Posts Tagged ‘ adafruit

Getting started with Adafruit’s Circuit Playground Express


I’ve had a dream of authoring Python code directly on a microcontroller board for a long time.  That became a reality with MicroPython and the pyboard, but I didn’t jump in until my Circuit Playground Express (CPE, below) board from Adafruit showed up recently.

cpe <- CPE in bootloader mode!

This blog post is written as notes for my future-self, when I forget things.  But feel free to follow along reader…

I wrote this guide because despite the fact Adafruit has lot of data out there, it took me hours to sort through it all and figure out what applied, and what didn’t.


Circuit Playground Express Links

Required Hardware

Adafruit Setup Docs

It should be noted that I myself did all of these steps in the below order.  Which makes me wonder, for example, if the drivers & utils I installed during the Arduino section benefited later steps.  Each of these docs is broken out into more detail below The Bootloader section.

  • Circuit Playground Lesson #0 : Arduino Setup
    • This is authored for the “Circuit Playground” (the precursor to the CPE, it is a different thing), but docs still appears to apply.  Probably the best first place to start, but focused on Arduino.
  • MakeCode
    • If you want to try your hand at MakeCode programming on the CPE (Visual blocks, or JavaScript), start here.
  • CircuitPython Setup
    • This is actually a sub-doc for another tutorial, but explains how to setup CircuitPython on the CPE.
    • CircuitPyhon is based on MicroPython, with some differences.

The Bootloader

This CPE bootloader info applies to Arduino, MakeCode, and CircuitPython, so it’s worth calling out here.

Check the Bootloader:

  • Nice (MakeCode) overview here: “Downloading and Flashing“.  It should be noted that Arduino uploads via its own IDE, but you still need a bootloader to receive the data.  More info under “UF2 Bootloader Details“.
  • The first time you plug the CPE in over USB (before any other configuration / software installs), see if the bootloader works.  Press the reset button twice:  All the ring-LEDs should turn green, and D13 should be slowly pulsing.  The image a the top of this post shows this.
  • The issue I had is, the image in the linked docs don’t show the green LEDs:  Since mine were green, and the image of the docs were not, I thought I had a problem.  I did not.
  • IMPORTANT: Once the software is configured correctly (this started happening for me once I configured Arduino), entering bootloader mode should pop open a (Windows) Explorer.  However, the CPE has two different “Windows Explorer modes”:
    • “Bootloader Mode” : Again, all the LEDs should be red, and you should see a few files on it:
      • INDEX.HTM <- web link to the CPE
      • INFO_UF2.TXT  <- tells you about the bootloader
      • CURRENT.UF2  <- the current firware
    • “Program Mode” (I made that term up) : This is the the mode where you can drag & drop your programs onto the board.  This shows up on first time plug-in (usually takes 30 seconds or so for the Explorer window to pop open), or when you press the reset button once.  For example, with CircuitPython installed, I see these files:
      • /lib <- imported bundle libraries
      • <- Main code to execute
      • boot_out.txt
  • Here’s a short video showing how the bootloader works:

Initial Arduino Setup

Based on Circuit Playground Lesson #0 : The links below are entirely from this tutorial, I’m just calling out some of the major points & gotchas.

I got the CPE with the goal of authoring Python code for it.  But based on all the initial documentation I could find, it seemed like Arduino was where one should start.


  • From the docs for your OS: (Windows links below)
  • Add Circuit Playground to Arduino
    • (Obviously) follow all the steps here adding drivers and external packages.
    • This part really confused me for a bit (and Adafruit tech support to the rescue):  Be sure to choose the right board from Tools -> Board Menu.
      • The right board will be under the “Arduino SAMD (…) Boards” section, called “Arduino Circuit Playground Express”.  Any other board with a similar name (like, say, “Circuit Playground”) is wrong.  You’ll know it’s wrong because it won’t upload your sketch correctly.
      • See verbose errors and whatnot from my forum post here.
    • Once you’ve selected the correct COM port, you can then access:
      • Files -> Examples -> Adafruit CircuitPlayground  -> And choose a sketch therein for upload & test.
  • Other Notes:
    • During this process, I couldn’t get Arduino to connect.  After rebooting my machine and restarting the Arduino IDE, it asked me to install additional drivers, which I did.  Around that time things started working correctly.


  • The Arduino “Adafruit Circuit Playground Library Reference” can be found here.

Initial MakeCode Setup

Based on Adafruit’s MakeCode docs:  MakeCode provide a visual programming environment, JavaScript, all programmed in-browser.


There really isn’t an “Install” per-say:  Just browse to : to open the editor.

You can now code in either the “visual blocks”, or JavaScript.

Presuming you can enter “bootloader” mode (discussed in the Arduino section above), once you save a .uf2 file from the MakeCode app, if you drag & drop it onto that open Explorer window, the window should close, and the app immediately run on your CPE.  Pretty slick!

I presume though, that some of those Arduino install steps were required, since my PC wouldn’t recognize the CPE as a USB device properly until then, which would have prevented me from dragging & dropping the .uf2 files onto it.


Initial CircuitPython Setup

From the Adafruit “Circuit Python Setup” docs (for the Metro M0 Express board, not that it matters so much).

This is the whole reason I got this hardware, so far, not disappointed!


  • The above docs do a great job of covering it, but be sure you choose “Circuit Playground Express” options, since the tutorial was written for another board.
  • I flashed the CPE by just drag&dropping the downloaded ‘adafruit-circuitpython-circuitplayground_express-1.0.0.uf2’ (for CircuitPython 1.0, not 2.0, which at the time of this writing just came out and is in beta) file onto the CPE while in bootloader mode.  Note, it did take ‘a while’ for it to update, at one point I thought maybe it had broken.  But then it started working again.
  • I used the CircuitPython Blinky example to upload my first Python module, and it worked!
  • It appears that my current version of CircuitPython is running Python version 3.4.0.

Getting Bundles

  • CircuitPython ‘bundles’ Python libraries together for use on the CPE. Since the space on the CPE is so limited, sometimes you can only include specific compiled libraries with your module.
  • You can access the bundles here @ github: adafruit/adafruit_CircuitPython_Bundle
    • Don’t make the mistake I did:  Just grab (for example) the “” file in the downloads section, not one of the individual libraries above:  They don’t have the ‘lib’ folder you need for transfer to the CPE.

Setting up a Serial REPL Editor

This is a great feature, that allows you to have a live Python interpreter running on the CPE.  This lets you query the board directly in a live coding session, awesome feature.  What is REPL you ask:  Answer here!

An overview of how to set this process can be found here: “Serial REPL“.

Other Info:

  • I used PuTTY for this connection.
  • It looks like the COM port for my CPE changes pretty often, so I have to access the Windows Device Manager every time I want to run this feature.  Mine shows up as “Teensy USB Serial”, and tends to bounce around COM9->11
  • You can’t connect when you’re in bootloader mode:  Get a program running first.
  • Note, on first time connect, you can’t connect in via REPL until the Windows Explorer (auto) opens:  That signifies that the machine is ready.
  • If, when the terminal screen comes up its black/no info, hit ctrl+c to break out of the running program and access the terminal: >>>
  • type help() to see a list of built-in functions.
  • You can use this same connection (before the ctrl+c) to see the output of any module currently running.


Really look forward to seeing what this little board can do!

New Project: Adafruit Trinket NeoPixel LED Longboard

My son and I recently tackled the “Adafruit Trinket NeoPixel LED Longboard” project: Seemed like it would be a good cross between 3d-printing, electronics, and skateboards.  After running through it though, I found a number of problems with the instructions which I submitted here (if you’re going to do this project, be sure to read them).  Unfortunately at the time of this authoring they haven’t updated their project page to address the problems.

In a nutshell, this is what you need to look out for:

  • Need to order two Neopixel LED strips, not one.
  • There are problems with the wiring instructions, based on missing data.
  • Unless you have ninjaflex or nylon, you may want to entirely skip printing/assembling the front ring enclosures:  I printed mine in solid PLA, and they vibrated apart after the first ride (snapping the internal wiring in the process).
  • If you do print the rings, you really do need to use “wire wrap” to do all the wiring:  Larger gauge wire just won’t fit based on the printed models.  The problem I have with this is although you only need a small amount of wire wrap for the project, it’s best if everything is color coded, and buying wire-wrap in multiple colors actually gets a bit expensive.  I ended up using just two colors, and having to label all the wires (which pretty-much makes it impossible to fix if they snap after everything is assembled).

Overall it was a fun project, just seriously hindered by the confusing instructions, based on other issues I list in the above link.

Here’s the end result before the rings fell apart (and I removed them).  Note the metal bracket over the electronics enclosure and front of the  skateboard:  One jumped curb and you’ll have some smashed equipment without it.

First steps with the Adafruit Trinket

I recently picked up a Adafruit Trinket (3.3v), simply because they’re so cheap (about $8).  I like the idea of a tiny small Arduino-ish board.  Since I’m forgetful, below documents the overall process I got to get it working.

End result:  Franken-servo!

End result: Franken-servo!

Resource Links:

First Steps:

For all the documentation on the web, I really wasn’t sure where to start.  There’s all this talk of installing AVRDUDE, etc, but as it turns out it’s really not needed (if using the Arduino IDE). Here’s the streamline approach I finally took:

  • Setup my pre-existing Arduino IDE for use with the Trinket, following these Adafruit docs.
  • Since I’m on a Mac, I didn’t have to worry about installing any drivers, but the “Mac Arduino IDE” app download they provided didn’t work.  Mac said it was “corrupted”.  So instead I had to use the “Slow Way” example they gave.  And other than a few path differences it worked just fine.


  • I was able to successfully run all their examples from the page “Programming with Arduino IDE“.
  • Earlier in the day I had done some servo programming on an Arduino, and I wanted to emulate it on the Trinket.  Thanks to the “Trinket Servo Control” tutorial, and their “Adafruit SoftServo” library, I was able to make it happen.  However, I was unable to create two separate servo objects:  I think I don’t quite grasp the Trinket pinouts.  The above image has two servo’s hooked up to the same pin, so they move the exact same way.

So a successfully first attempt.  Next up, I really need some batteries to make a standalone project with it…

BAT Hat project: Updated

Taken me a while to get back to this project, my “Blind Assistance Technology” (BAT) hat:  Little over a year ago, I blogged about using some Ping Sonar sensors to drive vibrating motors, to turn distance into haptic feedback.  Doing some “trials” at work, the biggest comment was “I don’t like having my head vibrated”.

I thought I’d try a different technique: audio.  Rather than vibrating one’s head, you could simply listen to what the sonar had to tell you.  In theory it seems like a great idea, but as usual in practice, it’s not quite what I expected.  All files are available for download at the bottom.

The Goal:

  • Have multiple Ping sensors around your head, translating the distances into different sounds, in stereo:  Would give you spacial wareness based on the stereo sound.

The Reality:

  • Based on the hardware I choose, it’s not in stereo, nor does it update fast enough.

My current hardware configuration is a Arduino Uno mated with an Adafruit Wave Shield, being fed data from three Ping))) sensors, mounted to some brackets I designed and 3d printed on my Makerbot Replicator (in nylon), being powered by 6xAA batteries attached to the back of the hat.

I thought the wave shield was in stereo when I bought it:  It is not.  Don’t get me wrong, it was easy to solder together and worked immediately, so I have no complaints about that aspect of the hardware.  I simply should have read up on the specs better before settling on it.  Secondly, and unless I’m just missing something (which is possible), each wav file needs to complete before the next beings.  This really limis the ‘audio refresh rate’:  You can only get audio updates as fast as the wav files play back… so unless you’re walking pretty slowly, it’s not quite fast enough.

All that being said, the hardware does work:  But doning the crazy-mad-scientist hat, you can walk around your environment with your eyes closed, and it will give you audio cues when you are within 100cm of something (about the length of an arm):  Is says the letters “F”, “L”, & “R” based on if you’re in range of something.  And to speed up the audio, I detect for multiple directions at once, and made combo audio file sto play back.  Like “F L R”, “F L”, etc.

I generated all the audio via this AT&T site, that does text to speech:    AT&T Natural Voices Text-to-Speech Demo
It saves out all the audio in the exact format the wave shield wants, making that aspect really easy.

The Future:

I think the next step will be swapping out the Arduino\Wave Shield for a Raspberry Pi:  By using PyGame, I can use stereo audio, and play multiple sounds at once.  My hope is to use actual “pinging” sounds rather than speech.  We’ll see what happens…


Connecting the Mac to the Pi

The main hurdle I’ve had with the Raspberry Pi is simply seeing the screen:  Since I don’t have  a spare monitor laying around, it’s plugged in over HDMI to my livingroom TV.  Sitting on my couch,… the text is really small.

Thanks to the awesome people at Adafruit Learning Systems, they’ve provided two tutorials specifically for logging into your Pi remotely over SSH (Secure SHell), and remote-controlling the desktop via VNC (Virtual Network Computing).  This gives you the advantage of not needing a spare monitor, keyboard & mouse to control the Pi:  You can use your current PC’s setup.

I don’t know anything about Linux or sysadmin work, but their tutorials worked exactly as shown and I was connected in no time.  I’m posting this mainly as a reminder to myself how I got all this stuff hooked up…

  • First, you need to get a SSH connection from your computer (in my case, Macbook Air) to the Pi:  Adafruit’s Raspberry Pi Lesson 6: Using SSH shows you how.  Once this is setup, you can easily remotely login from a Terminal on your PC, and take control of the Pi.  But you don’t have access to it’s gui system, only the command-line.
  • Second, to control the Pi’s gui, you need to install a VNC server on the Pi, and a client on your PC (Adafruit recomends RealVNC’s ‘VNC Viewer’).  Their tutorial covers all of this: Adafruit’s Raspberry Pi Lesson 7: Remote Control with VNC.

Once all that software is installed\setup\configured, how do you make the connection?

  • Boot the Pi, wait for it to ‘be ready’.
  • Open a terminal on your PC:  SSH into the pi (put in appropriate ifnet address of the Pi and login name):
    • ssh -l myPiLogin
  • The terminal is now controlling the Pi.
  • Next, start the VNC server on the Pi:
    • vncserver :1
  • Now that you have a SSH connection to the Pi, and the VNC server running on the Pi, you can connect via VNC Viewer on your PC:
  • Open the VNC Viewer app, and connect to the pre-configured server you made earlier:   For example,
  • After entering in the password, the Pi’s desktop should spring to existence on your PC.
If you forget the address of your Pi, you can run ifconfig from the pi itself (which of couse means hooking it back up to a monitor\keyboard) to get it.
Programming Python on the Pi will be so much easier now…

Pi's desktop on my Mac's desktop: Success!