BuildStatusTrafficLight

Project BuildStatusTrafficLight
A traffic light showing CI build status
Status	Completed
Contact	bertrik
Last Update	2018-11-23

Introduction

The end result of this project is a traffic light that shows the status of a software build.

It can show the following statuses:

• red: build has failed to compile
• yellow: code compiles but a unit test fails
• green: code compiles and all unit tests are successful
• yellow flashing: build status unknown, e.g. still starting up, connection problem, or we receive a status we don't understand

Status

It works!

 2018-11-22 Added python script to poll the Jenkins build server and control the traffic light over its serial connection
 2018-11-20 Added command interpreter for control over serial port, removed audio
 2018-11-18 Soldered new, brighter LEDs into it and connected the ESP8266, no sound yet
 2018-11-02 Played with ESP8266 software, particular playing audio using the 1-transistor-circuit
 2018-10-30 Received that hardware, opened it up etc.

Future, things I would do better next time:

• configure LEDs for common anode, so the ESP8266 sinks current instead of sourcing it
• rethink audio, the audio using ESP8266Audio library uses pin Rx, making serial comms impossible, perhaps just use PWM?
• perhaps just remove the WiFi network again, WifiManager blocks startup until a WiFi connection is established. We don't need WiFi if we connect over serial port.

Hardware

I use an ESP8266 (Wemos D1 mini) along with a modified toy traffic light.

The toy traffic light lights the lanterns in order, speaking some Chinese for each lantern. The lanterns are basically white LEDs behind a colored piece of transparent plastic.

I replaced the white LEDs with high-brightness coloured ones (red, orange, green). I removed the original circuit (8-pin chip) and put in an ESP8266 to accept commands and control the LEDs. It can source about 12 mA and sink about 20 mA of current, I'm using a single 150 ohm resistor in the common ground wire of the LEDs (couldn't find a 100 ohm resistor at the space ...)

The toy traffic light features a built-in speaker. I haven't put in a sound circuit yet. Usage of the ESP8266Audio library in software is problematic because this library sends audio over pin Rx, making serial communication difficult.

Software

Source code can be found on github.

It is written in C/C++ for Arduino for quick and easy development.

The traffic light listens on the serial port to receive commands (like 'set 1'), A python script running on a PC inside the LAN script polls the Jenkins server over ethernet.

Getting build status

To get the Jenkins build state, poll the following URL to receive JSON status data

 http://jenkins/job/jobname/lastBuild/api/json

where jobname is the name of your build job. Then look for the value of the "result" field at the top level of the JSON, it can take on the following values:

• "FAILURE"
• "UNSTABLE"
• "SUCCESS"
• null, in case a build is still in progress

External links

• Jenkins traffic light plugin seems to have the wrong kind of interface, designed to directly drive a bunch of wireless 230V sockets instead of just sending the information like I need
• Signalling Your Jenkins Build Status with a Mini USB Traffic Light