[time-nuts] NTP jitter with Linux

Javier Herrero jherrero at hvsistemas.es
Thu Apr 5 12:20:06 UTC 2012


El 05/04/2012 12:20, Azelio Boriani escribió:
>>> On a side note, speaking of deterministic systems, why has no one built a
> GPSDO with an FPGA yet? Or an NTP server? :)
>
Oh, I've done that (an NTP server, not GPSO) in a Cyclone III FPGA. But 
well... it has a Nios-II CPU and runs Linux, so I suppose it does not 
count too much :). A pure FPGA (without CPU) NTP server would be very 
fun, but I suppose that the development effort required would not worth 
it, taking into account that implementing a true ntp in an embedded 
linux is quite easy. I have recently put into work an application that 
reads and writes UDP packets for a relatively high speed (280Mbps) 
ethernet to ECSS-E-ST-50-01C TM transfer frames gateway. The Ethernet 
part was quite easy to implement (the RAM-based FIFOs and flow and error 
control were a bit more difficult, since you must have a continous 
uninterrupted 280Mbps output, and the input is Ethernet - with extremely 
variable latencies).

Regards,

Javier






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