WiringPi PWM Test

Gemfile

source 'https://rubygems.org'
gem 'wiringpi'

led_pwm.rb

require 'rubygems'
require 'bundler/setup'
require 'wiringpi'

$io = WiringPi::GPIO.new
PIN = 6 # GPIO pin 25
$io.mode PIN, OUTPUT
FRAME = 1.0/50.0
$pulse_width = 0.0
$pulse_off = FRAME

def set_duty_cycle(duty_cycle)
  if (duty_cycle == 0)
    $pulse_width = 0
    $pulse_off = FRAME
  else
    $pulse_width = FRAME * (duty_cycle/100.0)
    $pulse_off = FRAME - $pulse_width
  end
end

def pwm
  puts "Light is online."
  while true
    $io.write PIN, HIGH
    sleep $pulse_width
    $io.write PIN, LOW
    sleep $pulse_off
  end
end

t = Thread.new { pwm }

100.downto(1).each do |duty_cycle|
  set_duty_cycle duty_cycle
  puts "Set #{duty_cycle}%."
  sleep 0.1
end

1.upto(100).each do |duty_cycle|
  set_duty_cycle duty_cycle
  puts "Set #{duty_cycle}%."
  sleep 0.1
end

Basically works, must be run as root.
https://www.dropbox.com/s/12ojde9n9suugbl/pwm-led.jpg