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  1. #1
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    Default Problem with writing commands to GP-635T

    Hi everyone,

    I am working on my senior design project at the University of Florida and part of our project involves using a GPS module. I am using the GP-635T, the link to the data sheet is below.

    This chip, relatively cheap, outputs standard NMEA messages at a rate of 1Hz and claims to be able to output messages up to 5 Hz. Here is where my question lies. I am using a terminal program to communicate with the chip called RealTerm:Serial/TCP Terminal, I also posted a link to their website below if you want to look into that.

    I am trying to send commands to the chip to disable all the NMEA message I do not need and increase the rate up to 5Hz. So far nothing is working. I have found Query/Rate control commands and a few PDF's that look helpful, but I still cannot change the output of the chip.

    My setup: I have a usb cable connected to a FTDI232 and a GP-635T with all the proper connections. Tx(gps)>Rx(ftdi) and Tx(ftdi)>Rx(gps). I know they are communicating because I can read the data coming from the GPS to the terminal screen, but when I try to write the commands to the gps I get the error message

    $GPTXT,01,01,01,PSRF inv format*2B<CR><LF>

    I am sending the code "$PSRF103,05,00,00,01*21" without the quotations with the <CR><LF> EOL through the terminal program and I am extremely confused because this is EXACTLY what the guides/manuals say.

    Any help is greatly appreciated. I will be out of town for a week or so after tomorrow, so if I don't respond immediately that is the reason. I will also post this in the general forum, sorry if this thread is misplaced.

    Thank you again,
    Alex


    Datasheet: [Only registered and activated users can see links. ]
    Terminal Program I'm using: [Only registered and activated users can see links. ]

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  3. #2
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    Default

    Hi. I'm not a specialist in this area so I can be arbitrarily wrong, but I can google.
    I've found that PSRF103 is a command for SIRF chips.
    Code:
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    And if you search for "SIRF" word on the following page you would start thinking that maybe GP-635T is not SIRF based.
    Code:
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    Also my intuition tells me that disabling some NMEA messages is not enough to increase the output rate and you should request the new baud rate by sending a specific command.
    And, yes, 9600/5/8 = 240 is not enough for the NMEA message group if all NMEA messages are enabled.
    My NMEA samples have ~400 chars per message group.
    Last edited by kunix; 27th February 2015 at 09:36.

  4. #3
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    Default

    Hey, thanks for the input, I'll look into other formats than SiRF... if I find anything I will post my solution here if I remember...

 

 

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