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    Poor GPS Fix

    PX4 Autonomy Developer Kit
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    • S
      somalley
      last edited by

      Re: GPS and VL53L1 not working

      I'm having a similar issue with my PX4 Autonomy Developer Kit drone. A couple weeks ago, I took my drone out for a flight test and it never acquired any GPS satellites. Today I took it out to a parking lot with minimal sky obstructions and played around with the settings in QGC to see if I could get anything to track. The best I observed through the MavLink telemetry was the track of two satellites with valid PRN and SN values. I let the drone stay powered on for 15-30 minutes after various changes to allow time for the drone to self-download almanac (if it actually does it). Time does not seem to help at all.

      Any help or insight would be appreciated!

      When the drone boots up, here's the INFO that prints out from it:

      [uORB] Advertising remote topic event
      INFO [uORB] Advertising remote topic health_report
      INFO [uORB] Advertising remote topic failsafe_flags
      INFO [uORB] Advertising remote topic actuator_armed
      INFO [uORB] Advertising remote topic vehicle_control_mode
      INFO [uORB] Advertising remote topic vehicle_thrust_setpoint
      INFO [uORB] Advertising remote topic vehicle_torque_setpoint
      INFO [uORB] Advertising remote topic vehicle_status
      INFO [uORB] Advertising remote topic failure_detector_status
      INFO [uORB] Advertising remote topic vehicle_attitude_setpoint
      INFO [uORB] Advertising remote topic vehicle_rates_setpoint
      INFO [muorb] [uORB] Marking DeviceNode(qshell_req) as advertised in process_remote_topic
      INFO [muorb] [qshell] qshell gotten: flight_mode_manager start
      INFO [muorb] [qshell] arg0 = 'flight_mode_manager'
      INFO [muorb] [qshell] arg1 = 'start'
      INFO [uORB] Advertising remote topic vehicle_command
      INFO [muorb] [qshell] Ok executing command: flight_mode_manager start
      INFO [dataman] data manager file '/data/px4/dataman' size is 7866640 bytes
      INFO [muorb] [uORB] Advertising remote topic transponder_report
      INFO [muorb] [uORB] Advertising remote topic rtl_time_estimate
      INFO [muorb] [uORB] Advertising remote topic position_setpoint_triplet
      INFO [mavlink] mode: Onboard, data rate: 100000 B/s on udp port 14556 remote port 14557
      INFO [muorb] [uORB] Advertising remote topic telemetry_status
      INFO [mavlink] partner IP: 127.0.0.1
      INFO [muorb] [uORB] Advertising remote topic obstacle_distance
      INFO [muorb] [uORB] Advertising remote topic vehicle_visual_odometry
      INFO [muorb] [uORB] Advertising remote topic distance_sensor
      INFO [muorb] [uORB] Advertising remote topic offboard_control_mode
      INFO [muorb] [uORB] Advertising remote topic timesync_status
      INFO [uORB] Advertising remote topic estimator_aid_src_rng_hgt
      INFO [muorb] [uORB] Marking DeviceNode(vehicle_command_ack) as advertised in process_remote_topic
      INFO [mavlink] mode: Normal, data rate: 100000 B/s on udp port 14558 remote port 14559
      INFO [muorb] [uORB] Marking DeviceNode(telemetry_status) as advertised in process_remote_topic
      INFO [uORB] Advertising remote topic actuator_controls_status_0
      INFO [px4] Startup script returned successfully
      INFO [logger] logger started (mode=all)
      ERROR [muorb] [ekf2] ====> GLOBAL R to Earth: -152.495228 (42)
      INFO [uORB] Advertising remote topic estimator_aid_src_ev_hgt
      INFO [uORB] Advertising remote topic estimator_aid_src_ev_pos
      INFO [uORB] Advertising remote topic estimator_aid_src_ev_vel
      INFO [uORB] Advertising remote topic estimator_aid_src_ev_yaw
      ERROR [muorb] [gps] GPS: failed to set baud rate 19200 on serial port
      INFO [mavlink] partner IP: 127.0.0.1
      INFO [muorb] [uORB] Marking DeviceNode(vehicle_command_ack) as advertised in process_remote_topic
      INFO [muorb] [gps] No COM port detected
      INFO [muorb] [gps] GPS UART baudrate set to 115200
      INFO [muorb] [uORB] Advertising remote topic ping
      INFO [muorb] [gps] GPS UART baudrate set to 9600
      INFO [muorb] [gps] GPS UART baudrate set to 38400
      INFO [muorb] [gps] Got ack to initial CFG_VALSET!
      INFO [muorb] [gps] u-blox firmware version: SPG 5.10
      INFO [muorb] [gps] u-blox protocol version: 34.10
      INFO [muorb] [gps] u-blox module: MAX-M10S
      INFO [uORB] Advertising remote topic sensor_gps
      INFO [uORB] Advertising remote topic satellite_info
      INFO [uORB] Advertising remote topic mavlink_log

      And here is the voxl-px4 config file. The "EXTRA_STEPS" were added in after the fact while troubleshooting.
      AIRFRAME=MULTICOPTER
      GPS=AUTODETECT
      RC=CRSF_RAW
      ESC=VOXL_ESC
      POWER_MANAGER=VOXLPM
      AIRSPEED_SENSOR=NONE
      DISTANCE_SENSOR=NONE
      OSD=DISABLE
      DAEMON_MODE=ENABLE
      SENSOR_CAL=ACTUAL
      ARTIFACT_MODE=DISABLE
      EXTRA_STEPS=(
      qshell gps start -d 7 -b 115200
      )

      The drone is fairly new and the only "changes" made to it, outside of the GPS QGC settings I played around with, were by the direction of the bootcamp.

      QGC GPS Settings Modified:
      GPS_1_GNSS: 0* and 1
      GPS_1_PROTOCOL: Auto Detect* and U-BLOX
      GPS_SAT_INFO: ENABLED* and DISABLED
      GPS_UBX_BAUD2: 230400, 115200*, 38400

      The configuration that got me two valid PRNs tracking have the * next to them.

      And finally, here's a parse of the .ulg from the original test.
      https://review.px4.io/plot_app?log=37983558-9d8c-4b27-b33e-84373301fca4

      The drone was started in Position mode, it appears that VIO was working fine and holding the drone in place until the altitude was increase beyond what the tracking camera could handle, fell back to altitude hold mode and started flying out of control. We did have a teather on it (just incase) so were able to reel it in and not lose it. Significant wind did pick up halfway through the flight, so I will attribute some of the chaos to that factor.

      1 Reply Last reply Reply Quote 0
      • S
        somalley
        last edited by

        https://forum.modalai.com/topic/4226/starling-2-max-no-gps-data

        Just found this discussion and is likely the cause for my problems considering the two satellites I did track were right above me and still had very low SNR levels (20's). This seems like a pretty bad design flaw that should have been caught in testing. I'm going to try some testing and experimentation on my end to try and mitigate the EMI and will report back with any results that appear promising.

        1 Reply Last reply Reply Quote 0
        • S
          somalley
          last edited by

          Building upon what @ROBERT-JUDD did in his testing, we made a shield out of a tinfoil solder cup to isolate the GPS antenna from the rest of the drone. This resulted in an almost immediate track of 10+ satellites. The EMI problem is real. We are now working on designing a 3D printable cone similar to what the cup is doing that we plan to paint with an EMI coating that will be our more rugged long term solution.

          a48df815-fe02-4080-8114-76ec6b9df44a-image.png

          35c86c5e-015f-4eb2-b412-f5642441dd39-image.png

          d7a15fd8-2730-43f0-a0ec-3430882a0f0c-image.png

          ModalAi should be providing clear disclaimers about this problem before people go and spend thousands on this drone!

          ROBERT JUDDR 1 Reply Last reply Reply Quote 0
          • ROBERT JUDDR
            ROBERT JUDD @somalley
            last edited by

            @somalley @Alex-Kushleyev Thanks for referring to my March 1, 2025 post regarding the GPS problem:

            https://forum.modalai.com/topic/4226/starling-2-max-no-gps-data

            Overall I'm a big fan of ModalAI, but in my opinion this product contains a fundamental design flaw (complete loss of GPS position data due to EMI) that should have been detected and corrected early in the design testing phase. Moreover, that fatal design flaw has remained uncorrected for many months now, and I have received no information about if/when a permanent fix will be available. Our company spent over $5,000 on a Starling 2 Max, and it remains largely unusable due to this problem.

            Alex Kushleyev at ModalAI has in general been very responsive, and has developed a temporary fix that customers can implement on their own, which I genuinely appreciate. But the fact remains that ModalAI inexcusably sold a product with a fundamental design flaw, and has not offered a permanent fix for many months now. In my opinion, at this point a permanent fix should be one of ModalAI's highest priority if they want to avoid a significant loss of customer confidence.

            I would suggest that, as a first step, ModalAI should create a new post dedicated to providing ongoing fix updates and timelines, and to systematically update that post on the same day and time each week until a permanent fix is made available.

            Thank you for your consideration.

            Robert Judd

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