Multi-process PID control

kettle_control.rb

 #!/usr/bin/env ruby

 require 'brewby'

 Signal.trap("INT") { exit }
 heat_reader, heat_writer = IO.pipe
 heat_pid = fork do
   heat_writer.close
   adapter = Brewby::Outputs::Test.new
   output = Brewby::HeatingElement.new adapter, pulse_range: 5000

   loop do
     duty_cycle = heat_reader.gets.to_i
     output.pulse_width = duty_cycle
     output.pulse
   end
 end
 heat_reader.close

 temp_reader, temp_writer = IO.pipe
 temp_pid = fork do
   temp_reader.close
   input = Brewby::Inputs::Test.new

   loop do
     reading = input.read
     temp_writer.puts reading
   end
 end
 temp_writer.close

 pid = Temper::PID.new maximum: 5000
 pid.tune 44, 165, 4
 pid.setpoint = ARGV[0].chomp.to_f

 puts "Beginning temperature control.  Setpoint: #{pid.setpoint}"

 loop do
   reading = temp_reader.gets.chomp.to_f
   if reading
     width = pid.control(reading).to_i
     heat_writer.puts width
     power_level = ((width / 5000.0) * 100).round(2)
     puts "Target: #{pid.setpoint}\tActual: #{reading}\tPulse: #{width}\tPower: #{power_level}"
   else
     puts "Faulty or no reading from Sensor"
   end
   # slowing it down for demonstration purposes
   sleep 1
 end

output

Pandora brewby-web (master) bin/kettle_control 154.0
Beginning temperature control.  Setpoint: 154.0
Target: 154.0	Actual: 91.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 138.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 122.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 77.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 146.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 84.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 91.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 143.0	Pulse: 5000	Power: 100.0
Target: 154.0	Actual: 97.0	Pulse: 5000	Power: 100.0