Convert PPS signal from BNC to RS-232! - NTP

This is a discussion on Convert PPS signal from BNC to RS-232! - NTP ; Hello. I have a Symmetricom Syncserver S250 as primary NTP-server. This box has PPS-output via a BNC connector. I need to get this PPS signal onto a rs232 connector. Are there any converter kits that can do this, or do ...

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Thread: Convert PPS signal from BNC to RS-232!

  1. Convert PPS signal from BNC to RS-232!

    Hello.


    I have a Symmetricom Syncserver S250 as primary NTP-server.
    This box has PPS-output via a BNC connector. I need to get this PPS signal
    onto a rs232 connector.

    Are there any converter kits that can do this, or do I need to make my own
    "box" for doing this?

    I have setup a secondary server (ntpd on FreeBSD) that will use PPS to
    discipline its clock via /dev/pps (on a serial com-port).

    Any hints on how to get the PPS from the BNC(coax)-output on the primary
    server to the com-port on the secondary server would be appreciated.

    - Erling Paulsen

  2. Re: Convert PPS signal from BNC to RS-232!

    Erling Paulsen writes:

    > Hello.
    >
    >
    > I have a Symmetricom Syncserver S250 as primary NTP-server.
    > This box has PPS-output via a BNC connector. I need to get this PPS signal
    > onto a rs232 connector.
    >
    > Are there any converter kits that can do this, or do I need to make my own
    > "box" for doing this?
    >
    > I have setup a secondary server (ntpd on FreeBSD) that will use PPS to
    > discipline its clock via /dev/pps (on a serial com-port).
    >
    > Any hints on how to get the PPS from the BNC(coax)-output on the primary
    > server to the com-port on the secondary server would be appreciated.


    I have seen many designs. One is at
    http://www.kernel.org/pub/linux/daem...LtoRS232.ps.gz and uses a
    CA3140E op-amt. Another is at
    http://www.eecis.udel.edu/~mills/ntp/html/pps.html, but dated
    1992. You can also use a MAX232.

    Hope this helps.

    Jon Kåre

  3. Re: Convert PPS signal from BNC to RS-232!


    >I have a Symmetricom Syncserver S250 as primary NTP-server.
    >This box has PPS-output via a BNC connector. I need to get this PPS signal
    >onto a rs232 connector.


    Just wire it up and give it a try. The PPS output is a good
    solid TTL signal. It will work fine unless you are going
    very long distances.

    Their data sheet says it will drive 50 ohms. If you have a scope
    handy, see what it looks like. Without a 50 ohm terminater, it
    is likely to be 2x the TTL level. Who knows what "TTL" means
    these days. It's probably CMOS, either from 5V or from 3.3V.

    --
    These are my opinions, not necessarily my employer's. I hate spam.


  4. Re: Convert PPS signal from BNC to RS-232!

    Hal,

    The orignal Bell 103/201/202 modem specification required a bipolar data
    signal +-6V or more. Later, the 113 modem specification allowed unipolar
    signals, but was not widely adopted. In some cases the modem or UART
    chip does work with TTL signals, but not all. It takes two transistors
    and a resistor to fix that, or better yet a MAX232 chip. Details are in
    the NTP documentation on the gadget box page.

    Dave

    Hal Murray wrote:

    >>I have a Symmetricom Syncserver S250 as primary NTP-server.
    >>This box has PPS-output via a BNC connector. I need to get this PPS signal
    >>onto a rs232 connector.

    >
    >
    > Just wire it up and give it a try. The PPS output is a good
    > solid TTL signal. It will work fine unless you are going
    > very long distances.
    >
    > Their data sheet says it will drive 50 ohms. If you have a scope
    > handy, see what it looks like. Without a 50 ohm terminater, it
    > is likely to be 2x the TTL level. Who knows what "TTL" means
    > these days. It's probably CMOS, either from 5V or from 3.3V.
    >


  5. Re: Convert PPS signal from BNC to RS-232!

    On Mon, 05 Mar 2007 16:03:41 +0000, David L. Mills wrote:

    > Hal,
    >
    > The orignal Bell 103/201/202 modem specification required a bipolar data
    > signal +-6V or more. Later, the 113 modem specification allowed unipolar
    > signals, but was not widely adopted. In some cases the modem or UART
    > chip does work with TTL signals, but not all. It takes two transistors
    > and a resistor to fix that, or better yet a MAX232 chip. Details are in
    > the NTP documentation on the gadget box page.
    >


    Around 99.9% of all RS232 interfaces on a PC will detect a zero as a
    voltage below somewhere in the region of 1-2V and a one as anything above
    that. If it where not so my receiver would not work, but it does

    http://www.buzzard.me.uk/jonathan/radioclock.html


    JAB.

    --
    Jonathan A. Buzzard Email: jonathan (at) buzzard.me.uk
    Northumberland, United Kingdom. Tel: +44 1661-832195


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