Gps loss once windows starts

gtd86 · 01-14-2004, 05:05 AM

Hi,all

I have a usb gps device from ebay

http://cgi.ebay.co.uk/ws/eBayISAPI.d...&category=4668

(one of those)

And i have plugged it in and installed the usb to serial driver, and sometimes works ok after installation, but when the pc is turned off the gps finds a fix no problem but as soon as windows boots up it loses the fix, and if i try and run the software it tracks some satellites but can't get a gd signal from any of them and just searchs?

I am using the wee test app that came with it, and autoroute which i tried and worked couple of times.

Really need help with this

Thanks

wi77iam · 01-14-2004, 07:23 AM

Quote: Originally Posted by gtd86

And i have plugged it in and installed the usb to serial driver, and sometimes works ok after installation, but when the pc is turned off the gps finds a fix no problem but as soon as windows boots up it loses the fix, and if i try and run the software it tracks some satellites but can't get a gd signal from any of them and just searchs?

How do you know the gps "finds a fix" with the PC off? The usb-serial driver won't work without the PC running. The gps is just a signal receiver - the software on your PC reads the NMEA data stream and computes the fix. If you can get it to work sometimes (with the PC on), then your problem is most likely poor reception - you need a good clear view of the sky.

sxpert · 01-14-2004, 09:00 AM

Quote:

he gps is just a signal receiver - the software on your PC reads the NMEA data stream and computes the fix

bzzzt... wrong, thank you for playing...
the GPS receiver does all the calculation and gives via NMEA all the cooked data. the PC only has to display where you are on a map.
now, I suspect the GPS receiver, as it is USB powered, needs the PC to be on to be powered (and thus be able to receive something). so you really need the PC to be on when you need to get gps data.

wi77iam · 01-14-2004, 01:17 PM

I think I said that the gps outputs the NMEA data. But there's a lot more that the PC has to do to take that output and compute a fix, which is a meaningful representation of your position. Things like converting the usb data stream to serial data, then taking the serial data from the comm port and converting to ascii data, then using the latitude/longitude numbers and translating them to x-y coordinates that can be plotted on a map. The PC doesn't just magically "display it on a map". There's a little "cooking" going on in the PC, too.

My point is that the gps mouse cannot work without the PC, both for power and for processing the gps output to a usable form.

Laidback · 01-14-2004, 01:24 PM

Quote: Originally Posted by sxpert

bzzzt... wrong, thank you for playing...

And life got a little bit tougher!

Confused · 01-14-2004, 02:29 PM

Guys, you're getting mixed up!

If you look at the listing, it says it has an LED, which functions as follows:
LED OFF: Receiver switch off
LED ON : No fixed, Signal searching
LED Flashing: Position Fixed

So I guess gtd86 is looking at the LED, seeing it's flashing, which means it has a fix, then going solid when windows boots, saying it's looking.

Not that I know the answer, but thought i'd clear that up

Confused

NJay · 01-14-2004, 02:35 PM

Wi77lam,
I think whats getting people is that you keep saying the PC is computing the fix when its not, as that's already done by the GPS device (assuming it can lock onto enough satellites) and is present in the NMEA data sent back.

If you'ed just said the PC translates this long/lat fix into a position on a map then Sxpert would be happier

GTD86, most USB GPS deivces have a little led on them that flashes when its searching and goes solid when the GPS device has got a fix. Can you explain at what point you believe the GPS device has got a fix as like others on here have said it can't get a fix if you haven't got the machine turned on. Unless......

.....don't suppose you have it plugged into a powered usb hub do you???

In which case what might be happening is that its getting a lock just sitting there with the pc off as it only needs power to do this not a connection to the PC. Then when you load up your PC and windows, something (either the Test GPS program or Autoroute) is doing a reset on the GPS device which will cause it to reacquire its fix. Since this needs more satellite info (as it needs a complete message from at least 3 satellites), then when its got the fix (can keep the lock with only partial messages from each satellite) it will appear as though windows has caused the fix to be lost.

Does this make sense - probably not

Laidback · 01-14-2004, 02:39 PM

Quote: Originally Posted by Confused

Guys, you're getting mixed up!

If you look at the listing, it says it has an LED, which functions as follows:
LED OFF: Receiver switch off
LED ON : No fixed, Signal searching
LED Flashing: Position Fixed

So I guess gtd86 is looking at the LED, seeing it's flashing, which means it has a fix, then going solid when windows boots, saying it's looking.

Not that I know the answer, but thought i'd clear that up

Confused

I saw that.....Hmmm, now if I had made it I would have had flashing = searching & On = Fixed. Seems more logical that way...

Confused · 01-14-2004, 02:43 PM

Quote: Originally Posted by Laidback

I saw that.....Hmmm, now if I had made it I would have had flashing = searching & On = Fixed. Seems more logical that way...

Yeah...that's what I thought was more logical...maybe the listing was wrong about that :confused;

Garry

Laidback · 01-14-2004, 02:50 PM

Gtd86, what info do you get from the test app? Maybe try VisualGPSXP as this gives quite a bit of info such as signal strength etc.

NJay · 01-14-2004, 02:55 PM

Hmm, you maybe right but that's the opposite way around to the Haicom USB GPS devices as they are:

LED OFF: No Power
LED Flashing: No fix, searching
LED Solid: Fixed

Anyone know what actual model that is rather than just the chipset type

NJay · 01-14-2004, 02:59 PM

Nevermind found it

http://www.globalsat.com.tw/english/...n_id=5&p_id=12

So yep looks like its the opposite way around then, Doh!

unsavory · 01-14-2004, 04:31 PM

No, mind is:

LED OFF: Receiver switch off
LED ON : No fixed, Signal searching
LED Flashing: Position Fixed

So probably depends on the GPS Receiver manufacturer.

Mine is a Holux GM-210

NJay · 01-14-2004, 06:25 PM

unsavory,
Yes that exactly what I meant.

Its seems to vary between manufacturers and hence the doh was coz I was can't believe I didn't realise this earlier

wi77iam · 01-14-2004, 07:22 PM

OK I guess I'm the stupid one. Yes, the little LED means the gps has acquired enough sats to compute the fix. Sorry. Seeing the word "fix" took me back to my days as a Naval Aviator and I confused it with a position displayed on a map (actually we used charts).

I can see now how he had a "fix" even with the PC off, assuming he used a powered usb hub.