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09-12-2006, 11:49 AM
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#1
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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Connexant TU40 D140 GPS receiver module
This module is on Ebay for $15 buy-it-now.
I  this forum with "TU40" "D140" and nothing shows up.
Is this any good? Can I use this with the "shark fin" type roof antenna that you can buy from MP3CAR store?
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09-12-2006, 12:17 PM
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#2
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,911
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Well, considering I can't find it on either EBay or Google, I have no idea. I also put in the correct spelling of Conexant.
Perhaps a link to your EBay auction might help us glean more information about the module you're looking at.
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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09-12-2006, 12:58 PM
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#3
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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Too bad I can't change the thread title.. My bad.
Well, I downloaded a "white paper" of this board. I don't know much of anything but the paper was written in 1998. So it'd be safe to assume that this thing was made before then.
Has there been a leap of technology in GPS since 1998? If it works just like the ones I can buy today, then I'd buy one...
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09-12-2006, 01:38 PM
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#4
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,911
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Again, I'll ask...
Do you have a link to the Ebay auction? If someone could actually see more than just a chipset description, we might be able to give you more information.
If you're not willing to give that up, then best of luck to you.
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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09-12-2006, 03:56 PM
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#5
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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09-12-2006, 04:33 PM
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#6
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,911
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OK. Now we're getting somewhere.
That appears to be an OEM GPS receiver unit.
You'd need two things to get this working on your PC:
1) An antenna. In regards to your question about the Hirschmann unit in teh mp3car.com store, it should work with this module, but you might need an adapter for the antenna. Thsoe are readily available, though.
2) You would need to get the device to output to a serial port. The datasheet says it has a serial interface, but the photos don't show any connector. It's likely that the two rows of pins on one side of the board are for that purpose, but I'm not 100% certain.
OK. After looking at the white paper, the two parallel rows of pins are for the serial connector. The white paper has pictures of the same unit (albeit a different revision) with a pin connector in that location.
Will this work? Probably. You'd need to supply +5v power (available via a serial port) and have a serial connection. You're probably going to be doing some soldering, too.
But for an OEM GPS receiver, that's not a bad deal, IMHO.
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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09-12-2006, 10:11 PM
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#7
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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Like you said, the Pin J1 - 11,12,15 and the power line are probably all the RS232 needs. Solder some header pins to connect to DB9 connector, and it should be usable.
But.. I noticed something weird.
Looking at the page 5 of the white paper, the Table 2. GPS receiver Navigational Accuracies.
The accuracy is in the order of 50 meters! can this be right? I hope it's some kind of typo. May be they didn't put decimal place in front of 50... If it is 0.50 meters, then it would make perfect sense. But 50 meters... hmm.
Also on the Page 4, Table 1, Time To First Fix.. the cold TTFF is 2 minutes. does this seem right? May be I should connect a small solar panel+NiMH battery and keep it "alive" all the time...
All and all, with all these USB devices and peripherials, looks like I'll be quickly loading up my 5V from the PSU.. better patch in a POL PSU..
Last edited by jasonsjwou; 09-12-2006 at 10:15 PM.
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09-12-2006, 10:14 PM
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#8
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Neither darque nor pervert
Join Date: Apr 2004
Location: Elsewhere
Posts: 12,911
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I'd think the 50m accuracy would be the distance from the receiver to the satellite, not the accuracy of your positioning. 50m over a distance of a hundred miles is pretty miniscule, and wouldn't amount to very much when your position is triangulated.
Any other GPS gurus want to chime in here? I could very well be wrong on this...
__________________
LOOKING FOR THE FAQ? IT'S HERE.
You never found that link, did you? Why? It's hard to find in the NavBar across the top of the forums, amongst a lot of other crap.
TELL MP3CAR YOU WANT A LINK TO THE FAQ IN A MORE OBVIOUS, NOTICABLE LOCATION HERE.
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09-12-2006, 10:36 PM
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#9
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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I'd certainly hope 50m would be the receiver-satellite accuracy... If the actual positioning accuracy is 50 meters, then this is completely worthless.
Also, what benefit would I get if I add a "Preamplifier" mentioned in the white paper? will the reception under bad weather improve? I wonder what the requirements of the Preamp is..
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09-13-2006, 02:29 AM
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#10
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Newbie
Join Date: Oct 2005
Location: Mumbai, India
Posts: 50
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50 meters would be the positioning accuracy. i read somewhere civilian gps has an accuracy of 30 mts.
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09-13-2006, 03:04 AM
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#11
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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NO WAY!!!! 50 meters would be something like 1 block. If the accuracy is 50 meters, the how do we get street level GPS navigation?
Is it because this receiver module is old?
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09-13-2006, 03:31 AM
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#12
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Newbie
Join Date: Oct 2005
Location: Mumbai, India
Posts: 50
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i guess 50 mts would be at its worst, with just 1 satellite fix
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09-13-2006, 07:23 AM
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#13
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Maximum Bitrate
Join Date: Jun 2003
Location: Hatfield, PA
Posts: 580
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50 meter accuracy for 15 bucks - that sounds about right. This is probably using an old gps chipset, which reads fewer channels, which means less accuracy. I didn't read the white paper - How many channels and what is the sensitivity? Those will determine how many satellites can be picked up.
As a comparison, look here at the current chipsets available. The newest Sirf III chipset has 20 channel capability and can do 10m accuracy or 5m with WAAS.
If you want accuracy, spend a little more.
__________________
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09-13-2006, 11:32 AM
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#14
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Low Bitrate
Join Date: Sep 2006
Location: KOREA,USA,AUSTRALIA
Posts: 104
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It says 12 satellite tracking channel.
RF Input 1575.42Mhz (L1 band) at level between -130dbBW and -163dBW
Looking at the spec sheet of the newer GPS receiver,
http://www.sparkfun.com/commerce/pro...roducts_id=465
they are tons better... Especially TTFF... under 45sec. That's fast.. this has 2 minutes.
I guess it'd be better to put this module inside the "Fake" shark fin antenna housing and mount it on the roof, and connect it to PC via RS232 cable. I'll have to remove headliner and drill a hold to do this, but that'll be THE perfect solution...
Thanks a bunch.
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09-13-2006, 12:50 PM
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#15
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Maximum Bitrate
Join Date: Jun 2003
Location: Hatfield, PA
Posts: 580
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The ebay auction doesn't mention an antenna. You will need an antenna to go with this module - I hope you realize that. A good one will cost as much as the module, or maybe more. Oh and you will also need a voltage regulator since the module takes 3.3v and you'll probably want to power this from your car's 12v.
I don't think you want to run power and rs232 to your roof. You should just mount the module on your mobo or in your PC case, connect to a comm port, grab power from your PC, and then just run thin coax to the antenna mounted in the fin on the roof.
Just so you know, you can buy a 20 channel SiRF III based eval kit at Sparkfun, which includes the module, magnetic antenna, serial and antenna cables, voltage regulator, power supply, and backup battery for about $100. Which is probably what you'll end up spending on the ebay 50-meter special, once you add all the things that don't come with it.
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