| Electronics > Repair |
| Symmetricom NTS-200 Time Server |
| << < (16/17) > >> |
| YetAnotherTechie:
Hello, I've been following this thread and just have to ask... I saw on one of the datasheets above that the timing accuracy is at least 150ns plus a few millis once you add the other network overheads. There's been a lot of progress on GPS chipsets in the last 20(!) years, have you considered using a modern timing unit like ublox M8T and say a raspberry pi or similar? Don't get me wrong, i know and love fixing old gear, but i also consider the performance of the fixed unit and the usefulness of the knowledge i gain repairing it, and to me this units seem like a bad proposition? |
| smgvbest:
I have and use a Pi3 + ublox as a stratum 1 time source with fall back to ntp servers as a Stratum 2 time source. My usage is in Astronomy and keeping my PC set so that images have a accurate timestamp. for me this is a fun problem to solve, Just wanted to see if I could do it while learning some reverse engineering techniques. |
| acfnews:
Hi, Also totally aware of the (better) possibilities of other hardware. The remote site where the NTS-200 was located also has a newer GPS stratum1 timeserver used in an IoT gateway. The NTS-200 has more emotional value than technical value, and still I think messing around with it is a learning process... Best regards, Ron |
| smgvbest:
I have not fixed mine yet. I am convinced until you resolve the incorrect time coming from the P60ARM/GPS you're not going to have a reliable fix. Problem I have is my EPROM read does not read the 16bit eproms used by this controller nor does the JTAG interface support reading them from what I can tell. it has a limited JTAG version 1 implementation. I'm not a JTAG expert but even if I could get a dump of the memory i have no way to write new eproms. I did find the AT49F1025 are a pin compatible replacement but are also very hard to find and my programmer does not support them either. the 8 bit version yes, not the 16 bit version |
| InFoq:
--- Quote from: anenni on January 09, 2020, 09:14:32 pm ---I'm wondering if a linux ntpd or other daemon between nts200 and clients can correct the gps epoch correctly. --- End quote --- not a solution for everyone...but it was not too difficult to program NFQUEUE processes in C on my linux (running ntpd client) to do the timestamp offset corrections in each traffic direction. Turned out simplicity of NTP protocol being self-unaware enough to allow this to work quite well! Not sure how non-deterministic the OS's NFQUEUE mechanism is, but NTP's PLL corrections should not be much worse than for other worst-case internetworking jitters... E.g. MitM mangling set-top-box protocol: https://xakcop.com/post/mitm-stb/ |
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