On Thu, Sep 25, 2014 at 3:34 AM, Neil Schroeder <gign...@gmail.com> wrote: > Are all the devices you're using or considering capable of hardware > timestamps? Or are you doing it in software today?
The PPS from the GPS is timestamped fully in hardware using the "input capture" function of the hardware timer to copy its value to another register on a signal edge. The outgoing PPS is generated by the same timer. The NTP stuff relies on software; the receive timestamp is captured from the timer as early as possible in the Ethernet ISR, and the transmit timestamp is captured as the last thing before sending the packet to the MAC to be transmitted. It's not perfect, but it's as good as I'm likely to get right now. Some day I might look into whether I can integrate a PTP-capable Ethernet PHY :) Right now I have the UDOO board (which is no longer serving as the mainboard of the clock) running ntp on Linux with both the PPS and the NTP as sources; numbers from that forthcoming when I have them. Andrew _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
