[ntp:questions] NTP and ADAM

Martin Burnicki martin.burnicki at meinberg.de
Wed Feb 13 12:03:11 UTC 2008

noosh wrote:
> Martin Burnicki wrote:
>> Neither the GPS nor the ADAM are NTP servers, so why should a client find
>> it?
> if i do the following
>  GPS-------------------------------> PC(NTP)
>             Serial Port
> the time is synchronized by GPS.

Right. However the PC is your NTP server and the GPS device is just a
reference clock which is read by the GPS program running on the PC.

>> What might be possible is to configure the local NTP daemon to read the
>> "serial" ref clock via the converter's emulated port.
> What do u mean by that? how can i do that? can you give more detail of
> your idea?

In the figure above the GPS devices provides a serial port which is
connected to one of the PC's serial ports. The NTP program on the PC opens
that serial port and uses a special driver (e.g. the parse driver or the
NMEA driver) to read the time from the GPS clock, depending of the string
format send by the clock.

>From your initial post:
> this is my first time that i have to work with ADAM 4577. it is 1 port
> universial serial gateway.now it is like this
> GPS ----------------->ADAM 4577 --------------------------------->PC1
>            serial Port                             LAN
> unfortunatelly PC cann't find  ADAM as its NTP Server. has anyone work
> with this ADAM 4577?

So ADAM is a serial-to-LAN converter which reads the serial output of the
GPS receiver and puts those bytes into network packets which arrive at the
LAN port of your PC instead of a serial port. I assume the format of those
packets is proprietary since it must not only transport the raw byte stream
from the GPS device but also the levels of the GPS devices serial control

The NTP program can only receive NTP packlets from another NTP server, not
those proprietary ADAM packets. On the other hand, if you configure the NTP
daemon on your PC to use the GPS device as a reference clock (as you would
do without the ADAM) then ntpd tries to open the configureed serial port,
set the baud rate etc. correctly, and receive the string from the GPS

So if you want ntpd to read the serial time string from the GPS device then
you have to install a driver on the PC which receives the proprietary
network packets sent by ADAM, and appears like a serial device to the NTP
daemon. Those drivers are normally shipped with the device, at least for
Windows where they emulate a COM port e.g. COM20. You should see if the
ADAM device comes with a Linux driver at all.

And, please remember that network redirection of serial data introduces
additional jitter, so the results may not be too good.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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