--update data from redstone channels (sensors)
function UpdateSensors()
  RedstoneBottom = rs.getInput("bottom")
  RedstoneTop = rs.getInput("right")

  --
  if RedstoneBottom then
    rs.setOutput("left", true)
  elseif RedstoneTop then
    rs.setOutput("left", false)
  else
    --
  end
end

UpdateSensors()

repeat
  event,p1,p2,p3 = os.pullEvent()
  if event=="redstone" then
    UpdateSensors()
  end
until event=="char" and p1==("q")