From: Hugo V. <hug...@gm...> - 2006-05-04 03:34:24
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I used a u-blox GPS with a PXA255 (not a Gumstix, but very similar system) last year and had the same problem (or at least the same symptoms). I noticed that the XScale PLL has a harmonic almost exactly on the GPS frequency when it is set up to run at 400 MHz. I found underclocking the XScale to 300 MHz completely solved the problem. Admittedly, my GPS was not amazingly well isolated from the XScale (separate board, ground planes connected via a ferrite). I changed the CPU frequency in U-Boot, but changing it using the cpufreq system should work fine too. Also, u-blox has a rather nice (albeit Windows only) application you can download that displays an abundance of information about the status of the receiver; you just need to attach your receiver module to a PC via a RS232-type circuit. Cheers, Hugo Vincent > Date: Wed, 03 May 2006 20:51:15 -0500 > From: John Cole <co...@lg...> > To: gum...@li... > Subject: Re: [Gumstix-users] Gps on gpstix > Reply-To: gum...@li... > > I connected my spark fun antenna with a very clear look at the sky this > evening for over 4 hours without ever receiving a fix. I am wondering > if I don't need to send some kind of initialization string to the gps. > I have used many different models of garmin gps with gumstix before and > never had a problem finding satellites, so I am confused also. > > John > > Jon Keller wrote: > > > Is that to say that if a backup battery is not supplied and we're on > > the opposite side of the planet, that it will take a considerable > > amount of time to get a fix, each time we use the gpsstix? And I know > > it probably depends a lot on where we are, but how long should a > > considerable amount of time be? > > > > I'm yet to get a fix with my gpsstix however the antenna I'm using is > > rather old, and I haven't received my one from sparkfun yet. I'll wait > > for that one before I think that it's really not working. > > > > > > -Jon > > |