Lua script to execute "on demand"

Robotic · June 11, 2024, 6:50pm

Hello,

I am trying to set up a Lua script to execute “on demand,” so that I can activate it from a mission, for example, when executing a trigger. Step by step, I have managed to configure the mount to move and take pictures with the script; what I need now is to be able to invoke it when needed from the mission.

I have seen examples where they invoke it from an RC, but that wouldn’t be the case here.

An interesting idea would also be for it to execute upon detecting that the drone stops for a time, say 3 seconds, and then it executes at that moment.

For practical purposes, using a “do set servo” to activate it would be ideal.

I have searched, read, and experimented without success.

Any idea on how to achieve this?

Yuri_Rage · June 11, 2024, 6:52pm

Seems you want to do this while in auto mode. NAV_SCRIPT_TIME is probably the answer:

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/copter-nav-script-time.lua

-- Copter perform a simple maneuver in response to a NAV_SCRIPT_TIME mission command while the vehicle is in Auto mode
--
-- Create a simple mission like below
-- TAKEOFF, Alt:10m
-- NAV_SCRIPT_TIME, command=0 (not used in this script), timeout=30 (seconds), arg1=5 (square width in meters), arg2=10 (square height in meters)
-- RETURN-TO-LAUNCH
--
-- Arm the vehicle (in Loiter mode), switch to Auto and raise the throttle
-- The vehicle should climb to 10m
-- This lua script will be fly the vehicle in square pattern in clockwise direction at the current altitude
-- "arg1" specifies the width (e.g. East-West) in meters
-- "arg2" specifies the height (e.g. North-South) in meters
-- Once the vehicle completes the square or the timeout expires the mission will continue and the vehicle should RTL home

---@diagnostic disable: param-type-mismatch
---@diagnostic disable: need-check-nil

local running = false
local last_id = -1          -- unique id used to detect if a new NAV_SCRIPT_TIME command has started
local start_loc             -- vehicle's location when command starts (South-West corner of square)

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Robotic · June 11, 2024, 8:58pm

Thank you very much for the reference, Yuri.

I will review the code in detail.

Chi_n_Nguy_n · October 22, 2024, 3:10pm

"Hi @Robotic , I want to activate my Lua script only when I flip a switch on my controller. For example, when I’m near the area where I want to use the script, I can just flip the switch to activate it. Is it possible to set it up like that?

Yuri_Rage · October 22, 2024, 3:14pm

The script must execute in a callback loop, polling for the switch position to change. Include logic to execute your custom functions when the switch is in the position you desire.

Chi_n_Nguy_n · October 22, 2024, 3:27pm

That approach could work, but I’m not sure which command to use in a Lua script to check the status of a switch on my controller. I’ve looked through the common Lua scripts for Rover but didn’t find a command for this

Yuri_Rage · October 22, 2024, 3:35pm

It’s the only approach that will work with the current Lua engine.

Here’s one where you’d set RCx_OPTION = 300 and use the cached aux state bindings to switch EKF versions. It’d be better practice to use a global variable to keep track of the switch state and only update values on switch change, but the example gets you the basic idea:

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/AHRS_switch.lua

-- switch between EKF2 and EKF3 on a switch

local AUX_FUNCTION_NUM = 300
local EKF_TYPE = Parameter('AHRS_EKF_TYPE')

function update()
   local sw_pos = rc:get_aux_cached(AUX_FUNCTION_NUM)
   if not sw_pos then
      return update, 100
   end
   if sw_pos == 2 then
      EKF_TYPE:set(3)
   else
      EKF_TYPE:set(2)
   end
   return update, 100
end

gcs:send_text(0, "Loaded AHRS switch for EKF3/EKF2")

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Chi_n_Nguy_n · October 22, 2024, 3:49pm

Got it, I now understand. I was reading your response on Switch off - on Lua script and select 2nd script to control LEDs - ArduPilot Lua Scripting - ArduPilot Discourse, but this explanation was actually much easier to follow. I’ll test it as soon as I can. I’ve also gone through many of your Lua scripts on the forum, and they’ve been a huge help in building my own. Thanks so much for all your help!"