TomTom Wired GPS Vs Leadtek 9532

[RichDem]

I have just finished setting up a friends pocket pc based GPS system, it consists of an Ipaq 4150, 256mb SD card, TomTom navigator 2.24 & GPS 2.09 & a TomTom wired gps receiver.

I have a very similar setup apart fom a 3950 & Leadtek 9532 with gps 2.06. I set the new system exactly as mine and that is using the SIRF 4800 driver. Everything is fine getting a 3d lock but when you drive the position shown on the map in "Navigator" display is a good 10 - 12 seconds behind your actual position, i.e you pull up next to a side road and you can sit and watch your position on the map carry on to your exact position, this normally takes around 10 seconds.

I know it is not his setup as I tried my Ipaq connected to his receiver and it did the same. I changed the driver on both IPaq's to the default TomTom gps driver or NMEA 4800 and the problem corrects itself and the position on the map is correct to your actual position in the road.

Does the default TomTom driver run in NMEA or SIRF? I had loads of problems at first with the signal dropping out when using NMEA but since I have been running in SIRF my receiver has performed flawlessly.

I was under the impression that the TomTom receiver is a re badged 9532, but there is definately a problem when you use the SIRF 4800 drivers.

I was wondering if anyone can throw any light on this rather strange problem.

Best Regards

Richard
_________________
If it ain't broke then fiddle with it until it is!

[lbendlin]

Yes, we have seen some cases when switching to SiRF protocol has produced this lag.

Don't forget that SiRF protocol and SiRF chipset is no the same thing. Generally you should run your serial receivers at NMEA 4800 - that's because all receivers support that by default, and because there's absolutely no advantage to use the SiRF binary protocol. (if you put aside the academic considerations of serial buffer and cpu wait cycles etc)

So even though both devices have the SiRF chipset (which is a good thing because of their sensitivity) they both are talking NMEA natively.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

[RichDem]

Hi Lutz,

As I said in my post I used to run my 9532 in NMEA simply because the TomTom drivers back then did not support SIRF. I must say since I have been able to use SIRF as a driver the whole thing has been superb. I travel alot to London and allways used to struggle when travelling down streets with high sided buildings. I even had times when during a morning trip of say 1 hour the signal would keep dropping off the whole time. But now this never happens.

The strange thing is that my receiver runs absolutley fine in SIRF and my friends doesn't. As I mentioned aren't the TomTom receiver and my 9532 one and the same thing?? I have never seen this problem before with my current setup.

Richard
_________________
If it ain't broke then fiddle with it until it is!

[lbendlin]

Again, the protocol that you use has nothing at all to do with the sensitivity of the chip.

The tricky part is that some of the protocol implementation in the firmware can actually detrimentally affect performance. And this is where your problem will be - the two receivers will most probably run different versions of the chip firmware.
_________________
Lutz

Report Map Errors here:
TomTom/TeleAtlas NAVTEQ

[Dave]

As Lutz says, switching between NMEA and SiRF won't adjust sensitivity, the only thing it will do is if you lose a signal you will find it re-acquire quicker in SiRF mode, but equally you can see it drop the signal a lot quicker.

[RichDem]

As ever, thanks for your help guys, I was more curious as to why basically there was a difference between two identical receivers (maybe they are not exactly the same, firmware etc) My friends TomTom receiver seems to be working OK, I must admit I haven't tried NMEA for some time, maybe it is better with the latest drivers.

Regards

Richard
_________________
If it ain't broke then fiddle with it until it is!

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