Debugging steps for: "Pre-arm Check Failure: Compass Sensor 0 Missing"

[brandon]

Hello,

I've successfully flown my Starling 2 Max maybe 15 times now. Today I powered on the drone and received the status message:

Pre-arm Check Failure: Compass Sensor 0 Missing

I cannot fly the vehicle anymore. Can the engineering team provide some debugging steps to isolate what has failed or is going wrong?

So far I swapped out the GPS unit with a second Starling 2 Max that I have, but the Pre-arm message remains and I cannot fly.

Thank you!

[brandon]

Debugging steps I have done so far:

• Swapped GPS unit with another Starling 2 Max
• Inspected and re-seated connector on both sides (gps, and voxl side)
• Ssh'd into drone and run debugging commands below.

My current hypotheses:

• The cable is broken between the gps and voxl board.
• There is a hardware issue on the voxl board so it isn't sending commands over i2c

Do you have other ideas for things I can try or ideas for what could be wrong?

voxl2:~$ px4-listener sensor_mag
never published
voxl2:~$ px4-listener sensor_gps

TOPIC: sensor_gps
sensor_gps
timestamp: 678990321 (0.088196 seconds ago)
timestamp_sample: 0
time_utc_usec: 1786650062749778
device_id: 11272245 (Type: 0xAC, SERIAL:6 (0x00))
lat: 396691361
lon: -1052411998
alt: 2071371
alt_ellipsoid: 2049863
s_variance_m_s: 0.12200
c_variance_rad: 0.75099
eph: 0.46500
epv: 0.56300
hdop: 0.60000
vdop: 0.86000
noise_per_ms: 95
jamming_indicator: 63
vel_m_s: 0.02500
vel_n_m_s: 0.00600
vel_e_m_s: 0.02500
vel_d_m_s: -0.01500
cog_rad: 6.06156
timestamp_time_relative: 0
heading: nan
heading_offset: 0.00000
heading_accuracy: 0.00000
rtcm_injection_rate: 0.00000
automatic_gain_control: 0
fix_type: 4
jamming_state: 1
spoofing_state: 1
vel_ned_valid: True
satellites_used: 24
selected_rtcm_instance: 0

voxl2:~$ cat /etc/modalai/voxl-px4.conf
#!/bin/bash

voxl-px4 Configuration File

AIRFRAME:

Tell PX4 which AIRFRAME to use.

Options include: [MULTICOPTER, FIXED_WING]

GPS:

Tell PX4 which GPS to use. If there is no GPS unit use NONE. Otherwise

choose AUTODETECT and the startup script will attempt to automatically

configure the GPS, magnetometer, and status LED

Options include: [NONE, AUTODETECT]

RC:

Tell PX4 which RC transmitter to use.

Use EXTERNAL when getting RC control from external Mavlink messages (e.g Via QGC)

Options include: [SPEKTRUM, CRSF_MAV, CRSF_RAW, M0065_SBUS, EXTERNAL, FAKE_RC_INPUT]

ESC:

Tell PX4 which type of ESC to use.

Options include: [VOXL_ESC, VOXL2_IO_PWM_ESC]

POWER_MANAGER:

Tell PX4 which power manager to use.

Use NONE for ModalAI Mini-ESC since the ESC driver handles PM.

Use EXTERNAL when not using the ModalAI APM power manager to power the board

This also just disables the voxlpm driver, same as the NONE option

Options include: [VOXLPM, EXTERNAL, NONE]

AIRSPEED_SENSOR:

Tell PX4 which airspeed sensor peripheral to use.

Note: The sensor will be started on external I2C port on voxl2

Options include: [NONE, MS4525DO]

DISTANCE_SENSOR:

Tell PX4 which distance sensor peripheral to use.

Note: The sensor will be started on the RC port so it is only

really possible to use it when using external RC.

Options include: [NONE, LIGHTWARE_SF000]

OSD:

Tell PX4 whether to enable OSD (on-screen display).

Options include: [ENABLE, DISABLE]

DAEMON_MODE:

Tell PX4 whether to enable daemon mode.

Options include: [ENABLE, DISABLE]

SENSOR_CAL:

Tell PX4 where to source sensor calibration information.

Options include: [ACTUAL, FAKE]

ARTIFACT_MODE:

Do not allow artifacts to be saved to disk. Will not start the logging

module, will delete any current log files, and will delete the data manager file.

Options include: [ENABLE, DISABLE]

EXTRA_STEPS:

Optional field that allows a user to define custom commands to be run by PX4 on boot.

Must be a valid bash array as seen below

Example: EXTRA_STEPS=( "qshell gps start" "qshell commander mode manual" )

AIRFRAME=MULTICOPTER
GPS=AUTODETECT
RC=GHST
ESC=VOXL_ESC
POWER_MANAGER=NONE
AIRSPEED_SENSOR=NONE
DISTANCE_SENSOR=NONE
OSD=DISABLE
DAEMON_MODE=ENABLE
SENSOR_CAL=ACTUAL
ARTIFACT_MODE=DISABLE
EXTRA_STEPS=()

voxl2:~$ voxl-version
────────────────────────────────────────────────────────────────────────────────
system-image: 1.8.06-M0054-14.1a-perf
kernel: #1 SMP PREEMPT Wed Oct 22 04:13:18 UTC 2025 4.19.125
────────────────────────────────────────────────────────────────────────────────
hw platform: M0054
mach.var: 1.0.1
SKU: MRB-D0012-4-V2-C29-T9-M28-X0
────────────────────────────────────────────────────────────────────────────────
voxl-suite: 1.6.3
────────────────────────────────────────────────────────────────────────────────
Packages:
Repo: http://voxl-packages.modalai.com/ ./dists/qrb5165/sdk-1.6/binary-arm64/
Last Updated: 2026-07-29 21:29:05
WARNING: repo file has changed since last update,
packages may have originated from a different repo
List:
libfc-sensor 1.0.9
libmodal-cv 0.6.0
libmodal-exposure 0.1.4
libmodal-flow 1.0.3
libmodal-journal 0.2.7
libmodal-json 0.4.8
libmodal-pipe 2.14.11
libqrb5165-io 0.6.3
libvoxl-cci-direct 0.3.3
libvoxl-codec 0.0.2
libvoxl-cutils 0.1.6
modalai-slpi 1.2.2
mv-voxl 0.1-r0
qrb5165-bind 0.1-r0
qrb5165-dfs-server 0.2.0
qrb5165-mini-tof-server 0.2.2
qrb5165-rangefinder-server 0.1.6
qrb5165-slpi-test-sig 01-r0
qrb5165-tflite 2.17.2
voxl-bind-spektrum 0.1.1
voxl-camera-calibration 0.6.1
voxl-camera-server 2.2.19
voxl-ceres-solver 2:2.0.0-2
voxl-configurator 1.1.5
voxl-cpu-monitor 0.7.7
voxl-docker-support 1.3.1
voxl-elrs 1.1.0
voxl-esc 1.5.7
voxl-esptool 0.2.0
voxl-feature-tracker 0.5.2
voxl-flow-server 0.3.6
voxl-gphoto2-server 0.0.10
voxl-imu-server 2.0.1
voxl-io-server 0.0.8
voxl-jpeg-turbo 2.1.3-7
voxl-lepton-server 1.3.3
voxl-lepton-tracker 0.0.4
voxl-libgeographic 1.0.0
voxl-libgphoto2 0.0.4
voxl-libuvc 1.0.7
voxl-logger 0.6.1
voxl-mavcam-manager 0.6.0
voxl-mavlink 0.1.6
voxl-mavlink-server 1.4.14
voxl-modem 1.2.3
voxl-mongoose 7.19.0
voxl-mpa-to-ros 0.3.9
voxl-mpa-tools 1.5.6
voxl-nano-tracker 0.1.7
voxl-open-vins-server 0.6.0
voxl-opencv 4.5.5-3
voxl-osd 0.3.8
voxl-portal 0.8.7
voxl-px4 1.14.0-2.0.133
voxl-px4-params 0.9.0
voxl-qvio-server 1.2.3
voxl-remote-id 0.0.9
voxl-reset-slpi 0.0.1
voxl-state-estimator 0.0.6
voxl-streamer 0.8.0
voxl-suite 1.6.3
voxl-tag-detector 0.1.0
voxl-tflite-server 0.5.1
voxl-utils 2.0.2
voxl-uvc-server 0.1.7
voxl-vision-hub 1.9.21
voxl-vtx 2.0.2
voxl-wavemux 0.0.3
voxl2-io 0.0.3
voxl2-security-hardening-utls 1.0-r0
voxl2-system-image 1.8.06-r0
voxl2-wlan 1.0-r0
────────────────────────────────────────────────────────────────────────────────
voxl2:~$

voxl2:~$ px4-qshell
voxl2:~$

voxl2:~$ ist8310 status
-bash: ist8310: command not found

voxl2:~$ px4-qshell ist8310 status
INFO [qshell] Send cmd: 'ist8310 status'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 766401772, local time: 766406205
ERROR [qshell] Command failed
voxl2:~$

voxl2:~$ grep -i -n -E "mag|ist|qmc|gps" /usr/bin/voxl-px4-start
8:echo "GPS: $GPS"
13:echo "DISTANCE SENSOR: $DISTANCE_SENSOR"
119:# Auto detect the magnetometer. If one or both of these devices
122:/bin/echo "Looking for qmc5883l magnetometer"
123:qshell qmc5883l start -R 10 -X -b 1
124:/bin/echo "Looking for ist8310 magnetometer"
125:qshell ist8310 start -R 10 -X -b 1
126:/bin/echo "Looking for ist8308 magnetometer"
128:qshell ist8308 start -R 12 -X -b 1
129:/bin/echo "Looking for iis2mdc magnetometer"
133:# GPS and magnetometer
134:if [ "$GPS" != "NONE" ]; then
136: gps start -d /dev/ttyHS7
138: qshell gps start
200:if [ "$DISTANCE_SENSOR" == "LIGHTWARE_SF000" ]; then
214:# Optional distance sensor on spare i2c
307: # Also remove the data manager file that may have saved GPS waypoint information

voxl2:~$ px4-qshell qmc5883l status
INFO [qshell] Send cmd: 'qmc5883l status'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 948521138, local time: 948523611
ERROR [qshell] Command failed

voxl2:~$ px4-qshell ist8310 status
INFO [qshell] Send cmd: 'ist8310 status'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 961731054, local time: 961733319
ERROR [qshell] Command failed
voxl2:~$

voxl2:~$ px4-qshell ist8310 start -R 10 -X -b 1
INFO [qshell] Send cmd: 'ist8310 start -R 10 -X -b 1'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 973342325, local time: 973345077
ERROR [qshell] Command failed

voxl2:~$ px4-qshell ist8310 status
INFO [qshell] Send cmd: 'ist8310 status'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 989255823, local time: 989257867
ERROR [qshell] Command failed
voxl2:~$ px4-listener sensor_mag
never published

voxl2:~$ px4-qshell qmc5883l start -R 10 -X -b 1
INFO [qshell] Send cmd: 'qmc5883l start -R 10 -X -b 1'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 1009230646, local time: 1009233503
ERROR [qshell] Command failed
voxl2:~$
voxl2:~$ px4-qshell qmc5883l status
INFO [qshell] Send cmd: 'qmc5883l status'
INFO [qshell] cmd returned with: -1
INFO [qshell] qshell return value timestamp: 1009321642, local time: 1009323539
ERROR [qshell] Command failed
voxl2:~$
voxl2:~$ px4-listener sensor_mag
never published

voxl2:~$ journalctl -u voxl-px4 -b | grep -i -E "mag|ist|qmc|i2c|gps"
Aug 13 13:54:30 m0054 voxl-px4[2464]: GPS=AUTODETECT
Aug 13 13:54:30 m0054 voxl-px4[2464]: DISTANCE SENSOR=NONE
Aug 13 13:54:30 m0054 voxl-px4[2464]: GPS: AUTODETECT
Aug 13 13:54:30 m0054 voxl-px4[2464]: DISTANCE SENSOR: NONE
Aug 13 13:54:33 m0054 voxl-px4[2464]: WARN [SPI_I2C] UnknownApp: no instance started (no device on bus?)
Aug 13 13:54:33 m0054 voxl-px4[2464]: WARN [SPI_I2C] UnknownApp: no instance started (no device on bus?)
Aug 13 13:54:33 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Register interrupt b214f094 e612f13c b2602648
Aug 13 13:54:33 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0xb76329 12018473
Aug 13 13:54:33 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 5
Aug 13 13:54:33 m0054 voxl-px4[2464]: INFO [muorb] icp101xx #0 on I2C bus 5
Aug 13 13:54:34 m0054 voxl-px4[2464]: Looking for qmc5883l magnetometer
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [qshell] Send cmd: 'qmc5883l start -R 10 -X -b 1'
Aug 13 13:54:34 m0054 voxl-px4[2464]: Looking for ist8310 magnetometer
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [qshell] Send cmd: 'ist8310 start -R 10 -X -b 1'
Aug 13 13:54:34 m0054 voxl-px4[2464]: Looking for ist8308 magnetometer
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [qshell] Send cmd: 'ist8308 start -R 12 -X -b 1'
Aug 13 13:54:34 m0054 voxl-px4[2464]: Looking for iis2mdc magnetometer
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [qshell] Send cmd: 'gps start'
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: qmc5883l start -R 10 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'qmc5883l'
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0x80d09 527625
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: qmc5883l start -R 10 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: ist8310 start -R 10 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'ist8310'
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0x60e09 396809
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: ist8310 start -R 10 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: ist8308 start -R 12 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'ist8308'
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0xb0c09 723977
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: ist8308 start -R 12 -X -b 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0xe1e09 925193
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: gps start
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'gps'
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [tasks] Creating pthread gps
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [tasks] Successfully created px4 task PX4_gps with tid 2097644
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [qshell] Ok executing command: gps start
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [gps] GPS UART baudrate set to 115200
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0x7b3809 8075273
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set i2c address 0x38, fd 5
Aug 13 13:54:34 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 13:54:34 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 13:54:35 m0054 voxl-px4[2464]: INFO [uORB] Advertising remote topic vehicle_gps_position
Aug 13 13:54:35 m0054 voxl-px4[2464]: INFO [uORB] Advertising remote topic vehicle_magnetometer
Aug 13 13:54:35 m0054 voxl-px4[2464]: INFO [uORB] Advertising remote topic sensor_preflight_mag
Aug 13 13:54:36 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox firmware version: SPG 5.10
Aug 13 13:54:36 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox protocol version: 34.10
Aug 13 13:54:36 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox module: MAX-M10S
Aug 13 13:54:36 m0054 voxl-px4[2464]: INFO [muorb] [gps] GPS UART baudrate set to 115200
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [uORB] Advertising remote topic obstacle_distance
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [uORB] Advertising remote topic distance_sensor
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] GPS UART baudrate set to 9600
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] GPS UART baudrate set to 38400
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] Got ack to initial CFG_VALSET!
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox firmware version: SPG 5.10
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox protocol version: 34.10
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [muorb] [gps] u-blox module: MAX-M10S
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [uORB] Advertising remote topic sensor_gps
Aug 13 13:55:06 m0054 voxl-px4[2464]: INFO [uORB] Advertising remote topic estimator_gps_status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: ist8310 status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'ist8310'
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] Not running
Aug 13 14:10:33 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: ist8310 status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [health_and_arming_checks] Preflight: GPS Horizontal Pos Drift too high
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: qmc5883l status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'qmc5883l'
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] Not running
Aug 13 14:10:33 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: qmc5883l status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [health_and_arming_checks] Preflight: GPS Horizontal Pos Drift too high
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: ist8310 status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'ist8310'
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] Not running
Aug 13 14:10:33 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: ist8310 status
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] qshell gotten: ist8310 start -R 10 -X -b 1
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [qshell] arg0 = 'ist8310'
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] *** I2C Device ID 0x60e09 396809
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [drivers__device] Set up I2C bus mutex for bus 1
Aug 13 14:10:33 m0054 voxl-px4[2464]: ERROR [muorb] [drivers__device] i2c probe failed
Aug 13 14:10:33 m0054 voxl-px4[2464]: INFO [muorb] [SPI_I2C] PX4_qshell: no instance started (no device on bus?)
Aug 13 14:10:33 m0054 voxl-px4[2464]: ERROR [muorb] [qshell] Failed to execute command: ist8310 start -R 10 -X -b 1
voxl2:~$

[brandon]

[Eric Katzfey]

Can you plug the cable from the working drone into the other one? That could tell you if it's the cable.