Changes in Version 2 of GraspExtrasSoftwareControllerNTP
- crae
- Timestamp:
- Wed Oct 10 13:43:50 2012
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GraspExtrasSoftwareControllerNTP
v1 v2 1 1 '''[wiki:GraspExtrasSoftware STARGRASP NTP client]''' 2 2 [[TracNav(GraspExtrasContents)]] 3 3 As of SVN revision 4427 of the stage 2 software, the STARGRASP controller has included experimental support for synchronising with an NTP server to provide timing for various events. The client can be started via the '''[wiki:GraspSwControllerCmdNtp ntp]''' command. 4 4 == Startup Performance == 5 Graph showing time offset when client starts, settling time, etc. 5 When first started, the NTP client first sets the system time from the first NTP transaction in a single step. Since it cannot make any assumptions about the system's clock drift, it initially starts with a drift correction of zero and attempts to figure out the drift from first principles over successive updates. The result is an initial overshoot that's typically on the order of a couple of milliseconds (the vertical scale below is in usec): 6 7 [[Image(stargrasp_ntp_startup.png)]] 8 9 After a couple of minutes, the NTP client typically settles to an NTP offset in the region of 100-200 usec, barring perturbations from the NTP server. 6 10 == Stargrasp Client: Observed Stability == 7 11 Show time offset when connected to NTP server via 100Mbit and Gigabit, long-term stability, etc. 8 12 == Linux NTP Daemon: Observed Stability == 9 13 Show how unstable linux NTP can be?