GPS problems

I cannot see any activity to thw GPS receiver, although it was working perfectly some days before. The receiver is located directly to a clear sky view.
There is a 3.6V DC at the output of Kiwi, and at the end of the cable (just before GPS receiver). I've changed the receiver with a new one, but the problem is the same.... GPS is always searching for signals, but without any result.
Has anybody else faced such a problem so far?

Comments

  • jksjks
    Accepted Answer
    I checked a number of locations running v1.84 and known to have GPS reception and they were all working fine.

    When you look at the GPS tab on the admin page what sort of activity do you see? At the bottom left does the "acq" value say "paused" or "yes"? Does any SNR value go over 15 such that a channel begins to show an RSSI value? If it does do you ever see any numbers appear in the "hold" column?

  • Please have a look..

    Capture.JPG
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  • Everything was just fine before 2-3 days. I thought that GPS came with the KIWI was damaged, I have placed a new one, but with the same results.

  • jksjks
    Accepted Answer
    That looks very much like it would if there were no GPS antenna connected. Do you have another active GPS antenna to try? I've had one other report of the antenna provided by Seeed failing after some time. How old is yours?

  • I;ve already placed a new antenna, with the same results.
    I've bought kiwi on February.
  • GPS output gives 3.6 V and the same currency is at the other end of the coaxial, just before the antenna. So, there are not any coaxial problems.
  • jksjks
    Accepted Answer
    Oh, okay. When you said "placed a new one" you meant a new GPS antenna. I thought you meant a new Kiwi. I assume the new antenna is also an active 3.3V type (most active ones accept 3-5V).

    Well, I'm not sure what to suggest. If you have a scope and a steady hand you could check the GPS front-end chip output test points. Give me a minute and I will put on the website the troubleshooting guide I gave to the Seeed factory. That will show you how to check the voltages and signals of the GPS section of the board.

  • jksjks
    edited May 19 Accepted Answer
    Here is the troubleshooting guide: http://www.kiwisdr.com/ks/troubleshooting.pdf
    Also available from the kiwisdr.com main page.

  • Check for the voltages is OK. All of them.
    Maybe I have to live without GPS....
  • This is the last screen, after a restart. "Search" last few seconds and then stoped again..

    Capture.JPG
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  • jksjks
    Accepted Answer
    What about the waveforms on the GCLK/GSGN/GMAG test points? This would tell us the overall condition of the GPS front-end chip and TCXO.
    If a voltage measurement on GCLK is around 1.6V then it's probably a clock signal as that is the average of a clock switching between 0 and 3.3V.

  • I don't have an oscilloscope.
    The voltage measurement on GCLK is 0.91V
  • Check points voltage:
    • 5V IN = 4.78 V.
    • 5VE = 4.59 V.
    • 5V = 4.63 V.
    • 3.3V = 3.44 V.
    • 1V = 0.99 V.
    • 1.8V = 1.8 V.
    • 3.3A = 3.29 V.
    • 3.3G - 3.31 V.
    • 3.3V GPS = 3.26 V. 
    daniel
  • jksjks
    Accepted Answer
    That's what I measure on GCLK. I also get 1.3V on GSGN and 0.8V on GMAG (all with no antenna attached).
    Did you buy this unit from Seeed? At this point I would ask for a warrantee repair / replacement.

  • edited May 20
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    • jksjks
      Accepted Answer
      You should have no problem with warrantee support from WiMo. If you do please let me know.

    • 1.42 V on GSGN 
      and 0.85 V on GMAG
    • What I Have to do? Shall I communicate with them and ask for a replacement?
      Are you going to inform them about the problem?
    • Yes, you have to ask them directly as the customer of the purchase.

    • THX a lot!. I'll keep you informed.
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