Keep in mind that it's probably cheaper and easier to just buy a cheap or used tablet or phone and have it display a nightscout site.

You need to have basic soldering skills and a basic familiarity with the Arduino environment.

Note: these are the components I used to build mine. You can probably substitute other components, but you're on your own to adapt the code accordingly.

• Adafruit Feather M0 WiFi: the microcontroller that runs the code and drives the displays. Note that I could have used the cheaper Adafruit Feather Huzzah (ESP8266-based) instead, but it was out of stock when I built mine. Using the ESP8266 very likely requires substantial code changes.
• Female Feather headers (16-pin and 12-pin female headers)
• Adafruit LED Matrix Featherwing in the color of your choice
• USB Micro-B cable and USB power supply
• Soldering iron, solder, tape, flush diagonal cutters

If all you want is just the blood glucose display, that's all you need. If you also want a clock (like in the picture shown above), you also need:

• Adafruit Feather Doubler
• A second LED Matrix Featherwing, not necessarily in the same color

Refer to the Adafruit assembly instructions for the various components:

• Feather M0 WiFi
• LED Matrix Featherwing
• Feather Doubler

Assemble the components as follows:

• Solder the additional female headers on the top of the Feather M0 WiFi, do not use the included male headers.
• Solder the included male headers and display modules to the LED Matrix Featherwing(s) per the instructions.
• If using the clock display, solder the included female and stacking headers on the top of the Feather Doubler board.
• If using the clock display, bridge the A0 solder jumper on one of the featherwings.
• Attach all the boards together by placing male headers into female headers as appropriate.

Follow the Adafruit instructions to install the Arduino environment and install the M0 board support for the Arduino IDE. In addition, use the library manager (Sketch→Include Library→Manage Libraries) to install the following libraries:

• Adafruit GFX
• Adafruit LED backpack
• WiFi101
• Time

After installing all the software, try the following examples in the Arduino environment to make sure the hardware is working correctly:

• Blink (File→Examples→01.Basics→Blink): this should slowly blink the red LED on the feather board itself. This makes sure your Arduino environment is properly configured for uploading code to the feather.
• Minimatrix (File→Examples→Adafruit LED Backpack→minimatrix16x8): this should display a few demo patterns on the LED matrix.
  • Change matrix.begin(0x70) to matrix.begin(0x71) to test the second LED matrix, if appropriate.
• Wifi101 (File→Examples→WiFi101-...): use the examples for the Wifi101 library to test the internet connectivity. Make sure to adjust SSID and password according to your network and insert WiFi.setpins(8,7,4,2) in the setup() function to use the pins specific to the Feather M0 board.

Open the code for this project and save it into your Arduino sketch folder. Then adjust the parameters at the top of the file as follows:

• WiFi network SSID and passphrase
• Nightscout server address
• Timezone
• Display brightness

Upload the sketch and after a bit you should see the time and blood glucose value from your Nightscout server!

If you build one of these, I'd be very interested to hear about your experience. Please let me know via email: ruud at ruud dot org.