GPS module reliability

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GPS module reliability

Unread postby benwillcox » Fri Sep 01, 2017 5:07 pm

Hi all,

I am interested to know if other users have any issue with reliability of the Odroid GPS module? I ask because I believe I know of 3 or 4 units that had suffered issues.

The first module was my own that worked ok for around 10 months, then started becoming intermittent and then eventually failed completely, drawing a lot of current from the USB port. My replacement module (under warranty) has been working ok for a few more months, but now appears to have become intermittent. If I ssh into the Odroid when it's not working, when I 'cat /dev/ttyACM0' then I receive no data. If I unplug and replug then the device usually works again.

I have now heard of another user with the same intermittent problem, and I have just last week installed a new system for another user, and his GPS is also intermittent after only a day or so - sometimes it works again after a hard reboot, sometimes not.

We are all running the very latest 6.0.1 build. Does anyone have similar issues?

Thanks,
Ben
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Re: GPS module reliability

Unread postby benwillcox » Sun Sep 03, 2017 11:13 pm

Hello again,
I've done more testing and it seems that this could be a compatibility issue with the Bluetooth CSR4.0 module and the GPS module. I am running the latest 6.0.1 Android build.

Here's what I have established:
- Boot Odroid with Bluetooth and GPS connected. Cannot receive any data from /dev/ttyGPS.
- Unplug bluetooth module, and re-plug the GPS. Now I get the data stream from /dev/ttyGPS.

OR if I just boot the Odroid without the bluetooth plugged in then the GPS works no problem.

lsusb shows the Bluetooth device as 0a12:0001.

Can anyone replicate this issue?

Thanks,
Ben
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Re: GPS module reliability

Unread postby benwillcox » Tue Sep 12, 2017 9:03 pm

Hi all,
I have done some more research, and now know of several users that are having the same problems. However, my latest test results have not yet identified where the problem is. If I can expand on my previous post where I thought the Bluetooth module was causing a problem, it now does appear that it's not specifically the bluetooth module, but either 1 or more 'other device' connected to the USB of the C2, including my wifi, bluetooth, or Arduino Leonardo.

It appears that with no other USB device in the C2 except the GPS, that it works fine. Then most of the time with another device connected, the GPS will not work at all, or sometimes work for a few seconds then the NMEA stream from /dev/ttyGPS will suddenly stop.
The strange this is that this has worked without problems for many weeks, and seems to have started to become a problem recently. I have considered several possibilities:

- Compatability problem with other USB devices e.g. Bluetooth, wifi etc
- Problem with USB hub
- Voltage drop/stability under load, e.g. PSU or cabling problem
- Noise on power supply
- GPS module failure
- GPS module location picking up noise/interference
- Software issue with the Android version
- An installed App causing a conflct

I have been working through these to eliminate the possibilities:
- Removed USB hub and have devices plugged directly into the Odroid.
- Powered the GPS device from a separate stable 5.00v PSU
- Moved the GPS module to another physical position
- Rolled back to 6.0.1 release v3.0 (prior to the GPS module ACM number allocation fix)

None of these seems to have changed the situation. The GPS module works fine in U-Center on a laptop.
I also had another brand new Odroid C2 and GPS with the same hardware configuration (but fewer Apps installed) which did not exhibit any problem.

My most recent tests have been to change the CPU Frequency in Odroid Utility down to 1.5Ghz (was 1.7Ghz), which has appeared to make this much more stable. However I tested rebooting again this morning after leaving the system running all night, and now each time I boot the GPS stops straight away.

I'm running out of ideas now, but I've ordered another C2 and GPS module to try new hardware with a fresh software installation. The easy answer would be that it's a faulty GPS device, however I find it hard to believe that the same issue is affecting several users, and the module appears to be fine in U-center on another computer.

Ben
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Re: GPS module reliability

Unread postby odroid » Wed Sep 13, 2017 8:31 am

Thank you for the very intensive research and tests.
I saw some people reported a random USB malfunction issue when low-speed(USB 1.0) devices and high-speed(USB 2.0) devices are connected together.
But our USB-GPS is full-speed(USB1.1) device and there should be no critical issue probably.

I have one idea worth to try.
If you have an OTG-to-Host cable something like this, please connect your GPS receiver to the C2 OTG port.
http://www.hardkernel.com/main/products ... 0193470720
If the GPS doesn't work, place a USB hub between the otg cable and the GPS receiver.
This configuration can assign a separated root USB host in the SoC to the GPS only.
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Re: GPS module reliability

Unread postby benwillcox » Wed Sep 13, 2017 5:37 pm

Thanks for your reply Odroid.

Your suggestion sounds likely - in fact last night I tested with my mouse, keyboard and Arduino all connected via a small passive hub into the OTG port, leaving my Wifi/Bluetooth/GPS in the normal USB ports on the Odroid, and this seems to have fixed the problem.
I will also try your suggestion to isolate the GPS on the OTG port, although I thought I read somewhere that the GPS is not supported on the OTG port which is why I haven't tried this already. (EDIT: I read it here: http://www.hardkernel.com/main/products ... 2502154078 is it true?)

I will update the thread with my results, many thanks for your help.

Ben
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