Controlling LED on beagleboard-xm on Ubuntu Linux from Ruby.

gistfile1.rb

# control led on beagleboard.
class BeagleBoardXmLed

  LED_FILE_FORMAT =
    "/sys/devices/platform/leds-gpio/leds/beagleboard::@name@/brightness"

  # led: ledname (usr0 : usr1 : pmu_stat)
  def on(led)
    control(led, 1)
  end

  # led: ledname (usr0 : usr1 : pmu_stat)
  def off(led)
    control(led, 0)
  end

  # led: ledname (usr0 : usr1 : pmu_stat)
  def status(led)
    File.open(filepath(led)) do |f|
      state = f.read.chomp
      return (state == "1")
    end
  end

  # led: ledname (usr0 : usr1 : pmu_stat)
  # interval: brink interval
  # count: blink count
  def blink(led, opts = {:interval => 1, :count => 5})
    interval = opts[:interval]
    count = opts[:count].to_i * 2

    count.times do
      status(led) ? off(led) : on(led)
      sleep interval
    end
  end

  private

  # led: ledname (usr0 : usr1 : pmu_stat)
  # output: 1 or 0
  def control(led, output)
    check_output output

    File.open(filepath(led), "w") do |f|
      f.print output.to_s
    end
  end

  # output: 1 or 0
  def check_output(output)
    unless [1,0].include? output
      raise ArgumentError.new "invalid control output:#{output}"
    end
  end

  # led: ledname (usr0 : usr1 : pmu_stat)
  def filepath(led)
    filepath = LED_FILE_FORMAT.sub(/@name@/, led.to_s)
    raise "no such device:#{led}" unless File.exist?(filepath)
    filepath
  end
end

if __FILE__ == $0
  led = BeagleBoardXmLed.new
  led.blink :usr0, interval:0.1, count:10
  led.blink :usr1, interval:0.1, count:10
  led.blink :pmu_stat, interval:0.1, count:10
end