GPS takes forever to lock

andro · 08-30-2006, 04:15 AM

Hi guys&gals,

I'm using a Sirf3 based USB GPS receiver (in NMEA mode). When I park my car in the garage overnight, the next morning the GPS takes forever to lock. After an hour or two, when it eventually locks, I always have 6-10 satellites locked so the visibility of satellites from the GPS should not be an issue. I think there is a misconfiguration of the GPS that's to be blamed for this, but I don't know what I should do to fix this. What can I do, anybody got a clue?

The GPS is a Haicom HI-204III USB. It is constantly powered from USB (i.e. also overnight). I'm pretty sure my car doesn't do a couple of hundred miles before the satellites are visible again

and the manufacturer also claims <40sec from cold start till lock

sama · 08-30-2006, 04:45 AM

perhaps you have a difference between teh baud rates?

check in your device manager that the comport for the GPS matches the specification of the receiver. Mine is a different brand SIRF III, and that runs at 4800.

you also need to make sure your software (iGuidance in my case) also has those settings.

let me know if that works

andro · 08-30-2006, 08:44 AM

As I said, I have no problem after an hour or two in any software. Just after I come out of the garage there is no satellites locked, or maybe one, then after a *lot* of time two, and so on. If there would be a problem with baud rates, it wouldn't ever work.

I'm using 9600bps for the GPS (which works without a glitch after a couple of hours), I'm using GPSGate (to be able to use multiple apps with it) and GPSProxyPC (for Garmin) and a couple of other NMEA apps (Destinator and a local mapping software with the best maps).

DarquePervert · 08-30-2006, 08:48 AM

The GPS should be 4800 bps, not 9600.
That could very well be the issue.

sama · 08-30-2006, 08:55 AM

failing that, you could try the gps on a home computer say, with it dangling out the window, and see if you get the same behaviour.

the way I see it, it's either a hardware fault, or a config issue.

andro · 08-30-2006, 09:08 AM

Look, guys, you don't listen (or, well, read

) what I write. If this was a baudrate misconfig, I would *never* get a lock of *any* satellites. The GPS doesn't just go flipping from one baudrate to the other after a couple of hours.
I drive away from home in the morning. I don't have a lock to enough satellites when I drive (and it is normally 0-2 satellites, if it was a baudrate misconfig, it would *always* be 0 satellites and I wouldn't be getting normal NMEA data from the GPS when I check it - just without locked satellites, of course). I park my car in front of the office (clear view to the sky), come back a couple of hours later, instantly, like, 8 satellites locked. Sure - the GPS was powered and trying to lock all the time, and it eventually did.

What I need is the way to persuade the GPS not to lose information and resume from where it left off when I went into the garage. Or, whatever, do a cold boot and start up in under a minute

DarquePervert · 08-30-2006, 09:34 AM

No, that's not true.
The PC is trying to talk to the GPS at one baud rate, but the GPS is sending at another. I'm not saying this is definitely the source of your problem, but it's certainly a likely candidate.

Besides, this is such a simple thing to try and it doesn't cost you anything but a couple minutes of time to investigate. Is it worth spending a few minutes to try something that might alleviate your problem? Even if it doesn't fix it, you're not out any money and nothing is permanently altered.

If you don't want to try our suggestions, then good luck to you.

andro · 08-30-2006, 09:44 AM

Quote: Originally Posted by DarquePervert

No, that's not true.
The PC is trying to talk to the GPS at one baud rate, but the GPS is sending at another. I'm not saying this is definitely the source of your problem, but it's certainly a likely candidate.

The GPS is configured for 9600 (the navigation software agrees, SirfDemo agrees). I will emphasize again: if baudrate misconfig would be the case, why would the GPS just lock after a couple of hours? There is no way the baudrate is changed in the software in the meantime.

Quote:

Besides, this is such a simple thing to try and it doesn't cost you anything but a couple minutes of time to investigate. Is it worth spending a few minutes to try something that might alleviate your problem? Even if it doesn't fix it, you're not out any money and nothing is permanently altered.

If you don't want to try our suggestions, then good luck to you.

I have tried plenty of things, including altering the GPS config from 9600 to 4800, to 57600 (like it is when in Sirf mode), and there is no difference in how fast it locks. I have quite some knowledge on communication protocols and such, so I know from experience and from trying, that the baudrate is correct (I get jibberish when I set the comm to 4800 and I get NMEA data when I set the comm to 9600 - so the 9600 rate must be correct, am I right?).

What I am worried about is that I have screwed up something when I was switching between SIRF and NMEA protocols using SirfDemo. This is the area I need some help...

And please, don't get me wrong, I am very open to suggestions, I certainly don't want to be a smartass and am very greatful for suggestions, but I am 100% certain that baudrate is not the problem here.

sama · 08-30-2006, 09:50 AM

now you listen here...

we're only trying to help you. so like Darque said, tryng it doesnt' harm. your theory of it not being the cause is as strong as our theory that it is.

think of it this way... you have two flasher indicators workign at different speeds. at some point, they alias and conincide after a while

now 4800 is half of 9600, so it well be that, since after a while, when the sreams are alligned, every two samples picks up at least one. let me ask you this, have you tried it for 6 hours? does it stop after six hours?

now go and bloody try it, before I lump you one in the head!!

if this doesn't work, then try it on another pc. if it's the same, then you probabvly have some faulty h/w that doesn't remmeber. perhaps the memory that keeps track of satelites is buggered.

sama · 08-30-2006, 09:52 AM

perahps switching protocols did it, why don't you switch it back and try again?

andro · 08-30-2006, 10:15 AM

Like I said, I tried it already, that's why I know this is not the problem

Once I get the lock, it doesn't go away until I go into the garage again. And this is usually after 12-14 hours. I'm pretty sure if I leave the car outside (but, this I won't do if I don't have to

), in the morning the lock will be just fine. Hm, maybe I can try connecting it to my notebook in the morning instead of leaving it on the CarPC and see if there's any difference.
I have also tried switching protocols around again to SiRF and back to NMEA. It'd be interresting to see whether the same thing happens when in SiRF mode, maybe I'll try to do that too. Unfortunatelly, the Destinator implementation now in Centrafuse, which I'm using, has some problems now with connecting to GPS if it's connected directly to it (that's also why I'm using GpsGate as an interface), so I can't try SiRF mode with navigation (I'll try it though with SiRFDemo). But, please don't hump on this Centrafuse info thingy, I'm looking at GPS information with GPSInfo or SiRFDemo.

MatrixPC · 08-30-2006, 10:46 AM

Try this, instead of driving right away, just pull the car out of the garage and wait for a minute or so. You get better/faster lock when the cord doesn't change.
I do have that problem sometime especially when it's overcast. After pull out the garage and drive right away, it won't get a lock until I stop at the light. So instead of drive after pull out, I stop on the drive way and pick up the paper. When I return, it get lock.

xBrady · 08-30-2006, 11:03 AM

Sounds to me like it is a hardware problem. The only software settings that your applications can change are the settings associated with reading from the port. All your software does is get the data from the port and parse it. Your applications have no effect on how quickly your receiver gets a lock. If the baud rate is set so that your applications can read the NMEA data then it has nothing to do with your com port settings.

Wiredwrx · 08-30-2006, 01:57 PM

Quote: Originally Posted by andro

Hi guys&gals,

I'm using a Sirf3 based USB GPS receiver (in NMEA mode). When I park my car in the garage overnight, the next morning the GPS takes forever to lock. After an hour or two, when it eventually locks, I always have 6-10 satellites locked so the visibility of satellites from the GPS should not be an issue. I think there is a misconfiguration of the GPS that's to be blamed for this, but I don't know what I should do to fix this. What can I do, anybody got a clue?

The GPS is a Haicom HI-204III USB. It is constantly powered from USB (i.e. also overnight). I'm pretty sure my car doesn't do a couple of hundred miles before the satellites are visible again

and the manufacturer also claims <40sec from cold start till lock

Is it USB? Are you using Hibernate/Standby or Shutting down. Could this be a resume from Hibernation/USB issue? Have you tried pulling and reinserting the GPS? What happens?

Michael

vr6exy · 08-30-2006, 03:14 PM

im having the resume from hib prob. gps will not connect unless i pull and re-insert usb adaptor