Beaglebone Black, GPS, and RF interference

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1

Hello everyone,

Sorry for the repost. i had posted this on the BeaglBone group, but this is a BBB issue.

I am having some problems trying to use a GPS receiver with the BeagleBone black. I connected a PMB-648/688 module to one of the BBB UART ports. I can see the NMEA messages coming from the GPS receiver, but I never get a valid fix. I doesn’t report any satellites in view (GPGSV messages). Not even if I leave it on my rooftop for a couple hours.

Initially I thought it might be a problem with the GPS receivers, so I tested them on my laptop. Every one of the receivers I have worked fine, taking a less than a minute to get a fix from my window.

The next thing i thought was that there might be some power supply noise messing with the GPS receiver, so I tried powering the receiver by itself (connecting the grounds of my receiver supply and the BBB). Surprisingly, this worked. More surprisingly, it stopped working If I moved the BBB close to the GPS receiver.

This lead me to suspect that the BBB might be causing some RF interference on the GPS frequency band. My next test was to have the GPS receiver and the BBB powered independently. This confirmed my suspicion. If I powered the GPS receiver, waited until it got a valid GPS fix, powered the BBB, and placed the BBB close to the GPS receiver, the I would get the same result as before. No GPS fix, no satellites in view. Since the two devices are being powered with two independent power sources, then the BBB must be causing some RF interference. I do not have a RF spectrum analyzer to confirm this, but I do not see any other reason.I tested this with three different BBB and 6 different PMB-648/688. I always got the same result.

I tried the same GPS receiver on a Raspberry Pi and It works fine, so that is what I am going to work with for the moment. But I really like the BBB, and would love to use it for my application. Is there anything I could do to fix this?

I’m sure other people have used GPS receivers with the BBB. Can anyone recommend a GPS receiver that works with the BBB? I’m looking for a receiver that’s approximately the same size (3cm*3cm) and price ($35-$40) as the PMB-648/688. I’m getting the Adafruit Ultimate GPS soon, so I’ll report about that.

Thanks!

–Juan Camilo

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Hi Juan,

Interesting problem. I’m using a Ublox UP501 GPS module with my BBB and haven’t experienced anything like that. I can also run the module right next to the black without issues. However, I have a large cape that covers the BBB and my power source is a battery with a heavily decoupled supply feeding the BBB and the GPS. The GPS module also has its own regulator and filtering. Here’s a picture of my setup if you’re interested.

Pretty sure that the UP501 uses the same MediaTek chipset as the module that Adafruit carries. It’ll be interesting to hear what your results are with it.

-Ron

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I never had problems with GPS receivers I used with Beagebone White, even when the antenna was inside a building, far from a window. I did however had very big problems with the same receivers connected to mbed, with antenna having open sky above, so I don’t think that Beaglebone should cause any problems with reception.

j.

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I have the same problem with my BBB and an Adafruit GPS. I made a U shaped copper shield and put it under the board. If I connect the BBB common to the shield the GPS works great. When I remove the shield ground it get’s weaker but is still better than with out the copper shield. I also tried a cast aluminum box without a lid and that fixed the problem but it’s too big for my application.

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I had the same issue with my Adafruit GPS. I was able to resolve it by shutting off HDMI.

Keith

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I have the Adafruit Ultimate GPS (https://www.adafruit.com/product/746) on a BBB right now, and I get a fix often inside, I have yet to try outdoors. Though that is quite interesting that your having RF issues! How did you shutoff the HDMI, super beginner here with respect to embedded devices.

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Hi Theodore,

Add the following to uEnv.txt kernel options
capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN



This was valid for the kernel I was running.



Keith
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That temporarily bricks my BBB. That exact line ts in the uEnv.txt file in the distro I use, it is just commented out, so I uncommitted, rebooted and all LEDs are on, cant connect to the board. Have to re-flash to get a connection again. Odd!

I’m running Debian 7.9 (wheezy)

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I’m using Android with a 3.8 kernel.

Keith