Cardinal Compass Wearable

Community Project: Cardinal
Anyone who would like to contribute feel free to add your thoughts here. If you need to make purchases to support your contribution to the project, see this thread , and direct message @amal or @Satur9 with details. Project threads can get a little out of hand with tons of people brainstorming. I ask that you limit your messages to the topic at hand. Try to condense multiple messages into one post.

First off, this project has been created by 24HourEngineer (McSTUFF). They are loosely affiliated with Grindhouse Wetware, and they originally approached me for help with this project a year ago. They have posted all the content in the public domain, so I’m not hesitant sharing. Credit where credit is due though. McSTUFF, if you’re around you can feel free to weigh in with insights and direct our efforts.

The idea with this project is to create a small wearable device (25mm x 5mm disc) that will vibrate when the user is facing north. Wearing the device as a pendant or on a belt will ensure it remains facing forward. This idea is similar to a very old project called the Northpaw, and also Lepht Anonym’s attempts at creating an implantable version called the Southpaw.


Lepht and McSTUFF would like to transition the build to an implantable version (and they can achieve it with Grindhouse Wetware and Cassox’s PMMA encapsulation experience). The only way I see that working is with rechargeable batteries, though. Even LIR2032 batteries will offgas and may compromise any encapsulation, so I’m not comfortable making that into a “product”. Any effort we put into making a tiny wearable device will be in the public domain, though. So if some enterprising biohackers want to create an implantable version themselves, more power to them.

McSTUFF has already shared a GitHub repo with the code and a section of their blog detailing the build journey.

I made an earlier prototype before linking up with McSTUFF, which was made from a BBC micro:bit v1 with a lithium-ion battery. It was compact and easy to set up, with a compass module on-board. Unfortunately the accuracy was pretty terrible and all the users abandoned it.

The current iteration of the Cardinal uses a BNO055 IMU to achieve much more accuracy. It was being paired with a 32u4 MCU. The MCU would trigger some BJT transistors that would drive some vibrating disc motors. McSTUFF also had some ambitions to incorporate bluetooth, although I don’t know the details of that.

Next Steps:

  • Prototype with some development boards until we have reliable enough performance
  • Test low power motor drive (capacitor bank with LIR2032?)
  • Begin designing custom PCB

Current collaborators: @Satur9


I really like the idea of this project and I want this in a belt buckle! I’ve acquired an ATMega32u4 in the form of a Teensy 2.0 and a BNO055 breakout board from Adafruit. I worked up bare-bones bit of firmware that initialized the BNO055 in compass mode and reads the X value from the euler registers. It outputs that on a NeoPixel ring so that, in theory, the light will point North.

I haven’t done anything with calibration yet, but it doesn’t seem to bad. Here’s the repo for the code: Bitbucket

Next steps are:

  • Add calibration
  • Figure out how to make it work standing up as well as laying down
  • Switch from the NeoPixel to the little vibration motor I have.
  • Design a custom PCB and belt buckle housing

If you want/need help with that feel free to reach out

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I absolutely will. I’ve never designed a PCB before and it’s pretty intimidating.

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