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    Clock Synchronization with FPGA

    I am a bachelor student and I am assigned with a task to synchronizing measuring components clock with fpga.
    So far my in my research in the internet, I find that one of the solution to accomplish it is by synchroniying with GPS clock signal.

    My questions are :
    1. Is it possible to actually synchronize FPGA clock with GPS clock? If it is possible what kind of protocol should i use to achieve accuracy of 100ns?
    2. Is there any other option available which can give the same result as the GPS solution?

    Thank you.

    •   Alt7th February 2017, 13:58

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    Re: Clock Synchronization with FPGA

    From your questions it's clear you have no clue about who's who.
    Try to ask something specific.



    •   Alt7th February 2017, 23:22

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    Re: Clock Synchronization with FPGA

    I did not understand what you mean exactly, but u can use some GPS Modules that have a 10MHz external out clock and it can be used as a clock source for FPGA.
    u can use it to make some other clocks using DCM Module inside FPGA.


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    •   Alt11th February 2017, 20:31

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    Re: Clock Synchronization with FPGA

    Depending on the FPGA 10 MHz may be below the lowest allowed input frequency to a DCM.


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    Real Time Clock Synchronization using FPGA

    Okay I am assigned with a task to design a board for clock synchronization using FPGA.
    We want to get the time and clock from gps receiver from U-Blox LEA-M8T.
    The GPS receiver provide 4 types of communication protocols, UART, USB, SPI, DDC.

    The question is, in order to keep the data transfer between GPS and FPGA in real time, which protocol should I use? The question maybe unclear, can you please tell me what do you want to know in order to get a clearer view about the question.

    If I want to implement SPI protocol, do MISO and MOSI on SPI protocol can be connected to standard IO pin on the FPGA? I read that there are dedicated SPI pins, however I do not understand what differ these dedicated pins with the standard pins. Can someone please tell me the difference?

    If the only thing we actually need in our application is the second part of the current time (the Hour, date, etc. can be acquired from internet), is it possible to just take the timepulse and then connect it to the digital IO pins on the FPGA directly? So there will be no need to use any communication protocol.

    Okay from my questions it is clear that I am not sure about this and that since I am new. I would really appreciate if you can be patient with me. Thanks a lot.

    Best regards,

    RH



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    Re: Clock Synchronization with FPGA

    If I want to implement SPI protocol, do MISO and MOSI on SPI protocol can be connected to standard IO pin on the FPGA?
    Yes.
    I read that there are dedicated SPI pins, however I do not understand what differ these dedicated pins with the standard pins. Can someone please tell me the difference?
    Perhaps some Lattice FPGA's or other Vendor's SOC FPGA have a hardened SPI block in-silicon - and therefore also dedicated SPI pins.
    But this certainly isn't the general case.
    SPI is most often used for low/medium data rate transfer (<50Mbs).

    Modern FPGAs can easily handle such speeds on their GPIO's (or LVDS GPIO pairs if necessary).
    If the only thing we actually need in our application is the second part of the current time (the Hour, date, etc. can be acquired from internet), is it possible to just take the timepulse and then connect it to the digital IO pins on the FPGA directly? So there will be no need to use any communication protocol.
    Probably. but a communication protocol gives you much more flexibility...It's like comparing smoke signaling VS E-mail.

    You shouldn't be afraid to get your hands dirty. This forum will be of great help if you ask specific question.
    Last edited by shaiko; 17th February 2017 at 18:43.



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    Re: Clock Synchronization with FPGA

    The question is, in order to keep the data transfer between GPS and FPGA in real time, which protocol should I use?
    as I know, this modules ,by default, send Time/Date information every 1 second on UART. also they have a 1PPS signal that indicates the start of a second. by using Time/date information coming from UART u can extract time in a resolution of 1 second and by using 1PPS signal and counting by 10MHz signal u can reach higher resolutions like ms, us,nano second ,...



    •   Alt19th February 2017, 08:18

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    Re: Clock Synchronization with FPGA

    U-Blox LEA-M8T is in fact more than a basic GPS receiver, it's a full featured satellite navigation timing module that provides , already the generation of a synchronized clock signal with programmable frequency, much more than pps.

    So the answer to the questions is roughly: Yes you can do anything that you want with LEA-M8T and a FPGA, but you need to specify exactly what it is.

    A GPS synchronized clock (possible) is a different thing than an absolute GPS synchronized time (also possible), Combining different clock sources, as mentioned in your last post, doesn't automatically synchronize them correctly. In my view, it would be straightforward to use exclusively GPS time. But you didn't yet specify what's the intended absolute timestamp accuracy.



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