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GPS versus GPS + cable — Parallax Forums

GPS versus GPS + cable

Dtom26Dtom26 Posts: 24
edited 2010-01-18 19:36 in Accessories
Can anyone tell me why the GPS is sold for 79.99 and the GPS + Cable is sold for 39.99?
Does the one with the cable offer less? Are the GPS's the same?

Comments

  • dandreaedandreae Posts: 1,375
    edited 2009-07-14 14:56
    The $79 version has a microcontroller on board that supports specific user-requested data via serial command interface and RAW mode information.· The PMB-248 GPS Receiver + Cable supports only NMEA0183 V2.2 data protocol.

    Dave



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    Dave Andreae

    Parallax Tech Support·
  • Dtom26Dtom26 Posts: 24
    edited 2009-07-14 15:13
    Which could I use if I just needed x,y coordinates?
    And needed to send that information via email or sms
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-07-14 16:02
    Hello,

    If you are referring to Latitude & Longitude either unit will provide that. The difference is in the interface and the way the data is presented. The Module has a co-processor and is designed for microcontrollers such as the BASIC Stamp 2 which does not have the resources to handle the large NMEA strings. That module also runs from a 5V supply. The receiver can run from 3.3V-5V and has both RS-232 and line level I/O, but it only outputs raw NMEA data. This means the microcontroller needs to buffer and parse the data to extract the Latitude and Longitude data from it. Take care.

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    Chris Savage
    Parallax Engineering
  • Dtom26Dtom26 Posts: 24
    edited 2009-07-14 17:32
    So because I have a Basic Stamp, I have to use the more expensive one? or the microcontroller has a more of a job to do if I use the 39.99 one?
  • Mike GreenMike Green Posts: 23,101
    edited 2009-07-14 18:18
    The BS2 does not have enough memory to process the raw NMEA strings. Other Stamp models have what's called scratchpad ram which can be used to buffer the raw NMEA data, but processing the data and extracting things like latitude and longitude is fairly complex and slow. The co-processor handles the buffering and the data extraction for the Stamp.

    So, in summary, if you have a BS2, you will need the more expensive GPS module. If you have some other Stamp model like the BS2sx, BS2p, BS2pe, or BS2px, you could use the cheaper module, but the programming will be much more complex and it will be slower.
  • Dtom26Dtom26 Posts: 24
    edited 2009-07-14 18:35
    Understood Thanks! =)
  • Scott4Scott4 Posts: 45
    edited 2010-01-18 19:36
    You may have already moved past the need for this information but the Parallax (Micomega) 32-bit Floating Point Coprocessor V3.1 can do all the NMEA sentence buffering and parsing and has I2C, SPI and·serial·interfaces. On Micromega's·application page they show you how to get GPS data using only their processor, a GPS and a display. I would also like to say that I·e-mailed Micromega·a question about using their processor and got back a very clear, complete and timely answer. I was very impressed! -Scott
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