Posts made by ROBERT JUDD

@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.

@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):

0. Everything below is Lepton connector removed and ALFA USB wifi removed

1. Drone powered off: good GPS signal (14-20 satellites tracked, most 40-45 dB)

2. Drone powered on: GPS signal drops about 10 dB

3. Drone powered on, 5G modem powered off: no improvement

4. 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.

@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.

@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.

@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.

@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.

@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.

@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.

@Alex-Kushleyev The previous screen shot was not open sky because I didn't have a USB extension cable, which I bought today. Here is the open sky result. What do you think I should do next? Thanks

@Alex-Kushleyev I'm hoping you or someone at ModalAI will get back to me ASAP about this because frankly I'm getting very frustrated. I added the shield below and I do get a GPS fix, but the quality is poor and when flying it is nearly impossible to avoid crashing. Why do I need to add a RF shield in the first place? Did someone at ModalAI test this $5,000 drone before shipping it to me? Does the Starling 2 Max have a GPS design issue? In view of the two similar reports below I'm beginning to think so. Please let me know how we can make this right.

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

@Alex-Kushleyev Actually I discovered something very interesting. No matter how long you leave the drone outside it will not lock onto any satellites, BUT if you add an aluminum foil shield between the GPS antenna and the rest of the drone you immediately get satellites, a total of 11 after a few minutes. See pics below.

I think this means I need an RF shield of some sort. Open to suggestions.

Note that this is with the Lepton cable disconnected, and the ALFA wifi module removed. I'm communicating using ssh via 5G Google Fi and Tailscale as per ModalAI documentation, which was super helpful, thanks!

Thanks again for helping me figure this out!

@Alex-Kushleyev OK, I made a cable and connectors and the GPS receiver appears to work fine when connected to my PC USB serial port and the whole drone is powered off, details below. Definitely a major step forward. What do you think I should test next? I'm thinking of testing the pin-to-pin continuity of the GPS-to-VOXL cable, and also checking that the wires are connected to the correct pins. Any other suggestions?

Thanks for your help!