Edge computing prototyping with Coral

Edge computing when used with Sigfox opens a complete new set of possibilities & applications:

  • Apply Machine Learning (ML) to detect vehicles or bystanders in a video streams and send the results periodically
  • Use any tensorflow model, upload it to your board and get the results in your Sigfox backend

In this article, you'll learn how to:

  • Download schematics to build your MRQ board
  • properly setup & configure your MRQ board to send information from your Coral board to Sigfox Cloud

What is the Coral board?

Coral is a Google company that produces dedicated chipsets and software that enables edge machine learning capabilities. Their ASIC can be added to an IOT device so that it becomes possible to run inferences locally, off-line, at low cost and high power efficiency. Coral has a set of products ranging for development kits, add-on cards, SOM or module.

To facilitate the development of solutions based on Coral ML and on Sigfox, we have developped a daughter card, called MRQ board, that fits on top of Coral dev kits.

The "Coral dev board" and the "Coral dev board mini" use a 40 pin GPIO connector with the same form factor as the Raspberry Pi, but for the moment it is not compatible with the Raspberry Pi as it uses UART3 (which is not available on Raspberry Pi).

 MRQ Board prototype:

MRQ Board 3D view:

Getting started with Coral and Sigfox

If you want to get started with using the Coral board, check out Markku Lepisto's video series:

In the mean time, get a MRQ board produced by your favorite PCB manufacturer. All the schematics are down below.

On the MRQ board, you can choose to use either the Liteon module or the Seongji (ex WISOL) module.

- Before you choose the module, first you need to check which Radio configuration you want to use the board in. For that, please check Build's article on RC.

- At the time of the writing of this article, Seongji has different part numbers supporting RC 1, 2, 3c, 4, 5, 6 and 7.

- At the time of the writing of this article, Liteon has one part number supporting all RC 1, 2, 3c, 4, 5, 6 and 7.

Using the MRQ board with Coral - command line

The board uses simply the pins 7 and 11 for the UART3 and all other connections are pass through. This means that you can use it with Coral's environmental sensor board.

1.  Get your Coral board up and running, as per Markku's video.

2.  Make sure that your board has been registered on a proper Sigfox contract. You can buy a contract online from Sigfox Buy. Please note that you cannot use the "Activate my dev kit" option at this point in time.

3.  Log on the Coral board from your laptop.

 MBP$ mdt shell 

4.   Install Minicom (needed once)

 mendel$ sudo apt-get install minicom 

5.   Run Minicom on serial interface for UART3 : /dev/ttymxc2

  • If it is a Seongji module 9600 bauds, 8 bits data, Parity non, 1bit stop:
mendel$ sudo minicom -b 9600 -o -D /dev/ttymxc2 
  • If it is a Liteon module (115200bps, 8 bits data, Parity non, 1bit stop):
 mendel$ sudo minicom -b 115200 -o -D /dev/ttymxc2 

6.  From Minicom you can send out the AT commands to the module

ID == 0x00045678
PAC == 5445535420504143

7. You should now be able to see your message with payload "BABE" in Sigfox backend.

Manufacturing the MRQ board

In the project file underneath you will be able to find:

  • The schematics 
  • The layout files (Altium and Gerber)
  • The bill of material (for both Liteon and Seongji options).

Licence and support

 Sigfox make available on-line this design example for the whole ecosystem in order to be reused, customized and industrialized in Sigfox end-products. It is provided for free with its associated documentation. Sigfox do not guaranty technical support for users of this reference design. Possible updates of the package could follow in order to add test and characterization data or design optimizations.