisement) # Start advertising. was_connected = False while not was_connected or ble.connected: if ble.connected: # If BLE is connected... was_connected = True animations.animate() if uart.in_waiting: # Check to see if any data is available from the Remote Control. try: packet = Packet.from_stream(uart) # Create the packet object. except ValueError: continue ``` ```python # Feather BLE portion def send_packet(uart_connection_name, packet): """Returns False if no longer connected.""" try: uart_connection_name[UARTService].write(packet.to_bytes()) except: # pylint: disable=bare-except try: uart_connection_name.disconnect() except: # pylint: disable=bare-except pass return False return True ble = BLERadio() uart_connection = None if ble.connected: for connection in ble.connections: if UARTService in connection: uart_connection = connection break while True: blue_led.value = False if not uart_connection or not uart_connection.connected: # If not connected... print("Scanning...") for adv in ble.start_scan(ProvideServicesAdvertisement, timeout=5): # Scan... if UARTService in adv.services: # If UARTService found... print("Found a UARTService advertisement.") blue_led.value = True uart_connection = ble.connect(adv) # Create a UART connection... break # Stop scanning whether or not we are connected. ble.stop_scan() # And stop scanning. ``` For the Feather, there is a `for` statement that iterates through the `switch_array`, which holds the button pins. It defines the indexed position as `i`. Then `i` can be used to also track the debounce state and the **color** that is going to be sent as a color packet. All of these arrays have 12 indexes, one for each note that being used. This way, the indexes can easily be called out as needed from each array all at once without too many lines of code. ```python while uart_connection and uart_connection.connected: for switch_pin in switch_array: i = switch_array.index(switch_pin) switches_pressed_state = switches_pressed[i] colors = color[i] ``` Then there's a check to see if a button has been released with an `if` statement. You'll see that if it has, that a button packet is sent. You'll see why this is included when you see the CPB's loop in a moment. ```python if switch_pin.value and switches_pressed_state: # On button release... print("button off") if not send_packet(uart_connection, # ColorPacket(colors)): ButtonPacket(ButtonPacket.RIGHT, pressed=True)): uart_connection = None continue switches_pressed[i] = False # Set to False. time.sleep(0.05) ``` After that though, there's a check to see if a button has been pressed. If it has, then a color packet is sent. The color depends on the indexed color that matches the indexed button pin. ```python if not switch_pin.value and not switches_pressed_state: # If button A pressed... if not send_packet(uart_connection, ColorPacket(colors)): uart_connection = None continue switches_pressed[i] = True # Set to True. time.sleep(0.05) # Debounce. ``` And that is how packets are being sent to the Circuit Playground Bluefruit. Now let's see what the Circuit Playground Bluefruit is doing when it receives those packets. For the Circuit Playground Bluefruit, there is an **if** statement that checks if a color packet is being received. This is followed by a `for` statement that iterates through the `color` and `note` arrays. ```python if isinstance(packet, ColorPacket): # If the packet is color packet... for i in range(12): colors = color[i] notes = note[i] ``` Then there's an **if** statement that checks to see if the **color packet** being sent by the Feather matches with any of the colors in our colors array. If it does, then a color is sent to the Comet animation and plays the matching tone. `tone` is also being used as a state machine to debounce our CPB. ```python if packet.color == colors and not tone: animations.color = colors cpb.start_tone(notes) tone = True ``` Following that, the loop ends with an `elif` statement. It's checking to see if a `button packet` is coming in. Remember, the Feather was setup to send a button packet once a physical button is released. If the button packet is a `ButtonPacket.RIGHT` (which it will be), then the CPB will stop playing the tone. The animations will continue to animate but with the NeoPixels turned off. `off` was defined earlier to equal `(0, 0, 0)`. If this portion of code wasn't included, then the last tone played would continue playing without stopping. The same would be the case for the NeoPixel animation. ```python elif isinstance(packet, ButtonPacket) and packet.pressed: # If the packet is a button packet... if packet.button == ButtonPacket.RIGHT and tone: # If button B is pressed... tone = False cpb.stop_tone() animations.color = off ``` # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## 3D Printing All of the 3D printing files can be downloaded directly from Thingiverse. Fusion360 files are also available for the individual models if you want to remix them. [Thngiverse Link for all of the .STL files](https://www.thingiverse.com/thing:4144262) ## Keyboard Keys To allow your Feather to live its best life as an 8-bit synth, you need to 3D print some keyboard keys. These keys are sized to snuggly fit over the circular top on these tactile buttons. They also print with no supports and are pretty cute. [Fusion360 File for the Keyboard Keys](https://a360.co/2RX1RaV) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/005/medium800/feather_IMG_8910.jpg?1580748186) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/006/medium800/feather_IMG_8933.jpg?1580748201) ## Circuit Playground Bluefruit Amp Enclosure Since the **Circuit Playground Bluefruit** is acting as the amplifier for the synth, you might as well print a little amp-inspired case. The case is snap-fit and prints without supports. The front of the case has a pattern that make it look like an amp speaker grill. The **CPB** and **STEMMA Speaker** attach to the front via some **M3** and **M2.5** sized holes that allow for screws of the same size. [Fusion360 File for the Amp Case](https://a360.co/36UDKhr) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/055/medium800/feather_fusionSynth.png?1580843407) ## Feather Keyboard Enclosure Options Depending on whether you're using the PCB or perfboard for the Feather portion of the circuit will determine your enclosure. 3D printed options are available for both, along with their Fusion360 files. For the perfboard version, a shallow open box style enclosure is available with lips on the edges that keep it nice and secure. [Fusion360 File for the PerfBoard Keyboard Case](https://a360.co/2tsxDDm) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/051/medium800/feather_edited_P1220403.jpg?1580843005) For the PCB, a base was created that allows for the PCB to sit on top with stand-offs. Much like the amp enclosure, it allows for screws or standoffs to be attached. [Fusion360 File for the PCB Keyboard Base](https://a360.co/2OrLEIO) ![](https://cdn-learn.adafruit.com/assets/assets/000/088/052/medium800/feather_edited_P1220391.jpg?1580843017) # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Assembly ## Circuit Playground Bluefruit Amp On the interior of the lid of the amp case, there are mounting points for both the **Circuit Playground Bluefruit** and **STEMMA Speaker** that allow for some screws to attach the boards. The mounts for the Circuit Playground Bluefruit utilize **M3 sized screws** and the STEMMA Speaker utilizes **M2.5**. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/046/medium800/feather_edited_P1220386.jpg?1580842238) Using M3 screws, attach the Circuit Playground Bluefruit to the amp enclosure lid by lining up the holes with the front of the board facing down. Repeat the same process for the **STEMMA Speaker** with the front of the board again facing down. Attach the **3x AAA battery pack** to the Circuit Playground Bluefruit's **JST battery connector** and then close up the amp. You're ready to amplify some 8-bit tones. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/045/medium800/feather_P1220387.jpg?1580842216) ## Feather Keyboard - PCB The 3D printed base for the PCB allows for screws just like the **Circuit Playground Bluefruit**'s amp enclosure. Using some **M2 standoffs** , twist in the standoffs into the holes on the 3D printed base. Then place the PCB over the standoffs so that the mounting holes line up and attach with some M2 screws. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/047/medium800/feather_edited_P1220385.jpg?1580842420) ## Feather Keyboard - Perfboard The case for the perfboard version of the keyboard allows it to sit snuggly in the shallow box so that all of the electrical connections are protected and structural stability is provided. You can gently press the boards into the box and they should gently click in under the lips on the edges of the box. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/049/medium800/feather_edited_P1220405.jpg?1580842924) # BLE Synth with the Feather nRF52840 and Circuit Playground Bluefruit ## Usage Turn on both the **Circuit Playground Bluefruit** and **Feather nRF52840** keyboard. Once they're connected to each other, the **onboard blue LED** will turn on on the Feather. Then you should be able to press the keyboard buttons and hear your blippy tones blasting out of your CPB amp along with swirling NeoPixels. ![](https://cdn-learn.adafruit.com/assets/assets/000/088/053/medium800/feather_edited_P1220401.jpg?1580843089) ## Featured Products ### Circuit Playground Bluefruit - Bluetooth® Low Energy [Circuit Playground Bluefruit - Bluetooth® Low Energy](https://www.adafruit.com/product/4333) **Circuit Playground Bluefruit** is our third board in the Circuit Playground series, another step towards a perfect introduction to electronics and programming. We've taken the popular Circuit Playground Express and made it even better! Now the main chip is an nRF52840... Out of Stock [Buy Now](https://www.adafruit.com/product/4333) [Related Guides to the Product](https://learn.adafruit.com/products/4333/guides) ### Adafruit Feather nRF52840 Express [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062) The **Adafruit Feather nRF52840 Express** is the new Feather family member with Bluetooth® Low Energy and _native USB support_ featuring the nRF52840!  It's our take on an 'all-in-one' Arduino-compatible + Bluetooth® Low Energy with built-in USB... In Stock [Buy Now](https://www.adafruit.com/product/4062) [Related Guides to the Product](https://learn.adafruit.com/products/4062/guides) ### Adafruit STEMMA Speaker - Plug and Play Audio Amplifier [Adafruit STEMMA Speaker - Plug and Play Audio Amplifier](https://www.adafruit.com/product/3885) Hey, have you heard the good news? With Adafruit STEMMA boards you can easily and safely plug sensors and devices together, like this **Adafruit STEMMA Speaker - Plug and Play Audio Amplifier**. Like the name implies, it's got a class D audio amplifier on board, and our... In Stock [Buy Now](https://www.adafruit.com/product/3885) [Related Guides to the Product](https://learn.adafruit.com/products/3885/guides) ### Colorful Round Tactile Button Switch Assortment - 15 pack [Colorful Round Tactile Button Switch Assortment - 15 pack](https://www.adafruit.com/product/1009) Little clicky switches are standard input "buttons" on electronic projects. These work best in a PCB but [can be used on a solderless breadboard as shown in this tutorial](http://www.ladyada.net/learn/arduino/lesson5.html). The pins are normally open (disconnected) and... In Stock [Buy Now](https://www.adafruit.com/product/1009) [Related Guides to the Product](https://learn.adafruit.com/products/1009/guides) ### 3 x AAA Battery Holder with On/Off Switch and 2-Pin JST [3 x AAA Battery Holder with On/Off Switch and 2-Pin JST](https://www.adafruit.com/product/727) This battery holder connects 3 AAA batteries together in series for powering all kinds of projects. We spec'd these out because the box is slim, and 3 AAA's add up to about 3.3-4.5V, a very similar range to Lithium Ion/polymer (Li-Ion) batteries and have an on-off switch. That makes... In Stock [Buy Now](https://www.adafruit.com/product/727) [Related Guides to the Product](https://learn.adafruit.com/products/727/guides) ### Bakelite Universal Perfboard Plates - Pack of 10 [Bakelite Universal Perfboard Plates - Pack of 10](https://www.adafruit.com/product/2670) Make your next project as you imagine it with prototyping perfboards that can easily be cut with scissors like these **Bakelite Universal Perfboard Plates**! We wanted a perfboard that was both customizable and durable and In Stock [Buy Now](https://www.adafruit.com/product/2670) [Related Guides to the Product](https://learn.adafruit.com/products/2670/guides) ### Breadboard-friendly SPDT Slide Switch [Breadboard-friendly SPDT Slide Switch](https://www.adafruit.com/product/805) These nice switches are perfect for use with breadboard and perfboard projects. They have 0.1" spacing and snap in nicely into a solderless breadboard. They're easy to switch no matter what size fingers you have, but not so easy that they'll get flipped by accident. Work great as... In Stock [Buy Now](https://www.adafruit.com/product/805) [Related Guides to the Product](https://learn.adafruit.com/products/805/guides) ### Short Headers Kit for Feather - 12-pin + 16-pin Female Headers [Short Headers Kit for Feather - 12-pin + 16-pin Female Headers](https://www.adafruit.com/product/2940) These two  **Short**   **Female Headers**  alone are, well, lonely. But pair them with any of our [Feather](https://www.adafruit.com/categories/777) boards and you're in business! These headers are particularly cute and... Out of Stock [Buy Now](https://www.adafruit.com/product/2940) [Related Guides to the Product](https://learn.adafruit.com/products/2940/guides) ## Related Guides - [Introducing the Adafruit nRF52840 Feather](https://learn.adafruit.com/introducing-the-adafruit-nrf52840-feather.md) - [Adafruit Circuit Playground Bluefruit](https://learn.adafruit.com/adafruit-circuit-playground-bluefruit.md) - [Adafruit STEMMA Speaker](https://learn.adafruit.com/adafruit-stemma-speaker.md) - [Snow Globe with Circuit Playground Bluefruit](https://learn.adafruit.com/snow-globe-bluefruit-cpb.md) - [Wirelessly Code your Bluetooth Device with CircuitPython](https://learn.adafruit.com/wirelessly-code-your-bluetooth-device-with-circuitpython.md) - [Circuit Playground TFT Gizmo Snow Globe](https://learn.adafruit.com/circuit-playground-tft-gizmo-snow-globe.md) - [Glowing Bottle Castle and Capacitive Touch Piano](https://learn.adafruit.com/glowing-bottle-castle-and-capacitive-touch-piano.md) - [Multi-tasking with CircuitPython](https://learn.adafruit.com/multi-tasking-with-circuitpython.md) - [LED Emerald with Circuit Playground Bluefruit](https://learn.adafruit.com/led-emerald-with-circuit-playground.md) - [PyLeap Blink Animation](https://learn.adafruit.com/pyleap-device-enabled-blinky.md) - [All the Internet of Things - Episode Three: Services](https://learn.adafruit.com/all-the-internet-of-things-episode-three-services.md) - [Mouse and Keyboard Control Using TinyUSB and BLE](https://learn.adafruit.com/mouse-and-keyboard-control-using-tinyusb-and-ble.md) - [Bluetooth Controlled NeoPixel Lightbox](https://learn.adafruit.com/bluetooth-neopixel-lightbox.md) - [Pulse Oximeter Wireless Data Logger](https://learn.adafruit.com/pulse-oximeter-wireless-data-logger.md) - [Adafruit Circuit Playground TFT Gizmo](https://learn.adafruit.com/adafruit-tft-gizmo.md) - [Bluefruit Luminary Lanterns with Capacitive Touch](https://learn.adafruit.com/bluefruit-luminary-lanterns-with-capacitive-touch.md) - [Circuit Playground-O-Phonor](https://learn.adafruit.com/circuit-playground-o-phonor.md) - [ Memory-saving tips for CircuitPython](https://learn.adafruit.com/memory-saving-tips-for-circuitpython.md)