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PMB-688 GPS and Arduino — Parallax Forums

PMB-688 GPS and Arduino

VamPVamP Posts: 17
edited 2010-06-20 12:50 in Accessories
I have both products (PMB-688 and Arduino).

I looked at the ... Small datasheet for the 688 and it didn't help; much.

If you look at the board you can see that the pins are labeled.
(left to right)
RX, TX, V, RXD, TXD, G.

From what I understand from the datasheet the "normal" RX and TX pins are not connected?
What are these for then? (just curious)
V I assume is the 3~5VDC.
G is obviously Ground.
RXD and TXD, are the Serial lines I am suppose to use?


Also I am pretty new to micro-controllers.
I have been playing around with them, but this is a little over my head.

How would you store this data?
Parse through it and save the fields in the given type? (int, float, char, etc)
or should I use a library for strings? Array?

All help is appreciated.
Information wants to be free! smurf.gif

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-09 14:29
    This is a support forum for Parallax products and neither of the products you mentioned are made by or carried by Parallax. That said, we'd be happy to help you with something as straightforward as trying to interpret information from a product's datasheet. Please furnish a link to a datasheet or manual for the PMB-688.

    GPS receivers produce standard format strings of data. Yes, you'd have to parse through them and save what information you want in the format you need them in. There are a lot of libraries of code for the Arduino. Check out the Arduino support website. You may find a library already written for handling GPS data.
  • hover1hover1 Posts: 1,929
    edited 2010-06-09 14:47
    Here is some documentation that does not show up on the product page:
    http://www.parallax.com/Store/Sensors/CompassGPS/tabid/173/CategoryID/48/List/0/SortField/0/Level/a/ProductID/645/Default.aspx
    Jim
    VamP said...


    I looked at the ... Small datasheet for the 688 and it didn't help; much.

    pdf
    pdf
    SiRFDemo_User_Guide.pdf
    2M
    pdf
    pdf
    SMIRF-NMEA_commands.pdf
    574K
  • Ken GraceyKen Gracey Posts: 7,392
    edited 2010-06-09 15:14
    The PMB 688 is a Parallax GPS unit from Polstar. It would be best to look at the BS2 or Propeller code examples.

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    Ken Gracey
    Parallax Inc.

    Follow me at http://twitter.com/ParallaxKen for some insider news.
  • hover1hover1 Posts: 1,929
    edited 2010-06-09 15:32
    @Ken,

    Sadly, there are no examples on the product pages, except for the original GPS. The demo runs in the Smart Mode. It does take some searching to find some.

    Jim
  • Mike GreenMike Green Posts: 23,101
    edited 2010-06-09 15:53
    Sorry to have gotten confused about the GPS module. If you look at the connection diagram for the PMB-248 module

    www.parallax.com/Portals/0/Downloads/docs/prod/sens/PMB-248%20GPS%20Receiver_A%20Schematic.pdf

    you'll see that there are two sets of RX/TX lines, one labelled RS232 and the other labelled TTL. The RS232 lines use RS232 voltage levels and are intended for direct connection to a PC's serial port (see the Wikipedia article on RS232 for details of the signals). The TTL lines use logic level signals (probably 3.3V/0V) for direct connection to a microcontroller like the Arduino or Basic Stamp.

    I believe the same connector is used for all the PMB series GPS modules.
  • Ken GraceyKen Gracey Posts: 7,392
    edited 2010-06-09 16:15
    I thought we had posted code examples. I will alert the Product Owner inside of Parallax.

    Thanks, Ken

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    Ken Gracey
    Parallax Inc.

    Follow me at http://twitter.com/ParallaxKen for some insider news.
  • TimmooreTimmoore Posts: 1,031
    edited 2010-06-09 16:26
    Take a look at this thread http://forums.parallax.com/showthread.php?p=912583
    , it talks about the 248 and 648, except for external antenna the 648 and 688 should be the same.

    There are gps examples on obex for the propeller.
  • electrosyselectrosys Posts: 212
    edited 2010-06-09 16:31
    VamP said: From what I understand from the datasheet the "normal" RX and TX pins are not connected?
    What are these for then? (just curious)
    There·are some·GPS modules,·that has two set of Tx/Rx, one is RS232 which can be connected to PC (HyperTerminal)
    and the other Tx/Rx is TTL level for connecting to the microcontroller (your GPS has only TTL pins)
    Look at GPS comparsion table·/Special Features/··PMB-248·and PMB-648·has both TTL and RS232 Pins, but PMB-688 has only TTL outputs.
    You could also use a MAX232 chip or two transistors ciruit·to convert the TTL to RS232, it is not a difficult task.

    For Arduino:
    Here·is·a some pages you could look at:
    How to make various things work with Ardunio··(and GPS module)
    Connecting·a Parallax·GPS to Arduino·
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2010-06-09 16:40
    Actually we should have had the following code uploaded to the PMB-648 and PMB-688 pages. This code is not compatible with the PMB-248 because of formatting changes, though I could make a version that is by changing some pointers in the code. For now, here is the GPS example code while we wait for it to appear on the product pages. Take care.

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    Chris Savage

    Parallax Engineering
    bsp
    bsp
    Easy GPS V1.0.bsp
    16K
  • hover1hover1 Posts: 1,929
    edited 2010-06-09 16:58
    Thanks Chris! That's going to help a lot of people!

    Jim
  • VamPVamP Posts: 17
    edited 2010-06-09 20:23
    Thanks guys!
    I have looked at the "easy" file.
    It is very neatly setup and would be a piece of cake... except I'm new to this. blush.gif
    I think what I will do is take all the information you guys have given me, and head over to the Arduino forum.

    At this point in time I am still pretty much a script kiddie when it comes to micro-controllers.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2010-06-09 22:15
    Well, if you have specific questions you can post them here. Be specific though and we can only answer in relation to our code, not the Arduino. [noparse];)[/noparse]

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    Chris Savage

    Parallax Engineering
    ·
  • Chuck McManisChuck McManis Posts: 65
    edited 2010-06-20 03:48
    I'm not sure how to tell which version of the GPS module I have, but I was wondering if I it was possible to access the 'pps' (pulse per second) that is available in the Sirf3 chipset ?
    I notice there are some pads that come off the embedded SX chip but I can't find any documentation on what they do.

    --Chuck
  • hover1hover1 Posts: 1,929
    edited 2010-06-20 12:50
    If you have the original Parallax GPS, Item Code 28146, then have a look at this article:

    http://www.parallax.com/dl/docs/cols/nv/vol7/col/NV139.pdf

    Jim
    Chuck McManis said...
    I'm not sure how to tell which version of the GPS module I have, but I was wondering if I it was possible to access the 'pps' (pulse per second) that is available in the Sirf3 chipset ?
    I notice there are some pads that come off the embedded SX chip but I can't find any documentation on what they do.

    --Chuck
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