I have measured Beaglebone Black radiated energy around the 1575 MHz band that GPS uses with an SDR spectrum analyzer using GPRS on a MacBook Pro. It does not seem to be harmonically related to the BBB Clock. It is possibly related to the HDMI video circuit... Spectrum with BBB ON:
<https://lh6.googleusercontent.com/-3UzV31XcvwM/U7obp6C432I/AAAAAAAAGn8/75NV0_4m3xY/s1600/Spectrum_BBB_On_GPS.jpg> Spectrum with BBB Off: <https://lh6.googleusercontent.com/-P9o5Wic5lpQ/U7ob62YIRVI/AAAAAAAAGoE/a3dg1JSmZyQ/s1600/Spectrum_BBB_Off_GPS.jpg> On Sunday, November 17, 2013 5:55:46 PM UTC-6, juanc...@gmail.com wrote: > > Hello everyone, > > Sorry for the reposted message. I had posted this on the BeagleBone group, > but this is an issue with the BeagleBone Black. > > 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! > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
