ModalAI Support,

I received a new Starling 2 Max a few days ago, and overall it's great, but I'm having a problem with GPS. Basically, the drone appears to NEVER receive any GPS signals even when left outside for long periods of time. My system info and results of px4-listener are pasted below.

This issue appears similar to these other forum discussions, where they seem to think the problem relates to EMI:

https://forum.modalai.com/topic/3879/gps-not-working-for-starling-2-max/16

https://forum.modalai.com/topic/3912/problem-acquiring-gps-satellites-possible-voxl2-board-emi?_=1731073406011

I did unplug the Lepton 8-pin JST SH connector as suggested by James Strawson in the forum discussions above, but that had no effect. I also powered down the WiFI as suggested by Alex Kushleyev, but this also had no effect, although kind of a bad test for me because I couldn't put the drone outside due to USB cable length:

• pin GPIO_157 controls VBUS, which is USB power on VOXL2
• to disable, run voxl-gpio write 157 0
• to enable, run voxl-gpio write 157 1

What do you think I should do next? Is there some way to turn the power off to various subsystems via software in an attempt to figure out if and where EMI is the problem? Any other ideas?

Thanks for your help !

Starling 2 Max Outdoor GPS-denied Development Drone × 1
with Battery Pack and Controller and Case
Dual 4k & Dual Tracking & ToF (C29)
5G WiFi and Ghost Atto 2.4GHz
ECCN: EAR99, NLR

system-image: 1.8.02-M0054-14.1a-perf
kernel: #1 SMP PREEMPT Mon Nov 11 22:47:44 UTC 2024 4.19.125
hw platform: M0054
mach.var: 1.0.1
voxl-suite: 1.4.1
current IP: wlan0: 10.0.0.19

voxl2:~$ px4-listener sensor_gps

TOPIC: sensor_gps
sensor_gps
timestamp: 841732144 (0.020669 seconds ago)
timestamp_sample: 0
time_utc_usec: 0
device_id: 11272245 (Type: 0xAC, SERIAL:6 (0x00))
lat: 0
lon: 0
alt: -17000
alt_ellipsoid: 0
s_variance_m_s: 999.00006
c_variance_rad: 3.14159
eph: 4294967.50000
epv: 3796926.25000
hdop: 99.99000
vdop: 99.99000
noise_per_ms: 64
jamming_indicator: 15
vel_m_s: 0.00000
vel_n_m_s: 0.00000
vel_e_m_s: 0.00000
vel_d_m_s: 0.00000
cog_rad: 0.00000
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: 0
jamming_state: 0
spoofing_state: 1
vel_ned_valid: False
satellites_used: 0
selected_rtcm_instance: 0

voxl2:~$ px4-listener sensor_mag

TOPIC: sensor_mag
sensor_mag
timestamp: 861420482 (0.006257 seconds ago)
timestamp_sample: 861420007 (475 us before timestamp)
device_id: 527625 (Type: 0x08, I2C:1 (0x0D))
x: -0.04417
y: -0.32142
z: 0.42167
temperature: nan
error_count: 0
voxl2:~$

@Alex-Kushleyev Thanks for the update. I had to pivot away from this project and plan to revisit it when ModalAI has a long term fix. Have your colleagues made any progress identifying the source of the EMI?

Thanks again for your help.

@Alex-Kushleyev Did you have a test flight yet? How did the GPS perform while flying?

Thanks

@Alex-Kushleyev Very interesting, thanks for the update.

Regarding the EMI from the Commando 8 transmitter, I wonder what would happen if you removed the Ghost Atto receiver and antenna from the drone. Maybe somehow they are involved in the EMI.

Noise from the 6-conductor cable is also interesting, I wonder if passing them through an RF shield would make a difference.

Please let me know the results of your test flight. If it's successful I may do something similar and repeat your testing.

What ideas do you and your team have for a long term solution? Do you have access to something like SignalHound equipment to search for the source of EMI?

Thanks
Bob

@Alex-Kushleyev Have you made any progress with this yet? Please let me know if/how I can help.

@Alex-Kushleyev Got it, thanks. FYI here's an interesting graph regarding the frequency of the EMI from a prior post:

https://forum.modalai.com/topic/3912/problem-acquiring-gps-satellites-possible-voxl2-board-emi

@Alex-Kushleyev Thanks for the reply, and yes, I'm happy to work with you to find a solution. As an attempt to improve SNR, I took the STEP files and created a "stretched" 3D-printed version of the GPS mount, see below, but I haven't had a chance to install it yet. Based on some previous testing I think the added distance will improve SNR somewhat, and adding some shielding should also help, but I think the best long term solution would be to find the source of EMI and target that. I don't have the equipment or knowledge to do that, however.

Please keep me posted, and let me know if there's any way I can contribute. Thanks for your help!

@Alex-Kushleyev Here are the results of testing with a brand new GPS from a different manufacturer (https://holybro.com/products/micro-m10-gps?variant=42981482954941). The GPS is in the same position as the original, but connected to u-center. As with prior tests, Lepton is disconnected and ALFA is removed.

Top u-center screen shot is with drone powered OFF, bottom is drone powered ON. To me this Holybro GPS looks about the same as the 3DR GPS, i.e. satellite signals drop significantly with drone powered ON. Not shown are results where I found that the satellite signal increased significantly when I moved the GPS module farther away and/or added shielding.

What do you suggest as next steps?

Thanks for your help.

@Alex-Kushleyev will do, thanks!

@Alex-Kushleyev said in Starling 2 Max no GPS data:

Let me check with the team what the expected signal level is when a properly working Starling 2 Max is receiving GPS.

Have you had a chance to check on this?

FYI in the meantime I've purchased 3 additional GPS modules from different manufacturers, and will evaluate them using u-center and the drone when they arrive.

I need to get this problem fixed somehow - can't fly far without a GPS!

@Alex-Kushleyev 3DR says the replacement GPS won't be shipped until next week. Are there any useful tests I can run while waiting, eg. power down selective subsystems and observe GPS signal via u-center? I did hold the current (potentially defective) GPS module in my hand and move it around the drone while observing signal strength in u-center, but it wasn't clear to me where the interference was originating from. Open to suggestions. Thanks for your help.