Adafruit Feather M0 Express

The courier showed up today, with a really neat new board from Adafruit – the Feather M0 Express. It is essentially a break out board for the Microchip (formerly Atmel) ATSAMD21G18, which is the same 32-bit 48MHz ARM M0+ micro used in the Arduino Zero, plus a 2MB flash memory, RGB LED, and a LiPoly charger. It’s not too expensive at $20USD, nice and tiny, and I think could be a real hit.

Using the Feather M0 Express from Arduino IDE almost couldn’t be easier – just add the Adafruit Board Manager URL to your Arduino IDE settings, then install the “Adafruit SAMD Boards” – instructions at .

However, the really exciting new option available with this new board, is CircuitPython – Adafruit’s implementation of MicroPython. Getting setup for CircuitPython is super easy, though the documentation is still under development so it might seem a bit intimidating at first read. Here’s what I did:

  1. Download the latest CircuitPython uf2 file for your board from
  2. Connect the Feather to your computer via USB
  3. Put the Feather in to bootloader mode by “double clicking” the reset button. You’ll know it works when the #13 LED starts fading on and off.
  4. Copy the uf2 file from step 2, on to the FEATHERBOOT USB drive that should have appeared in step 3.  Wait a few seconds.

There should now be a USB drive available called CIRCUITPY, and a virtual serial port available.

Using your favourite serial console with the virtual serial port gives an interactive terminal, aka REPL, which can be used directly as below. Or, just save a source file as in the CIRCUITPY drive to get your program to run at boot.

Adafruit CircuitPython 0.9.5 on 2017-04-14; Adafruit Feather M0 Express with samd21g18
>>> print("hi")
>>> help()
Welcome to Adafruit CircuitPython 0.9.5!

Please visit for project guides.

Built in modules:
(list continues)

Let’s make the “hello world” of embedded programming (but this time, done on-target using tab completion!):

>>> import digitalio
>>> import board
>>> import time
>>> with digitalio.DigitalInOut(board.D13) as led:
...     led.switch_to_output()
...     while True:
...         led.value = 1
...         time.sleep(0.5)
...         led.value = 0
...         time.sleep(0.5)


We’ve been doing a bit of work on the maker space lately, and this website too!

For the last several years, our website has been hosted on a VPS provided by Blair (thanks so much!) Now that we’ve got a reliable Internet connection at the makerspace though, we’re able to host the site from an on-site computer that’s already hosting the Valley Workspace, Dunedin Electric Bikes, and Quarantine Island sites, and some makerspace affiliated projects like Dunedin food truck tracker If you’re interested in how the Internet works, want to host a site, or have fun ideas for things to connect to the machine, just say the word!

As part of the website move, I’ve upgraded the WordPress install, and am planning to embark on a clean out of the Users (we’ve apparently got ~45k) and Comments databases. I’ll try to keep from deleting legitimate accounts, but if your dspace account disappears, just let me know and I can restore it.

Finally, some donated lights were installed last weekend, in the room adjoining the bike workshop, to light up that web server!


Using the inductor tester

inductor tester
The inductor tester, and inductors used for examples below

A few weeks back, we had a talk on KiCad (presentation available at ) where we ordered some PCBs to make an inductor tester (Henryometer?) from dirty PCBs. Those boards came in this week, and a few folks have already put theirs together. This post aims to be a quick guide to the usage of the tester; if you’d like to build one yourself just let Ian know, parts cost is $15. You’ll need an oscilloscope and a current-limited DC power supply to make use of it.

Continue reading “Using the inductor tester”

Debugging AVRs (without Atmel Studio)

This post is somewhere between a guide and a collection of notes, aimed at debugging programs for AVR microcontrollers (like the ones in most Arduinos) “on target”. We’ll be using an AVR Dragon connected to the target micro via the normal 6-pin programming header, with a Mac or Linux PC as the host.

Although this is a bit more advanced than most of our other projects, it’s really quite approachable and is a very powerful technique for fixing AVR software problems.

From a high level; we’ll use a debugging program on a Mac (or Linux, Windows, etc) “host” computer, which communicates with a Dragon “In Circuit Emulator” (ICE) via USB to debug a buggy program running on the “target” AVR, which is presumably running in some circuit we’re interested in. Small variations might apply for Windows hosts, using JTAG instead of DebugWIRE, other debugger tools (Atmel JTAGICE mkII for example), etc.

Continue reading “Debugging AVRs (without Atmel Studio)”

ShapeOko Toolchain and Impressions

G’day everyone.  Thank you for your kind attention during Thursday’s (9 August 2012) presention on my initial playtime with Paul’s Shapeoko CNC router.  Paul encourages people to use the router (with care) to MAKE!

As requested, I have posted the presentation slides here.  Too late to include in the presentation, but cool tools for CNC folks to use include the OpenScam toolpath visualistion tool at and the ubercool half-tone application that MetalFusion made to convert grayscale images into .dxf and Gcode files so that you can engrave photos into materials with a cone-shaped bit.  The utility can be downloaded free from here, and examples of the output can be seen here

ShapeOko Presentation Slides