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Related

gps logger 10hz

Former Member
Former Member over 13 years ago

Hi my name is Leonardo and I`m new in this and I was wondering if anyone can help me with a little problem I have with my gps logger.

 

I`m using a venus gps, an arduino uno rev3, a mpu6050 and a sd shield. The gps logs perfectly when it is set to 1hz but when puting it at 10hz, strange simbols appears inthe gps data lines in the file logged.

It is not allways and it is only in the gps data part, the mpu6050 is ok.

 

Does anyone knows why this could be?

 

The file is attached, notice that only the gps part has those strange characters

Attachments:
LOGGER00.CSV.zip
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  • shabaz
    0 shabaz over 13 years ago

    This is just a guess, so I may be wrong:

    I'm not knowledgeable with arduino (or GPS), but it may be worth checking the baud rate. If it is set very low (e.g. 4800bps), then this may be

    insufficient for 10Hz.

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  • nabhi
    0 nabhi over 13 years ago in reply to shabaz

    It is the problem with the baud rate. You see the total record length. Calculate the number of bits in a full record. See what is the baud rate set. Calculate whether 10Hz is ok or not You should be able to read the full record in 100ms. If u try to update faster than the read of port, then the garbage comes in.

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  • Former Member
    0 Former Member over 13 years ago

    By full record you mean the amount of bits in 1 second or the amount of bits in one line of data?

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  • shabaz
    0 shabaz over 13 years ago in reply to Former Member

    I think you can guesstimate, e.g. assuming that the GPS string is (say) 60 characters long, (and there are 8 bits per character) then that consumes 60*8 = 480bits. Now ten of those per second gets you to 4800 bits-per-sec, and this means that it is highly likely that you do need a higher bitrate than 4800, because the 60 was a guess (it may be 70 or more).

     

    However, I still don't know if that is the cause, it is just a hunch. What is the current baud setting? Is it 4800, 9600 or higher?

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  • Former Member
    0 Former Member over 13 years ago

    the baudrate is set to 38400 that is the baudrate for 10hz for the venus gps, so the serial.begin for the sketch is also in 38400, I have tryed with 115200 for the serial.begin for the sketch and its the same result.

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  • shabaz
    0 shabaz over 13 years ago in reply to Former Member

    The fact that it is higher than 4800 baud rules out this theory.

    38400 should be more than sufficient.

    It could be that the microcontroller is running with a non-crystal (i.e. non-accurate) oscillator, and maybe the problem was still there at 1Hz, but

    occurred less frequently, since most of your .csv file seems to contain correct data, with few rows containing incorrect

    data.

    At 1Hz, were you using 38400 baud too, or a lower value?

    You probably need to post an image or link to the arduino microcontroller board that you're using.

    Also, I don't know the implementation of the UART API in arduino; maybe you're overrunning a buffer due to the higher bitrate.

    Unfortunately, someone more experienced in Arduino may need to respond to you to help find the problem.

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