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Cheap GPS — Parallax Forums

Cheap GPS

Jim FouchJim Fouch Posts: 395
edited 2010-06-22 20:24 in General Discussion
I got some spam today from Buy.com which I have bought from before and they're·decent.

Anyway one of the items was USB GPS for a laptop. I ordered one on the chance that I can hack into on the other side of the USB interface. I'm guessing there is just a USB to serial adapter chip in the cable.

If it works out·it's a steal for $13 w/ free shipping.

http://enews.buy.com/cgi-bin5/DM/y/nszA0Jq2co0QPb0Cgfe0GY

Update: I just checked the·link again and they are sold out. But maybe worth a google search and see if anyone else is selling them cheap.

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Jim Fouch

FOUCH SOFTWARE

Comments

  • Jay KickliterJay Kickliter Posts: 446
    edited 2009-12-16 00:33
    Have any idea what chip they're using?
  • Jim FouchJim Fouch Posts: 395
    edited 2009-12-16 01:01
    Not sure. But it should be pretty easy to probe it with a logic analyzer and look for serial traffic. I'll let you know after I get the device. If nothing else I can still use it with my netbook. smile.gif

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    Jim Fouch

    FOUCH SOFTWARE
  • RickBRickB Posts: 395
    edited 2009-12-17 16:00
    $10 gps. http://www.weirdstuff.com/cgi-bin/category.cgi?item=20164#
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-12-17 17:54
    The $10 does not include an antenna.

    -Phil
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2009-12-18 15:39
    $10 for the GPS and $13 for shipping... what's this world coming to?
  • FranklinFranklin Posts: 4,747
    edited 2009-12-18 16:53
    I'll sell it to you for $15 for the GPS and $13 for shipping if it will make you feel any better [noparse];)[/noparse]

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    - Stephen
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2009-12-30 05:01
    Ug, I have it in hand now and the datasheets provided by weirdstuff do not match the pinout at all. I managed to find all the GND pins with a probe (not one where the datasheet says they should be). But I can't find Vcc at all. Good thing they were only $10 'cause I see smoke in my future...

    ---

    (This is what one gets for being a TIIIIGHTWAAAAD!!!)
  • mikedivmikediv Posts: 825
    edited 2009-12-30 17:17
    Shmoopy,,LMAO tightwad,, I was going to get one let us know if you figure it out I wanted to get into the GPS stuff for my BoeBot but it just seemed to pricey but 20 something bucks would work for me if the device works
    Oh one last question I am confused does the one you have have an antenna?
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2009-12-31 01:33
    I've all but given up on it. The info links on the product page are both for a totally different model. Google has no data on this one (the TU00-D200). All I find is several other people looking for data. Sparkfun has a 3.3v active antenna with the right connector for ~$13.

    Like I said, I was able to find all five ground pins easily. And two different pins that seem to energize both crystals on the board and some of the vcc pins on several chips when +5V is connected. But there's also a master reset pin that needs to be tied high, and two option pins that need to be one low and the other high. This is assuming this model has any similarity to the data weirdstuff links to. Heck, with no datasheet, the rest of the pins could be some kind of parallel interface for all anyone knows.

    I have two, PM me your address and I'll mail one to you.
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-05 06:34
    IT'S ALIVE! IT'S ALIVE!

    After 3 hours of poking it with a continuity checker and Googling data sheets I have the Rockwell GPS alive and emitting serial data and 1PPS! Next hurdle is to figure out what serial data it's spewing out because it's certainly not ASCII, or it's at some funky speed or configuration. If anyone's interested, here's the pinout I've found so far.

    1 - Ant Pwr
    2 - VCC
    3 - GND
    4 - ? (floats lo)
    5 - Battery backup to DS1302 RTC
    6 - Serial OUT
    7 - 1PPS
    8 - ? (floats lo)
    9 - ? (floats hi)
    10 - Battery backup to MAX704 (and then to sram maybe)
    11 - GND
    12 - ? (floats lo)
    13 - Master Reset (This needs to be tied high, not floating.)
    14 - GND
    15 - ? (floats lo)
    16 - ? (floats hi)
    17 - GND
    18 - ? (floats hi)
    19 - GND
    20 - ? (floats hi)

    Post Edited (Shmoopy) : 1/5/2010 6:39:48 AM GMT
  • RickBRickB Posts: 395
    edited 2010-01-05 15:44
    Is there any indication that 10 KHz is present on one of the pins?
    The serial data will be ttl and may be inverted. To not be ascii would be very strange.
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-05 18:02
    Sorry, I don't find 10KHz on any of the pins. There's some possibility that it can be configured that way, but not likely. The serial data is indeed inverted TTL, i have it piped through a MAX232 chip. Logic 1 =-10v : 0 = +10v, with idle at logic 1, correct? That's what I see when I loop back RX to TX on the MAX232 and type on Parallax Serial Terminal. I suspect the unit is defaulting to a binary serial protocol because one or more of the control pins are floating. This was the problem I had with the !MR pin, it doesn't like to float.

    Does anybody know any tricks to diagnosing serial communications without an expensive logic analyzer?
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-05 19:41
    Progress being made:

    Confirmed that the unit is sending Rockwell Binary Format data at 9600bps. This may good for my application because it eliminates the need for ASCII conversion.
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-05 20:14
    Process done! Finally found someone in China with the datasheets for this exact model. Attached below are what you'll need to get the board connected to your circuit. The full datasheet PDF is a smidge too big to attach in the forum. PM me for it.

    -MH
    pdf
    pdf
    gps2a.pdf
    36K
    pdf
    pdf
    gps2b.pdf
    30K
  • RickBRickB Posts: 395
    edited 2010-01-06 16:30
    Shmoopy:
    What was your searching technique? I spent more time than I care to think about trying to find the correct data for this unit.
    Real bummer about the lack of 10KHz.

    Rick
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-06 16:51
    I found someone on eBay selling the same TU00-D200 and asked him for the specs. He emailed them to me. It meant a lot of wasted time with the continuity checker my part, but it was fun anyway.

    Next step, find a tightwad compatible antenna rolleyes.gif

    Post Edited (Shmoopy) : 1/6/2010 5:03:21 PM GMT
  • kf4ixmkf4ixm Posts: 529
    edited 2010-01-06 16:59
    hows $6 for a cheap antenna?....
    http://www.google.com/products/catalog?sourceid=navclient&rlz=1T4ACAW_enUS313US313&q=gps+antenna&um=1&ie=UTF-8&cid=14764762512904657686&ei=ssFES6qsLMmzlAfcgo2mBw&sa=X&oi=product_catalog_result&ct=image&resnum=4&ved=0CCoQ8gIwAw#
    ·
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-06 17:02
    kf4ixm said...
    hows $6 for a cheap antenna?....

    Tightwad approved! thanks! hop.gif
  • kf4ixmkf4ixm Posts: 529
    edited 2010-01-06 17:13
    or even better,..... FREE! (or at minimum, the cost for a couple of pieces of copper clad and coax).

    http://www.express-builder.com/docs/gpsant/

    here's even a better design, it's a little big and gawky, but has much better sensitivity, especially for sats closer to the horizon. as with the patch design, it basically just looks straight up, (or whatever direction you have it pointed). this design uses a turnstile configuration, i've used this design before for we-fax weather satellite reception and you just can't beat it!

    http://www.arrl.org/tis/info/pdf/0210036.pdf






    Post Edited (kf4ixm) : 1/6/2010 5:48:54 PM GMT
  • Jim FouchJim Fouch Posts: 395
    edited 2010-01-20 19:31
    UPDATE: The cheap one I ordered came, but once I took it apart it does not seem to have a USB to Serial converter inside. Well, not easily accessible. It's still a good deal for $12, just not one I can use with the Prop. :-(

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    Jim Fouch

    FOUCH SOFTWARE
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-20 21:26
    Jim, which one did you order? Are your referring to an antenna, or complete GPS module?
  • Jim FouchJim Fouch Posts: 395
    edited 2010-01-20 21:33
    The one I posted at the top of the thread. I'm sure it works fine in a PC/Laptop, but I does not seem to have the FTDI chip that I was going to try to interface on the device side. I ordered it just on a hunch. The unit is sealed and only the USB cable is exposed. So whatever TTL<->USB chip they have is inside of the sealed area. :-(

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    Jim Fouch

    FOUCH SOFTWARE
  • FranklinFranklin Posts: 4,747
    edited 2010-01-21 02:16
    That's what hammers are for. (along with buying two or three of your first foray into unknown territory).

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    - Stephen
  • noovasnoovas Posts: 2
    edited 2010-06-21 18:56
    Hello there, I am a new here, I was googling for TU00-D200 GPS, and this is how I get here.... few days ago I received my second TU00-D200 GPS from exactly the same person on Ebay, I bought and antenna from him. The problem is that the GPS (both of them) only sends ($GPGGA,,,,,,0,00,,,,,,*66) to my PC. When I tried my first GPS from him I was thinking that the problem comes form the antenna (first antenna I was using was from another Ebay seller ) or from the analog input of the GPS, because it was sending only ($GPGGA,,,,,,0,00,,,,,,*66), I am waiting more than 30min.... nothing. So I bought another GPS from the same person but this time and antenna from him. The second GPS is sending the same data like the first one. Now I dont know what to do... with two GPSs and two antenas , and cant make them run. Here are the pins which I have connected:
    pin2 - +5V
    pin3 - GND
    pin4 - +5V (NMEA)
    pin6 - data out
    pin9 - data in
    pin11 - GND
    pin13 - +5V (master reset)
    pin14 - GND
    pin17 - GND
    pin19 - GND
    pin20 - GND (for 4800bps)

    This is how I was trying to run the GPSs at first time.


    Today I was trying with connecting +5V to pin 10, then +5V to pin 5, and after that +5V to both of them pin5 and pin10. I think it should work and without this two connections, but I am trying everything now..... dont know what to try now..... if you see what I am doing wrong or missing pls HELP!!!!
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-21 19:43
    The antenna needs power too, so you have to power pin 1 with 3.3 to 5 volts as well. My pinout is:

    1: +5 (ant)
    2: +5 (Vcc)
    3: GND
    4: +5 (NMEA) - GND or float (BINARY) I have a jumper here.
    5: NC
    6: Serial out
    7: 1PPS out
    8: NC
    9: Serial in
    10: ~4.8v from supercap (only helps in binary mode)
    11: GND
    12: NC
    13: +5
    14: GND
    15: NC
    16: NC
    17: GND
    18: NC
    19: GND
    20: GND (4800b) +5 or float (9600) I have a jumper here
  • hover1hover1 Posts: 1,929
    edited 2010-06-21 20:50
    @Martin,
    Are you using your unit with good reliability? I may pick one up since they are still available.
    Jim

    PS Could I get the full data sheet? PM sent.

    Post Edited (hover1) : 6/21/2010 8:56:24 PM GMT
  • noovasnoovas Posts: 2
    edited 2010-06-22 18:03
    THANKS a lot it is working now!!!! 10x [noparse]:)[/noparse]
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-22 20:24
    @hover1

    I have only been using the unit for <1s accurate timestamps. Sorry I don't have any data on the spatial (geodetic?) accuracy. But at $10, go ahead and give it a try.
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