gpio.rb

class GPIO
  attr_reader :id
  @@DIR = "/sys/class/gpio"
  @@ATTRS = [:value,:direction,:edge,:active_low]
  class << self
    [:export,:unexport].each{|e| define_method(e){|id| !!File.write("#{@@DIR}/#{e}",id)}}
  end
  def initialize(id)
    @id = id
    @@ATTRS.each{|a| instance_variable_set("@#{a}_path","#{@@DIR}/gpio#{id}/#{a}")}
  end
  def to_io; @io||=File.new(@value_path); end
  def chmod(mode); File.chmod(mode,*@@ATTRS.map{|a|instance_variable_get("@#{a}_path")}); self; end
  def chown(owner,group); File.chown(owner,group,*@@ATTRS.map{|a|instance_variable_get("@#{a}_path")}); self; end
  def exported?; File.exists?(@value_path); end
  def export; self.class.export id; self; end
  def unexport; self.class.unexport id; self; end
  def input?; File.read(@direction_path).chomp == 'in'; end
  def output?; File.read(@direction_path).chomp == 'out'; end
  def set_input; File.write(@direction_path, 'in'); self; end
  def set_output_low(v=true); File.write(@direction_path, v ? 'low':'high'); self; end
  def set_output_high(v=true); set_output_low(!v); self; end
  def low?; to_io.rewind; to_io.read.chomp == '0'; end
  def high?; !low?; end
  def set_low(v=true); File.write(@value_path, v ? '0':'1'); self; end
  def set_high(v=true); set_low(!v); self; end
  [:none, :rising, :falling, :both].each do |edge|
    define_method("set_edge_#{edge}"){ File.write(@edge_path, edge); self }
    define_method("edge_#{edge}?"){ File.read(@edge_path).chomp.to_sym == edge }
  end
  def active_low?; File.read(@active_low_path).chomp == '1'; end
  def set_active_low(v = true); File.write(@active_low_path, v ? '1':'0'); self; end
  class << self
    def select(gpios, timeout:nil)
      _,_,r = IO.select(nil,nil,gpios,timeout); r
    end
  end
  def select(timeout:nil)
    self.class.select([self],timeout:timeout) ? self : nil
  end
end