Rob Seaman wrote: > Dont know if this got through using my new email address. > > Have been rummaging around looking at Arduino and/or Raspberry Pi hacks, > but the former seems under-powered to run a full NTP instance and the > latter is not real-time.
If you want a cheap solution then maybe you should have a look at the Banana Pi and/or Beaglebone Black. The Raspberry Pi's NIC chip is internally connected via USB, which causes latencies and asymmetries for network packets, which in turn can decrease the accuracy you can yield via NTP. The Beaglebone Black and AFAIK also the Banana Pi have NIC chips which are connected directly to the CPU, not via USB, which avoids the latencies introduced by USB. Unlike the Beaglebone Black and the Raspberry Pi the Banana Pi also supports native 1000 MBit link speed. Eventually you don't have to transfer much data and 100 MBit sounds enough, but if your switch and your LAN run on 1 GBit and you connect a single 100 MBit device to one switch port then all packets from or to the slow port need speed conversion, which often means queuing by the switch, which in turn also inserts latencies affecting the resulting accuracy. In any case you need to spend some of your time to configure and test this properly, so as Warner has already mentioned in his reply, if you only need one or a few instances of those loggers it may be easier to buy a solution which is more expensive, but doesn't require lots of your time. So just for completeness I'd like to mention that most Meinberg GPS receivers provide 2 "time capture" inputs which directly capture the on-board UTC time derived from the stable on-board oscillator which is directly disciplined by the GPS input signal. You can apply 2 different hardware trigger signals. The captured time stamps are saved in an on-board FIFO buffer and can be retrieved via a serial port, or in case of a GPS PCI cards, directly via the PCI bus. Take care, I'm biased. ;-) Martin _______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
