This weekend I reinstalled my ADSB receiver after not touching it for 3 years. I installed Bookworm on my PI4 and built PiAware as instructed from source. I have an Airspy R2 plugged into the blue USB3.0 port and a USB GPS puck in the USB2.0 port. Everything is running well. Yesterday I installed RaspiBackup with the idea to make regular backups on a USB memory stick.
A couple of minutes after sticking the USB memory stick in the USB 2.0 port of the RPI, MLAT was faulty and reporting “unstable time”. I also noticed that the GPS time was off by 3-4 seconds. After some troubleshooting, removing the USB memory stick, and resetting, MLAT was up and running again. Moving the USB memory stick to the USB3.0 port, does not solve the issue.
Either it is the RPI4 USB, Bookworm, or the USB stick itself causing this. This evening I will continue troubleshooting with a different USB stick.
Does anyone ever see the same/similar problem (and has a solution)?
Don’t know what your specific solution is but will say that my experience shows that mismatches of USB 3.0 and 2.0 ports and devices will not normally go well and cause mismatched USB devices to drop out and not play well with others.
I tested with a couple of other USB sticks and the problem remains. MLAT stalls and the error is “Local clock source is unstable”. I have one other PI running 24x7 and I will use this one as “backup server”.
FYI. Your location latitude and longitude have to be extremely accurate and not just close. MLAT relies on and demands very accurate location data. Anything it senses as inaccurate is labeled as unstable and they shut you down. Went through that very issue during initial setup of my site.
RPI4s and below share a single USB bus when a 2.0 device is plugged in. The airspy(I have several) uses a lot of USB bandwidth. When it has to share with other USB devices MLAT becomes unreliable.Try using just the airspy only. Leave it for an hour or so, then add the other devices, one at a time.
Odroids(I have several) and the new RPI5 have better USB setups.
Curious why you are using a USB GPS puck instead of hard coding your system location as an input to the Flightaware system? Maybe there is more to the USB GPS function that you are using for other purposes. If it exists for just locating your system, I suggest it’s just a waste of compute USB resources.
An unstable clock is related to power. The RPi most likely can’t send enough power to the USB ports. Try removing the GPS puck to see if the problem is gone. In that case the best solution is using an externally powered USB hub.
You are right. I also use it as time source but can also use NTP from my network. I will run a test by unplugging the GPS puck and see if this makes any difference.
I tested removing the GPS puck but it did not make a difference. I was able to buy an RPI5 and this seems to solve my problem. Everything is plugged in directly to the UBS ports (Airspy R2, GPS, USB stick) and everything is running fine.
The USB ports are so closely spaced, how you managed to plugin all that stuff directly? For me it is not possible to plugin even two dongles (1090 & 978) directly and I have to use a short USB extender cable for one of the dongle.
The airspy R2 and GPS puck are connected with usb cables anyway. The USB stick I use is a Samsung FIT Plus 256 gB and is of similar size as a USB plug. .
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