So I have an Arduino Uno lying around and I could not think of any projects except for the ones bundled in the software.

I decided to build a traffic light instead, the catch is that instead of the normal timed change of LED's, I wanted to read the status of our continuous integration server (Jenkins).

Of all tutorials I found on the www, not a single one worked out of the box, so I decided to break it down to it's simplest form and take it from there.

Step 1: Required Items

HardWare.

Arduino (I made use of the UNO V3 but any should work. {Please correct me if I'm wrong.})
Bread Board
Bread Board Jumper Cables
LED's (Red, Yellow, Green)
Resistors (180 Ohm is perfect. {Bands: Brown, Grey, Brown})

Software.

PyCharm (by Jetbrains)
Arduino

Please follow the individual applications install details as set out on their respective websites.

Step 2: Creating the Python Script (PyCharm)

Once PyCharm has been installed on yout computer, copy and paste the following code:

>>> Copy everything below this line <<<

import json
import sys
import urllib2
import time
import serial
# Configurations
ping_server = 30
jenkins_jobs=["Your Job Name Here"] 
ser = serial.Serial('COM3', 9600) 
# Arduino Configuration
SUCCESS = 'b'
FAILURE = 'r'
BUILDING = 'a'
UNSTABLE = 'y'
time.sleep(5)
def get_status(jobName):
    jenkinsUrl = "http://Your Jenkins Server:Port/job/"
    try:
        jenkinsStream   = urllib2.urlopen( jenkinsUrl + jobName + "/lastBuild/api/json" )
    except urllib2.HTTPError, e:
        print "URL Error: " + str(e.code)
        print "      (job name [" + jobName + "] probably wrong)"
        sys.exit(2)
    try:
        buildStatusJson = json.load( jenkinsStream )
    except:
        print "Failed to parse json"
        sys.exit(3)
    return jobName,buildStatusJson["timestamp"], buildStatusJson["result"],
while(1):
    for job in jenkins_jobs:
        status = get_status(job)
#        print status[0], status[2]
        if status[2] == "UNSTABLE":
            ser.write(UNSTABLE)
        elif status[2] == "SUCCESS":
            ser.write(SUCCESS)
        elif status[2] == "FAILURE":
            ser.write(FAILURE)
        elif status[2] == None:
            ser.write(BUILDING)
        time.sleep(ping_server)

Notes:

On Windows 7, the Arduinos COM port number can be seen under the device manager.

Step 3: Creating the Arduino Script (Arduino)

Simply copy and paste the following code into the Arduino Application and upload it to the device.

int incomingByte = 0; // for incoming serial data
void setup() {
  // Green
  pinMode(12, OUTPUT);
  // Yellow
  pinMode(11, OUTPUT);
  // Red
  pinMode(10, OUTPUT);
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
  if (Serial.available() > 0) {
    incomingByte = Serial.read();
  }
  if (incomingByte == 'b') {
    green();
  }
  else if (incomingByte == 'y') {
    yellow();
  }
  else if (incomingByte == 'r') {
    red();
  }
  else if (incomingByte == 'all') {
    all();
  }
}
void green() {
  digitalWrite(12, HIGH);
  digitalWrite(11, LOW);
  digitalWrite(10, LOW);
  delay(1000);
}
void yellow() {
  digitalWrite(12, LOW);
  digitalWrite(11, HIGH);
  digitalWrite(10, LOW);
  delay(1000);
}
void red() {
  digitalWrite(12, LOW);
  digitalWrite(11, LOW);
  digitalWrite(10, HIGH);
  delay(1000);
}
void all() {
  digitalWrite(12, HIGH);
  digitalWrite(11, HIGH);
  digitalWrite(10, HIGH);
  delay(1000);
}