source: de.wigbels.ruby/hothotread/hothotpiper_power.rb @ b62bf13

require 'pi_piper'
include PiPiper

mypath = File.expand_path(File.dirname(__FILE__))
trigger_step = 1.0 / 96
counter = 0

def last_rrd_count(concretepath)
  val = 0.0
  handle = IO.popen("rrdtool lastupdate #{concretepath}")
  handle.each_line do |line|
    m = line.match("^[0-9]*: ([0-9.]*) [0-9.]*")
    if m
      val = m[1].to_f
      break
    end
  end
  return val
end


watch :pin => 11, :trigger => :falling  do
  puts('updated power consumption')
  counter = counter + trigger_step
  trigger_update = trigger_step * 3600000.0
  system("rrdtool update #{rrdpath} N:#{counter}:#{trigger_update}")
end

rrdpath = mypath + "/power.rrd"
counter = last_rrd_count(rrdpath)
PiPiper.wait