Starling 2 Max no GPS data
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@ROBERT-JUDD , the open sky result looks good, so the gps receiver seems just fine.
Now, as a next test, to confirm that interference is coming from the drone (and see what level of interference), make sure that you are getting similar results as you just shown while drone is off and while your u-center is running, turn on the drone and you will likely observe the signal drop as the drone boots up (which may vary over time).
I am curious what that looks like (initial drop when you first power on the drone and then steady state (after 5-10 seconds).
Also, it seems you may have a 5G modem on the Starling 2 Max (if i am not mistaken), please try to see if disabling it will help with the GPS signal. Perhaps certain settings of the 5G modem are affecting GPS signal.
Alex
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@Alex-Kushleyev OK I will try that tomorrow and let you know.
Yes, I do have a 5G Sierra Wireless EM9291 modem active and connected via Google Fi. If I execute “systemctl disable voxl-modem” do I need to reboot for that to take effect? And does that actually remove power from the modem board? Any other modem commands I should try?
Thanks very much for your help.
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@Alex-Kushleyev This morning I could not get the GPS to communicate reliably with my PC - the serial data connection kept fading in and out. I checked all the wiring, made a new cable, and tried a second PC, but the serial connection kept fading in and out. Maybe the GPS module was defective the whole time. Can you tell me how I can get a replacement GPS module? Here are the pics.
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@ROBERT-JUDD , please contact https://www.modalai.com/pages/rma for any replacements you need.
From the picture you posted, i see a big scratch on the antenna, which seems to be deep enough to break up the conductive plane. I am not an antenna expert, but i believe that damage like this will affect the antenna characteristics.
By the way the two notches on the antenna (at 12 and 3 o'clock) are done at the factory when the antennas are fine tuned to the exact frequency. The scratch could throw off the tuning.
Regarding serial connection, sometimes you need to switch your gps receiver to a higher baud rate, otherwise the port will overflow at the default 9600 baud. Please double check. You can send a special command using u center to switch the receiver to a higher baud rate and then autodetect or manually specify the new baud rate in ucenter for the serial connection. I typically always switch to at least 115200 or 230400 first then do my testing.
Regarding disabling the modem, I will ask my colleagues if there is a SW command to power it down.
Alex
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In order to power down the 5G card on M0090, the easiest way to do it is to set VOXL2 GPIO 1 to low. This signal controls the
FULL_CARD_POWER_OFFinput into the 5G card.voxl-gpio -m 1 out voxl-gpio -w 1 0 # power off voxl-gpio -w 1 1 # power on -
@Alex-Kushleyev This is very helpful information, thanks very much for sending. I will follow your recommendations and keep you updated.
FYI I also noticed the antenna scratch in the photo, but I honestly have no idea how that happened. I was very careful handling the GPS module. Maybe it overheated, but I ran a fan over the drone at all times during bench testing and monitored temps via “voxl-inspect-cpu”, so that doesn’t seem likely to me.
Thanks again for your help.
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@Alex-Kushleyev Thanks for the tip regarding serial baud rate, I set it to 115200 as shown below and regained the good satellite data. Then I ran the tests you suggested. The three graphs below are: 1) drone power off; 2) drone power on; and 3) drone power on but 5G card off as per your instructions (voxl-gpio -m 1 out; voxl-gpio -w 1 0).
My impression is that the GPS signal drops considerably when the drone is powered up (first vs second graph below), but that powering off the 5G card had no apparent effect (third graph). Do you agree? Are there any other gpio commands I can use to remove power to various subsystems to search for the source of interference?
I ordered a new GPS module directly from 3DR, it should arrive Monday. I agree that may work better due to the scratch in the current antenna.
Thanks again for your help.
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@ROBERT-JUDD , yes it seems the signal drops by at least 10dB across all the satellites when the drone is switched on. This is quite significant (not good). You most likely would not be able to fly using GPS with these signal levels even though you have a lock (position and velocity estimates would be noisy).
Let me check with the team what the expected signal level is when a properly working Starling 2 Max is receiving GPS.
Alex
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@Alex-Kushleyev sounds good thank you. Overall I really like what your company is doing and I’m happy to run whatever tests would be helpful to identifying strategies to improve drone performance. My main goal is to systematically explore 5G as the sole data link in anticipation of the FAA allowing BVLOS.
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@Alex-Kushleyev Is there a programmatic way to cut power to one or more of the cameras? I have four: front/down hires and front/down tracking. The two downward-facing cameras are mounted immediately adjacent to the GPS module. It would be interesting to see happens to the GPS signal when those cameras are powered on and off.
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@ROBERT-JUDD , when you stop voxl camera server, all the cameras are powered off.
Systemctl stop voxl-camera-server
To disable individual cameras, you can modify /etc/modalai/voxl-camera-server.conf to set the “enabled” parameter to false for the desired camera(s) and restart camera server : systemctl restart voxl-camera-server
Alex
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@Alex-Kushleyev OK, just now I repeated the test of GPS signal with/without powering up the drone and the results were the same as yesterday: roughly 10 dB drop in GPS signal when drone is powered up. At that point I shut down the voxl-camera-server (systemctl stop voxl-camera-server), meaning no power to any cameras, and there was no apparent change (still 10 dB down). I did double check that the change happened via "voxl-inspect-services" (camera server not running).
So here is the current status:
With GPS module connected to u-center2 (not connected to drone but physically in the same position on drone frame):
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Everything below is Lepton connector removed and ALFA USB wifi removed
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Drone powered off: good GPS signal (14-20 satellites tracked, most 40-45 dB)
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Drone powered on: GPS signal drops about 10 dB
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Drone powered on, 5G modem powered off: no improvement
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Drone powered on, 5G modem powered on, all cameras powered off: no improvement
Any other subsystems I can power down and/or unplug? I'll try the new GPS module when it arrives hopefully Monday.
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@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.
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@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!
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Hi @ROBERT-JUDD , my colleague is setting up the exact test with Starling 2 Max with the 5G modem to see if there is any possible interference. We will get back to you soon. Meanwhile, please let us know if swapping of the GPS module produces any positive results. Thank you!
Alex
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@Alex-Kushleyev will do, thanks!
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@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.
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Hi @ROBERT-JUDD,
We are actively testing to find a solution (including myself, I just got my hands on a Starling 2 Max a few days ago and was able to confirm similar SNR to what you have experienced - my drone is without 5G modem). My colleague is testing one with a 5G modem. We acknowledge that there is an issue and we are working on a short-term workaround and a longer term solution.
We understand that this can be concerning and if you are not able to wait for a solution, please reach out to https://www.modalai.com/pages/rma and we can work on a return / refund.
If you are able to work with us on this issues, we are trying out different options including different gps units, disabling different components to find the source of the interference, and also re-locating the position of the gps unit to help reduce the effect of the noise. My gut feeling is that elevating the GPS receiver on a lightweight but rigid mast (4-6in) above the drone and include some shielding right below the receiver should significantly improve the performance (as a short-term workaround). I will test this ASAP and provide the results and pictures). Please give me a few more days.
Alex
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@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!
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Sounds good. Please keep in mind that if you relocate the gps receiver, you should update the offsets for gps sensor position in px4 (prior to flight)
My test will be putting a 4-6in mast either where the gps receiver is now (in the back) or right in the middle, on top of the “roll cage”.
Alex
