(WIP, can be tested) Artificial horizon (AHI) tilt correction when using camera tilt with servo or gimbal

[mattiras]

I have been working with code that keeps the AHI line on horizon even if camera is tilted with servo or gimbal. It also takes to account if CAMSTAB is activated. Also I made new OSD element that shows camera tilt angle.

It is working already but now I am looking a way to hide the AHI if the Camera Pan is used and panned some defined amount. Since the AHI will no longer be reliable because of the pan+tilt movement.

I have been looking how to do that all day but can't pin point where in the code I could disable the AHI. Could somebody, who knows AHI related code, point me to right direction?

Below is the main code how I did the correction, but surely there is more, tilt servo settings etc. I will make a branch after I get that last function working. Never committed so have to learn that too. You can also push me towards easiest way to commit!

    case OSD_ARTIFICIAL_HORIZON:
        {
            float rollAngle = DECIDEGREES_TO_RADIANS(attitude.values.roll);
            float pitchAngle = DECIDEGREES_TO_RADIANS(attitude.values.pitch);          
//new code start
            if (osdConfig()->tilt_servo_pwm2centideg != 0){
                float tiltOffset = DEGREES_TO_RADIANS(osdGetTiltServoOffset()) ;

                if (IS_RC_MODE_ACTIVE(BOXCAMSTAB)) {
                    tiltOffset -= pitchAngle;
                    pitchAngle = 0;
                }
                pitchAngle -= tiltOffset;
            }
//new code end            
            pitchAngle -= osdConfig()->ahi_camera_uptilt_comp ? DEGREES_TO_RADIANS(osdConfig()->camera_uptilt) : 0;
            pitchAngle += DEGREES_TO_RADIANS(getFixedWingLevelTrim());
            if (osdConfig()->ahi_reverse_roll) {
                rollAngle = -rollAngle;
            }
            osdDrawArtificialHorizon(osdDisplayPort, osdGetDisplayPortCanvas(),
                 OSD_DRAW_POINT_GRID(elemPosX, elemPosY), rollAngle, pitchAngle);
            osdDrawSingleElement(OSD_HORIZON_SIDEBARS);
            osdDrawSingleElement(OSD_CROSSHAIRS);

            return true;
        }

[MrD-RC]

Why not just submit a PR?

[daijoubu]

I think he's looking for suggestions with how to erase the AHI as you can't just skip the draw calls.

[MrD-RC]

The current AHI sets the last coordinates to blank before drawing the new AHI symbols. But I think this could potentially be improved so that only changed cells are updated.

[mattiras]

I ended up simply feeding the AHI with values 90 for pitch & 0 for roll so the AHI goes out of sight.

I have been able to confirm the functions with normal servo setup but cant confirm it with a gimbal.

Anyone care to test it? Please try the CAM STAB mode too.
New settings:

      - name: osd_pan_servo_hide_ahi
        description: Hide AHI if pan servo panned defined +/- amount of degrees. 0 for disable.
        field: pan_servo_hide_ahi
        min: 0
        max: 180
        default_value: 20
      - name: osd_tilt_servo_index
        description: Index of the tilt servo, used to adjust osd AHI direction based on camera tilt. Note that this feature does not work with continiously rotating servos.
        field: tilt_servo_index
        min: 0
        max: 16
        default_value: 0
      - name: osd_tilt_servo_pwm2centideg
        description: Centidegrees of tilt servo rotation us PWM signal. A servo with 180 degrees of rotation from 1000 to 2000 us PWM typically needs `18` for this setting. Change sign to inverse direction.
        field: tilt_servo_pwm2centideg
        min: -36
        max: 36
        default_value: 0
      - name: osd_tilt_servo_indicator_show_degrees
        description: Show the degrees of offset from centre on the tilt servo OSD display element.
        field: tilt_servo_indicator_show_degrees
        type: bool
        default_value: OFF

Tilt servo element:
| 165 | OSD_TILT_SERVO | x.0.0 | |

Branch:
https://github.com/mattiras/inav/tree/Camera-Tilt-AHI-compensation