ardupilot/libraries/AP_Scripting/examples/analog_input_and_GPIO.lua

-- This script is an example of reading a analog pin, PWM in and GPIO

-- for these examples BRD_PWM_COUNT must be 0

-- load the analog pin, there are only 16 of these available
-- some are used by the main AP code, ie battery monitors
-- assign them like this in the init, not in the main loop
local analog_in = analog:channel()
if not analog_in:set_pin(13) then -- typically 13 is the battery input
  gcs:send_text(0, "Invalid analog pin")
end

-- load a input pwm pin
local pwm_in = PWMSource()
local pwm_in_fail = PWMSource()

if not pwm_in:set_pin(50) then -- AUX 1
  gcs:send_text(0, "Failed to setup PWM in on pin 50")
end

-- there are a few combinations of PWM in that will not work
-- this is due to the way interrupts are handled, AUX 1 and 6 cannot both
-- be PWM at once because they use the same interrupt (on Cubes), this should fail
if not pwm_in_fail:set_pin(55) then -- AUX 6
  gcs:send_text(0, "Failed to setup PWM in on pin 55")
end

gpio:pinMode(51,1) -- set AUX 2 to output, gpio:pinMode(51,0) would be input

function update()
  gcs:send_text(0, string.format("voltage: %0.2f, PWM: %i, input: ", analog_in:voltage_average(), pwm_in:get_pwm_us()) .. tostring(gpio:read(51)))

  -- analog_in:voltage_average() the average voltage since the last call
  -- analog_in:voltage_latest() the latest voltage reading
  -- analog_in:voltage_average_ratiometric() the average ratiometric voltage (relative to the board 5v)

  -- pwm_in:get_pwm_us() the latest pwm value in us
  -- pwm_in:get_pwm_avg_us() the average pwm value in us since the last call

  -- gpio:read(pin)
  -- gpio:write(pin, state)
  -- gpio:toggle(pin)

  gpio:toggle(51)

  return update, 1000
end

return update() -- run immediately before starting to reschedule