ModalAI Forum

Our upcoming SDK 1.8.0 will have a release 1.18 based version of PX4. The package we are testing with can be found here: http://voxl-packages.modalai.com/dists/qrb5165/dev/binary-arm64/voxl-px4_1.18.0-1.0.9-202610051650_arm64.deb. PX4 parameters are different in this release than the 1.14 based versions so that needs to be considered. Our voxl-px4-params utility has been updated for this already and will be part of SDK 1.8.0. Directly building the tip of mainline should also work although that hasn't been tested for a few months.

HI @oiler251 , we will work on a more detailed step by step guide for debugging VIO. Meanwhile, you may found the below unofficial guide useful. VOXL 2 / OpenVINS Drift Troubleshooting Guide Applies to: Starling 2 / Starling 2 Max and other VOXL 2 vehicles running voxl-open-vins-server with PX4 How to use this guide The steps are ordered by cost × likelihood: the first few take minutes and catch the problems that cause most "my drone drifts" reports. Each step has a pass/fail check. Don't skip ahead. If a step fails, fix it and restart from Step 1, because a fix upstream often changes what you see downstream. The pipeline you're debugging, end to end: tracking cams + imu_apps ──► voxl-open-vins-server ──► voxl-vision-hub ──► PX4 EKF2 ──► position controller (Steps 4, 7, 8) (Steps 3, 5, 9) (Step 6) (Steps 1, 6) (Step 0, 8) The core diagnostic split, straight from ModalAI's docs: if voxl-inspect-vins shows valid, moving position data, VIO is working, and no amount of camera recalibration will help; the problem is on the PX4 side. Use that rule constantly. Quick triage table Symptom Most likely cause Go to Drifts in Manual / Stabilized mode Expected; no position control in that mode Step 0 QGC says "position mode rejected" / falls back to Altitude PX4 not getting or not fusing VIO; outdoor/GPS params loaded Step 1 Position mode accepted, but slow wander VIO quality, environment, calibration Steps 3–5, 7 Position mode accepted, vehicle runs away fast after takeoff Frame/extrinsics mismatch Step 6 Holds OK, then sudden jump/lurch mid-flight VIO reset in flight Step 9 "Bouncing" up and down, oscillating Height source, vibration, tether, or tuning Step 8 VIO stays in INIT on the ground IMU cal, cam cal, texture at takeoff spot Step 9 Step 0 — Confirm which flight mode the drift happens in (2 min) Why first: this single question resolves a large share of reports. Manual mode will drift because it has no position control. Do: Note the mode on the RC mode switch and in QGC at the moment of drift. Manual / Stabilized / Altitude: horizontal drift is expected. Altitude mode holds height only. Only Position (and Offboard) mode uses VIO to hold X/Y. Pass: the drift is happening in Position mode. → Continue. Fail: the drift is in Manual/Altitude. → The fix is to get Position mode working; go to Step 1. Note for the #5505 case: the user also re-ran QGC's sensor calibration hoping to fix drift. That calibrates PX4's flight IMU, which helps attitude, but it does not touch imu_apps, the IMU OpenVINS uses (see Step 7). It also cannot make Manual mode hold position. Step 1 — Is PX4 configured for indoor VIO? (5–10 min, highest-yield check) Why: a ModalAI moderator stated that the Starling 2 Max is marketed as an outdoor drone and ships with "outdoor GPS" PX4 parameters, so its default Position mode tries to use GPS. Indoors with no GPS fix, PX4 then rejects Position mode or flies on a bad estimate. Another Starling 2 Max user's drift was resolved by loading indoor_vio_missing_gps.params. Do: Plug in the battery, wait ~30 s for voxl-vision-hub to start, connect QGC. Flip the mode switch Manual → Position with the props off or disarmed. Listen for QGC's announcement: "position" → PX4 accepts the VIO. "position mode rejected, altitude flight mode" → PX4 isn't getting or isn't fusing VIO. Load the version-matched indoor VIO parameter file from voxl-px4-params (for PX4 v1.14: params/v1.14/EKF2_helpers/indoor_vio.params, or indoor_vio_missing_gps.params if no GPS is attached). In QGC: Parameters → Tools → Load from file, then reboot. Spot-check these parameters afterward: Param Indoor VIO-only value Notes EKF2_EV_CTRL per param file ModalAI calls this the most often overlooked VIO param SYS_HAS_MAG 0 Otherwise PX4 may reject Position mode for want of a magnetometer EKF2_MAG_TYPE 5 Disables mag fusion SYS_HAS_GPS 0 Only if no GPS is on the vehicle EKF2_AID_MASK no longer exists on PX4 1.14; ignore older guides that reference it. Pass: QGC accepts Position mode on the bench. Fail: continue to Steps 2–3 to find out why VIO isn't reaching EKF2. Watch for: params from the wrong PX4 version cause subtle breakage. Also, a connected GPS/mag unit fighting VIO can corrupt local position. For a quick experiment, ModalAI suggests disconnecting it. Step 2 — Are the right services running, and only one VIO engine? (2 min) Do: voxl-version voxl-inspect-services Pass criteria: voxl-camera-server, voxl-open-vins-server, voxl-vision-hub, voxl-px4 are Enabled + Running. voxl-qvio-server is Disabled / Not Running. Only one VIO engine should run at a time. /etc/modalai/voxl-vision-hub.conf has:"vio_pipe": "ov", "secondary_vio_pipe": "", Vehicles set up on older SDKs may still have "vio_pipe": "qvio" with OpenVINS as the fallback. All packages come from one SDK release. Mixed package versions break the pipeline. Prefer flashing a complete SDK over upgrading single packages. Fix if needed: voxl-configure-qvio disable systemctl stop voxl-qvio-server systemctl enable voxl-open-vins-server systemctl restart voxl-open-vins-server voxl-vision-hub Nuclear option: voxl-configure-mpa resets every service config to the SKU defaults. Step 3 — Is VIO healthy on the ground before arming? (2 min) Do: voxl-inspect-vins Read three fields: State: FAIL (0), INIT (1), or OKAY (2). Must be OKAY. Quality: higher is better; -1 = failed. OpenVINS applies hysteresis, so it shouldn't flicker. Error codes: a hex bitfield decoded by the tool. Mostly meaningful when the state is FAIL. The full table is on the Pipe Interface page. Pass: OKAY, stable quality, position near zero and not wandering while the vehicle sits still. Fail: stuck in INIT → Step 9's "won't initialize from rest" list. Wandering while stationary → Steps 4 and 7. Operational rule: ModalAI recommends that if you need VIO from takeoff, you initialize statically on the ground, confirm OKAY, and only then take off. Make "wait for OKAY" part of the preflight. Step 4 — Look at the camera images (5 min) Why: VIO depends on visible features plus low-noise IMU data. Bad imagery is the most common physical cause of drift indoors. Do: open voxl-portal in a browser (drone's IP) and view each tracking camera and the VIO tab. Checklist: Lens covers removed, lenses clean (plastic lens; microfiber only) In focus: for OV7251 fisheye, everything beyond ~15 cm should be sharp (test with high-contrast objects at 15 cm and 1 m) Enough light; no glare or hot spots Texture at both near and far range. A plain lab floor under the down camera, blank walls, or a boundary net filling the view all starve the tracker. Far-only features give orientation but poor position. Nothing intruding into the view (legs, tether, payloads, wiring) Cameras detected: voxl-camera-server -l Also check camera-server health. A Starling 2 Max user on SDK 1.6.3 / OpenVINS 0.6.0 saw massive drift from feature loss. Running voxl-camera-server in the foreground showed repeated Received "Result"/"Buffer" error from camera: tracking_down and dropping frame after re-init. ModalAI's fix was updating OpenVINS to the GitLab master branch (or the synced-timestamp branch for epoch-synced AR0144 tracking cams). To look for this: systemctl stop voxl-camera-server voxl-camera-server # watch for repeated per-frame errors, then Ctrl-C systemctl start voxl-camera-server Fix: add texture (tape patterns, posters, mats on the floor), improve lighting, or move the takeoff spot. ModalAI's guidance is to fix the scene rather than tune the estimator. For the 20' × 30' netted demo area: a uniform floor plus a net perimeter is a weak VIO environment. Put high-contrast texture on the floor under the takeoff point and along the walls the front camera will see. Step 5 — Hand-held test (5 min, props off) This is the definitive "is VIO itself healthy?" test. Repeat it after any VIO config change. Props off, VIO running, VIO tab open in voxl-portal. Slowly lift and move the vehicle about half a meter. Features should stay locked on the same physical points. Features that pop in and out or slide off their targets usually mean wrong camera-to-IMU extrinsics. Walk it around the room and return it to the exact start position and heading. Reported drift should be a few percent of distance traveled, with very small yaw drift. While moving, sanity-check axes in voxl-inspect-vins. Forward should give +X; up should give −Z (FRD/NED). Pass: drift is a few percent and features are locked → VIO is fine. Go to Step 6. Fail: large drift or sliding features → Step 7 (calibration/extrinsics). If calibration checks out → Step 9 logging. Step 6 — Verify the pose that actually reaches PX4 (5 min) Why: VIO can be perfect while the estimate PX4 flies on is wrong, because extrinsics or EKF2 fusion sit in between. A coordinate mismatch makes PX4 take off and then quickly run away out of control. Do: Pose after extrinsics are applied (should match PX4's local position):voxl-inspect-pose vvhub_body_wrt_local Good VIO but wrong pose here → extrinsics problem. Check with voxl-inspect-extrinsics and see Configure Extrinsics. In QGC → Analyze → MAVLink Inspector: ODOMETRY: X/Y non-zero and moving correctly in NED as you carry the drone (forward = +X North-ish in local frame, right = +Y, up = −Z). LOCAL_POSITION_NED: Z updating but X/Y stuck at zero = EKF2 config problem, not VIO. Go back to Step 1. Check camera selection: voxl-inspect-vio-cams (config in /etc/modalai/vio_cams.conf). Pass: VIO pose, vision-hub pose, and PX4 local position all agree and move in the right directions. Step 7 — Calibration (15–60 min) Only do this if Steps 3–6 point at estimation quality. Recalibrating isn't free, and it doesn't help when VIO is already good (see the decision rule at the top). 7a. VIO IMU (imu_apps), not the PX4 IMU The VIO IMU is the apps-processor IMU (imu_apps), not the one PX4 flies on. QGC sensor calibration does not calibrate it. Recalibrate with voxl-calibrate-imu (or from voxl-portal), then confirm gravity reads ≈ 9.81 m/s²:voxl-inspect-imu imu_apps A wrong gravity magnitude or bad biases give a static init that looks fine on the bench and falls apart once airborne. Try removing the IMU temperature-calibration file from /data/modalai/. It's optional and can hurt if captured poorly. Back it up first. 7b. Camera intrinsics Files: /data/modalai/opencv_<pipe>_intrinsics.yml. Resolution in the cal file must match the camera's current streaming resolution. A 640×480 cal is invalid at 1280×800. Check the stored reprojection_error. The ModalAI calibrator accepts ≤ 0.75 px (pinhole) / ≤ 0.60 px (fisheye); recalibrate if you're near the limit. Tracking cameras are factory-calibrated. If you've lost the factory cal, ModalAI keeps production backups; ask on the forum with the board's serial number. 7c. Extrinsics /etc/modalai/extrinsics.conf defines camera/IMU geometry. ModalAI ships these from CAD, so they're accurate but not per-unit calibrated. They only need changing if cameras were moved or the airframe was modified. ️ Documentation discrepancy (calibration threshold): ModalAI's calibrator accepts up to 0.75 px (pinhole) / 0.60 px (fisheye). Upstream OpenVINS says a good calibration has reprojection error under about 0.2–0.5 px. A cal that "passes" ModalAI's gate can still be mediocre by OpenVINS's standard. If you're chasing residual drift, treat anything above ~0.5 px as a recalibration candidate. Step 8 — Mechanical & flight-dynamics confounders (10 min) These make a good estimate look like drift, or degrade it in flight only. Vibration: degrades VIO significantly. Check with:voxl-inspect-vibration and the PX4 log. Fix damping, balance props, and replace damaged props before touching software. Tether / test fixture: the #5505 user is flying tethered to a fixture. A taut tether pulls the vehicle, so the position controller fights it, which can look like "jumping up and down" and drift. It may also intrude into a camera view. Validate VIO with a slack tether, or untethered at low altitude in a netted area. Height "bouncing": check which height source EKF2 uses in the indoor param file you loaded and confirm it actually applied. In a small enclosed room, prop wash and ground effect disturb a barometer. Airframe changes: added payloads, lights, or prop guards affect both vibration and camera view. Step 9 — Initialization & in-flight resets VIO won't initialize from rest (stuck in INIT) ModalAI's ordered list: Recalibrate IMU; confirm ≈ 9.81 m/s² (Step 7a). Camera calibration resolution matches current stream (Step 7b). Lighting/texture at the takeoff spot. Static init doesn't need features, but the filter needs them immediately after. Static vs dynamic init: static needs the vehicle stationary and level-ish. Dynamic needs ~2 s of motion with parallax, which a vehicle sitting still never provides. Vibration / airframe intrusions. Record a log (Step 10). Sudden jump or lurch mid-flight That's likely an auto-reset. The health monitor (30 Hz) resets on estimator-health codes (corrupt covariance, sustained low quality, feature starvation, velocity-uncertainty breaches). Transport warnings such as dropped frames do not trigger resets. A dynamic re-init can produce a jump discontinuity in the estimate, which PX4 will chase. Watch voxl-inspect-vins during a hover for state changes and error codes. If the use case can't tolerate jumps, ModalAI's advice is not to rely on dynamic init or warm resets. Initialize statically on the ground instead. Relevant knobs: en_auto_reset, auto_reset_max_velocity, auto_reset_max_v_cov_timeout_s, auto_reset_min_features, auto_reset_min_feature_timeout_s in /etc/modalai/voxl-open-vins-server.conf; init_dyn_use in estimator_config.yaml. The shipped values are sensible, so change one group at a time and validate with replays. ️ Documentation discrepancy (initialization defaults and where init_dyn_use lives): The Flying with VIO page says Open-VINS "initializes dynamically at any attitude." A 2025 forum reply from ModalAI staff (SDK 1.4.1) says the default config does not use dynamic initialization, and puts init_dyn_use in voxl-open-vins-server.conf. The current Initialization & Resets page puts init_dyn_use in estimator_config.yaml (under the yaml_folder, default /usr/share/modalai/voxl-open-vins/VoxlConfig/starling2) and presents static vs dynamic as an application choice. Behavior has changed across SDK versions. Check init_dyn_use in both files on the actual vehicle rather than trusting any one page, and match it to the SDK reported by voxl-version. Step 10 — Capture data and escalate If you got here without a fix, collect a complete package before posting to the forum. It turns a multi-day back-and-forth into one reply. voxl-version > voxl-version.txt voxl-inspect-services > services.txt cp /etc/modalai/voxl-open-vins-server.conf /etc/modalai/vio_cams.conf /etc/modalai/extrinsics.conf . voxl-logger -b -v ov # record VIO around a failing hover/takeoff PX4 flight log (.ulg adb shell ls /data/px4/log adb pull /data/px4/log/<session>/<log>.ulg . # or: QGC → Analyze → Log Download Upload the .ulg to https://logs.px4.io. The VIO log can be replayed offline with voxl-benchmark-vio. Include: flight mode at time of drift, the hand-held test result, and screenshots of the voxl-portal VIO tab and the QGC ODOMETRY / LOCAL_POSITION_NED inspector. Appendix A — Likely path for forum thread #5505 Based only on what the user posted. Not confirmed. Flew in Manual mode → drift is expected (Step 0). Indoor GPS-denied lab on a Starling 2 Max → very likely still on the factory outdoor/GPS params; load the indoor VIO params (Step 1). This is the single most likely fix. Recalibrated sensors in QGC → doesn't affect imu_apps; if VIO is bad, use voxl-calibrate-imu (Step 7a). Tethered to a fixture, "jumping up and down" → tether loading and/or height source; test with slack tether (Step 8). Demo in a netted 20'×30' room → add floor/wall texture and wait for OKAY before arming (Steps 3–4). Appendix B — Command cheat sheet Purpose Command SDK/package versions voxl-version Service status voxl-inspect-services VIO state/quality/errors voxl-inspect-vins Reset VIO voxl-reset-vins Pose sent to PX4 voxl-inspect-pose vvhub_body_wrt_local VIO camera selection voxl-inspect-vio-cams Extrinsics voxl-inspect-extrinsics Detected cameras voxl-camera-server -l VIO IMU check voxl-inspect-imu imu_apps VIO IMU calibration voxl-calibrate-imu Vibration voxl-inspect-vibration Reset all configs to SKU default voxl-configure-mpa Log VIO for replay voxl-logger -b -v ov Sources ModalAI — Flying with VIO (triage ladder, hand-held test, X/Y-zero rule, IMU and calibration checks, PX4 params) ModalAI — voxl-open-vins-server ModalAI — Initialization & Resets ModalAI — Pipe Interface / error codes ModalAI — voxl-px4-params OpenVINS — Sensor Calibration Forum — #5505 Starling Max 2 arming/drift Forum — Starling 2 Max drifting off (manual mode) Forum — Position Mode Unavailable (outdoor GPS params) Forum — OpenVINS drift from camera-server errors Forum — Problems resetting voxl-open-vins-server Forum — voxl-open-vins-server config (SDK 1.4.1)

It is saying that your throttle is not at lowest position. Is that the case? Can you calibrate the RC in QGC and see all of the sticks moving as expected?

Thank you! Ordering now

Potentially try to register using another email address. Our public files (including CAD files) are located here https://modalai.filecloudonline.com/ui/core/index.html#/

Thanks for sharing this. The details about the Mission Planner reconnect issue and how it affects the VOXL ArduPilot setup were really useful. Hopefully, the troubleshooting discussion here helps others facing something similar.

@sjt277 , I am sorry this happened to you. In order to help evaluate the issue, can you please post photos of both sides of the M0138 ESC board (high resolution, please, you could share a link if the forum does not accept it). Also please point out in the picture which component is getting hot. Also, since you are using a power supply, it should provide the current draw when you attempt to power on the ESC. Please let us know the voltage and current reading on the power supply and whether it is changing. Did the ESC work at first (spinning motors) and then stopped working at some point? Please note that testing ESCs using a power supply often lead to permanent damage due to regenerative spikes when the motor is braking (causing over-voltage). https://docs.modalai.com/voxl-escs/faq/#unboxing-and-testing-new-standalone-esc Alex

Hello @enric-cervera-mateu , Good news: you don't need to install any special ModalAI firmware on the iFlight Commando 8. ModalAI does not provide transmitter firmware — the Commando 8 ships pre-loaded with EdgeTX and a built-in ELRS module, which is exactly what you need to control a VOXL 2 Starling. Here is what you actually need to do: 1. Make sure you have the right frequency variant The Starling V2 ships with a 915 MHz BetaFPV ELRS receiver. You must use a Commando 8 with a matching band: If your drone has the 915 MHz receiver → get the iFlight Commando 8 ELRS 868/915 MHz V2 If your drone has a 2.4 GHz receiver → get the iFlight Commando 8 ELRS 2.4 GHz V2 Mixing bands (e.g., 2.4 GHz TX with 915 MHz RX) will prevent binding entirely. 2. Match ELRS firmware versions The ELRS firmware version on the transmitter module and the receiver must share the same major version (e.g., both on 3.x). Mixing 3.x and 2.x is not supported. Check the TX firmware version in EdgeTX: go to SYS → Hardware → TX Module or the ELRS Lua script. Check the receiver firmware version via the voxl-elrs tool on the drone (see Step 4). If versions don't match, update both using the ExpressLRS Configurator for the TX module, and voxl-elrs for the receiver. 3. Bind the transmitter to the receiver Two methods work with ELRS: Method A — Binding phrase (recommended): Both the TX module and receiver must be flashed with the same binding phrase. If the original controller used a binding phrase, you'll need to reflash the receiver on the drone with a new phrase that matches what you set on the Commando 8. Method B — Button bind: Power on the drone. Within 30 seconds, press and hold the bind button on the ELRS receiver. On the Commando 8, start binding from the ELRS Lua script (Tools menu in EdgeTX). The receiver LED will change when binding succeeds. Power-cycle the drone after binding. (Skipping this step causes "Detected 0 radio channels" errors.) 4. Configure the VOXL 2 software SSH into the VOXL 2 and edit the PX4 configuration file: vi /etc/modalai/voxl-px4.conf Set the RC protocol to CRSF: RC=CRSF_RAW Then restart the PX4 service: systemctl restart voxl-px4 5. Verify RC input After binding and restarting, verify channels are publishing: px4-listener input_rc If no channels appear, check: Power-cycle was done after binding journalctl -b -u voxl-px4 for driver errors Physical wiring on connector J19 (receiver TX → RC_UART_RX, receiver RX → RC_UART_TX, 5V, GND) Wiring reference (J19 on VOXL 2) Receiver pin VOXL 2 J19 pin 5V VDC_5V_LOCAL GND GND TX RC_UART_RX RX RC_UART_TX (needed for voxl-elrs firmware updates) For the full wiring diagram and RC configuration reference, see the official docs: RC Configs: https://docs.modalai.com/voxl2-rc-configs/ voxl-elrs tool: https://docs.modalai.com/voxl-elrs/ If you continue to have binding issues (particularly if the receiver is still bound to the original lost controller), you may need to reflash the receiver to clear the old binding phrase. The voxl-elrs tool can help with this for BetaFPV receivers. Sources https://docs.modalai.com/voxl2-rc-configs/ — VOXL 2 RC controller configuration, wiring, supported protocols https://forum.modalai.com/topic/3066/elrs — ModalAI forum thread on ELRS setup with VOXL 2 Starling https://forum.modalai.com/post/17958 — Forum post on switching Starling 2 from Ghost Atto to ELRS https://shop.iflight.com/Commando8-Radio-Transmitter-ELRS-V2-Pro2092 — iFlight Commando 8 ELRS V2 product page https://github.com/ExpressLRS/ExpressLRS — ExpressLRS project (for Configurator tool)

It's not really a priority for us at the moment but our platform is open and you should be able to adapt Crazyswarm2 to work with PX4. But there are no plans at the moment to design a new drone specifically for that use case.

Thanks Zach — that answers what we needed. We will pick up the newer OpenVINS build separately — we are holding this unit at factory voxl-suite 1.6.4~beta5 for now, since it is the baseline our 22 Sep / 28 Sep comparison rests on. If the 15 Hz state shows up again before then, I will post the journal from that boot here. Thanks again for digging into it — the static-jerk-throttle explanation was the piece we could not have found on our own. JinHyeok

Hi John, No worries, also apologies for the delayed response. I should have asked for the SDK version you are on since we started packaging a voxl-sparrow-utils package that has that mlanutl bin that was missing in a later SDK version, I included the deb in the installer which should hopefully install correctly. Here is the new one to try with the README.MD with the instructions: https://drive.google.com/drive/folders/1SBCSf8_EZkkYV3GnvDhC2poD7ckjDLWq?usp=sharing , Thanks! Luke

@Alex-Kushleyev Hi Alex. Thanks for following up on this topic. I will update this thread with details. Thanks!

Hi @hartll244 , Please see these related posts. https://forum.modalai.com/topic/3664/voxl1-and-2-environmental-testing-documents/7?_=1790881535163 https://forum.modalai.com/topic/5316/need-operating-and-storage-temperature-ranges-for-5-components?_=1790881629795 VOXL 2 Mini falls under VOXL 2 as the core components are the same. Hope this helps you. Thanks!

Hi @marcos-correa Apologies for the delays here, I was out on leave for a couple weeks. It sounds like the M0141 issue you might be having is very similar to this one: https://forum.modalai.com/topic/1356/sentinel-drone-randomly-reboots/2?_=1790714717250 It's important to use 5mm spacers between any VOXL 2 plug-in board, especially if it only picks up J3 and not J5, since that leave all the pins on J5 vulnerable to contacting circuitry from whatever plug-in board is installed. Symptoms from that contact are most certainly proven to be resets and brown outs, as we have seen that before. If you are already using spacers between your board, then I'd need to think about other potential root causes. Hope this helps. Thanks! Vinny

@Nick-Stroumtsos The Zorro Blue does not have any audio capabilities. It is built with custom electronics which do not include support for a speaker so no firmware can enable audio features.

@Zachary-Lowell-0 Thank you for testing it out and for fast response. I am also feeling it is a network issue. I will also try to replicate the same test condition as yours, also will verify the bandwidth. Thanks!

It looks like we have one M10000633 on hand. Reach out to https://modalai.com/contact and see if they can get it to you