device = hid_open(0x1209, 1)

if device == nil then
   print("No device!")
else
   dataref("low_vac", "sim/cockpit2/annunciators/low_vacuum", "readable")
   local prev_low_vac
   function low_vac_indicator()
      if low_vac ~= prev_low_vac then
	 if low_vac > 0 then
	    hid_write(device, 2, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
	 else
	    hid_write(device, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
	 end
	 prev_low_vac = low_vac
      end
   end

   do_every_frame("low_vac_indicator()")
end