#018 FretBoard

FretBoard is a multi-project build status indicator, using a WS2811-based LED Strip to display the status of each project.

Full details of the project are available at fretboard.tardate.com

Done:

parse build status from the net using Ethernet shield
driving the LED Array with basic build status indication
added LED effects (glow) using timer driver
added visual indicator when the build status is refreshed and builds-in-progress
the physical build - housing this in a suitable case for display
wrap up the doco

Notes

The Build Status Web Response

We get build status from a web server that supports a simple HTTP 1.0 CSV response. This is probably a proxy to the actual build server. See the fretboard web repository for an example of a proxy that can handle Circle CI JSON API and CruiseControl XmlStatusReport response formats.

The response looks like this:

$ curl -i -0 --raw http://fretboard.tardate.com/status.csv

HTTP/1.1 200 OK
Connection: close
Content-Type: text/csv;charset=utf-8
Content-Length: 288
X-Content-Type-Options: nosniff
Server: WEBrick/1.3.1 (Ruby/2.0.0/2014-11-13)
Date: Sun, 01 Feb 2015 09:04:18 GMT
Via: 1.1 vegur

dummy_project_1,Sleeping,Success
dummy_project_2,Sleeping,Failure
dummy_project_3,CheckingModifications,Success
dummy_project_4,CheckingModifications,Failure
dummy_project_5,Building,Success
dummy_project_6,Building,Failure
dummy_project_7,Unknown,Success
dummy_project_8,Unknown,Failure

Each line of the CSV response includes three elements:

project name
build activity (CheckingModifications,Building,Sleeping,Unknown)
build status (Success,Unknown,Failure)

A couple of features make this easy to deal with:

HTTP 1.0 means the Arduino doesn’t need to deal with chunked-encoding.
The CSV format is easy to parse either natively from EthernetClient or with the assistance of a library like TextFinder
project build status are provided in alphabetical order, hence the Arduino doesn’t need to worry about ordering of results

Parsing the Web Request

I’m using TextFinder to parse the web response. Note that the GitHub repository version of TextFinder is an enhanced version of the original library available from the Arduino Playground.

Other libraries that could be used are amcewen/HttpClient and interactive-matter/HTTPClient.

Power

The LED strip requires 5V and with all 24 LEDs on, current should max out at 1.44A (0.3W * 24 / 5V).

For testing, I’m powering the LED Array from a 5V 2A adapter and the Arduino from USB.

For the final build, I’ll be powering the Arduino from the same 5V adapter powering the LEDs (direct to the 5V pin on the Arduino). There is lots of advice on how to do this e.g. here

along with strong caveats since the 5V pin bypasses the onboard regulator, and it is essential to ensure no other power source is simulatneously provided to the Arduino. However, the 5V adapter I am using is regulated, and under test it has worked fine to power the Arduino and LED array together.