EKF Flags LUA scripting

MarcusL · October 20, 2024, 11:22am

Hi,

Can someone assist me in creating a new Lua binding, for the EKF flags?

I want to create my own neopixel notification led light, for signaling when the copter will accept loiter mode. As i can see, it won’t do that until all EKF flags are ok. Usually the pos_horiz_abs is the slowest at going from red to white.

MarcusL · October 20, 2024, 1:54pm

Alternatively, where can i find the documentation behind “pos_horiz_abs” - i want to know what values it is using to detemine if it is happy or not.

Yuri_Rage · October 20, 2024, 1:55pm

Enable fences, and you’ll get a prearm check for position. No need for scripting.

Do a text search of “prearm” in this source file for most of the reasons for EKF prearm check failures:

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_NavEKF3/AP_NavEKF3_VehicleStatus.cpp

#include "AP_NavEKF3_core.h"

#include "AP_NavEKF3.h"

#include <AP_DAL/AP_DAL.h>

/* Monitor GPS data to see if quality is good enough to initialise the EKF
   Monitor magnetometer innovations to see if the heading is good enough to use GPS
   Return true if all criteria pass for 10 seconds

   We also record the failure reason so that pre_arm_check()
   can give a good report to the user on why arming is failing
*/
void NavEKF3_core::calcGpsGoodToAlign(void)
{
    if (inFlight && !finalInflightYawInit && assume_zero_sideslip() && !use_compass()) {
        // this is a special case where a plane has launched without magnetometer
        // is now in the air and needs to align yaw to the GPS and start navigating as soon as possible
        gpsGoodToAlign = true;
        return;

This file has been truncated. show original

Yuri_Rage · October 20, 2024, 2:27pm

If your GPS is frequently causing prearm failures, you can relax GPS_HDOP_GOOD.

MarcusL · October 21, 2024, 12:26am

Interesting!

So I could enable fences, then use the Lua binding “arming:pre_arm_checks()” to get feedback on whether the system is ready to arm

The EKF calculations going on for determining if the pos_horiz_abs is good or not was more complex than expected

Yuri_Rage · October 21, 2024, 12:32am

If you enable fences (even if none are uploaded), the copter will refuse to arm in any mode until the position flags are valid. You don’t need to script anything, as the LED status will continue to flash yellow for failed prearm checks until all pass. You’ll also get periodic GCS messages stating the same if Yaapu telemetry is present or a GCS is connected.

MarcusL · October 21, 2024, 6:55pm

I understand!

The reason I want to use Lua scripting is to create custom led signals that tell me very specific things during flight.

I tested your solution today, using fences and the prearm lua function, and it worked beautifully.

Thanks!