Firefly Design LLC

Firefly Ice: An Open Source Wearable / Internet of Things Platform

Firefly Ice: Timing Demo

Posted by Denis Bohm on October 06, 2014. 0 Comments

The Firefly Ice has a quick simple proof of concept "timing" demo.  This works by using two Firefly Ice devices.  Each device recognizes an event.  When the event is recognized the accelerometer data is saved from right before and right after the event.  The saved data is synced from both devices to the Firefly Utility app and the timing between the two events is shown in a graph.

Checkout the Timing Demo page for details.


Firefly Ice: Raw Data Capture

Posted by Denis Bohm on October 06, 2014. 0 Comments

 When working on algorithms it is very convenient to be able to easily capture raw sensor data from the Firefly Ice to use for offline development.  The Firefly Utility iOS app has a page that allows raw data to be recorded and synced to your iCloud account.  From iCloud it is easy to access that data from your Mac.

Checkout the Raw Data Capture page for details.


SXSW 2014 Workshop: The Complete Hardware Crash Course

Posted by denisbohm on February 06, 2014. 0 Comments

I'm looking forward to holding a workshop at SXSW 2014: The Complete Hardware Crash Course. It will be on March 11th at the AT&T Executive Education and Conference Center.

The workshop will cover the complete process of creating a small low power connected device by leveraging open source hardware and software. This includes electronics, mechanical parts, firmware, software, FCC testing, production, and more.

You must signup in advance to attend SXSW workshops.  To reserve a seat, please go here:

Hope to see you at SXSW!


Firefly Ice Blue: Test Fixture

Posted by Denis Bohm on February 05, 2014. 0 Comments

The test fixture is used during production testing and programming.  It has spring loaded pins that make contact with the test points on the PCBA.  A plastic adapter holds the spring loaded pins in place and guides the PCBA into place.  This design makes it easy to momentarily hold the PCBA in the test fixture while the testing and programming take place.  The test points are brought out to a standard JTAG SWD connector, USB connector, and battery connector.  There is also a reset button.

The following image shows the test fixture with and without the PCBA in place:

Firefly Ice Blue: Production PCB Assemblies

Posted by denisbohm on December 09, 2013. 0 Comments

The first production batch of 1,500 PCBAs have been completed and tested. It's pretty exciting to see a few boxes of components turn into completed assemblies!


3,000 Components

3,000 Components


Complete PCBAs

1,500 Complete PCBAs

Firefly Ice Blue: FCC Testing Completed

Posted by denisbohm on December 09, 2013. 0 Comments

Firefly Ice Blue has passed FCC testing!

Here is the Firefly Ice on the clear plastic table in the RF anechoic test chamber (tiny black device in the lower right):



RF Anechoic Chamber

RF Anechoic Chamber


If you are thinking of making a product with a radio there are a couple of things to keep in mind when designing your device to make things easier when the time comes for FCC testing.

1)  Make it easy to bypass the antenna and matching circuit to bring out the RF signal via a 50 Ohm SMA connector.  This allows the device to be directly connected to a network analyzer as required for a number of tests.



2) Prepare test software to place the Bluetooth 4.0 radio into Direct Test Mode (see the Bluetooth Specification) with various parameters.  You will be asked to put your device into a direct test mode and transmitting on various frequencies, so make that easy and quick in your app.

iOS App w/ Radio Direct Test Mode

3) Bring a couple of chargers and computers to use with your device for measuring conducted emissions.  Since your device is so low power, you will actually be mainly testing the chargers and laptops conducted emissions rather than your devices.

Conducted Emissions Testing

Firefly Ice Blue: Core Plastics

Posted by denisbohm on December 09, 2013. 0 Comments

Firefly Ice Blue core molds are ready!

The molds have been through a couple of rounds of tweaks and sample runs.  These are the latest plastics samples:

These are the plastic parts after assembly:

Firefly Ice Blue: Core Enclosure

Posted by denisbohm on October 08, 2013. 0 Comments

Firefly Ice Blue Core Parts

The Firefly Ice Blue core enclosure design files are now available:

GitHub: Firefly Ice Mechanical

The Firefly Ice Blue core enclosure design has 4 elements:

  • plastic “back” in black PC
  • plastic “shell” in colored PC
  • plastic “spacer” in black PC
  • plastic “top” in clear PC

The spacer and top are co-molded into a single piece, so there are only 3 parts for final assembly.  The final assembly process is very simple:

  1. Press the top/spacer into the shell.
  2. Bond the top/spacer to the shell with a solvent applied to the inner seam.
  3. Place the electronic assembly onto the mounting posts.
  4. Snap the back piece on.

The shell will come in green, pink, blue, and black :


The core parts are all generated by a Python script run inside Rhino 3D.  That makes it easy to tweak the design.

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