120 lines
3.2 KiB
Groff
120 lines
3.2 KiB
Groff
.TH PHC2SYS 8 "November 2012" "linuxptp"
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.SH NAME
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phc2sys \- synchronize two clocks
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.SH SYNOPSIS
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.B phc2sys
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{
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.BI \-d " pps-device"
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[
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.BI \-s " phc-device"
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.BI \-i " interface"
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] |
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.BI \-s " phc-device"
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.BI \-i " interface"
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} [
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.BI \-c " phc-device"
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] [
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.BI \-P " kp"
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] [
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.BI \-I " ki"
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] [
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.BI \-R " update-rate"
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] [
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.BI \-N " clock-readings"
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] [
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.BI \-O " offset"
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] [
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.B \-w
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] [
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.B \-v
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]
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.SH DESCRIPTION
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.B phc2sys
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is a program which synchronizes two clocks in the system. Typically, it is used
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to synchronize the system clock to a PTP hardware clock (PHC), which itself is
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synchronized by the
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.BR ptp4l (8)
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program.
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Two synchronization modes are supported, one uses a pulse per second (PPS)
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signal provided by the source clock and the other mode reads time from the
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source clock directly. The PPS mode is usually preferred, because reading the
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PHC is slow and introduces an unknown error in the readings, but not all PHCs
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provide the PPS signal.
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.SH OPTIONS
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.TP
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.BI \-d " pps-device"
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Specify the PPS device of the master clock (e.g. /dev/pps0). With this option
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the PPS synchronization mode is used instead of the direct mode. As the PPS
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signal does not specify time and only marks start of a second, the slave clock
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should be already close to the correct time before
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.B phc2sys
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is started or the
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.B \-s
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option should be used too. This option can be used only with the system clock as
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the slave clock.
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.TP
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.BI \-s " phc-device"
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Specify the master clock by device (e.g. /dev/ptp0) or name (e.g. CLOCK_REALTIME
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for the system clock). When this option is used together with the
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.B \-d
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option, the master clock is used only to correct the offset by whole number of
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seconds, which cannot be fixed with PPS alone.
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.TP
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.BI \-i " interface"
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Similar to the
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.B \-s
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option, but specified by the interface which provides the master clock.
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.TP
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.BI \-c " phc-device"
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Specify the slave clock by device (e.g. /dev/ptp1) or name. The default is
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CLOCK_REALTIME (the system clock).
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.TP
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.BI \-P " kp"
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Specify the proportional constant of the PI controller. The default is 0.7.
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.TP
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.BI \-I " ki"
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Specify the integral constant of the PI controller. The default is 0.3.
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.TP
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.BI \-S " step"
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Specify the step threshold of the PI controller. It is the maximum offset that
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the controller corrects by changing the clock frequency instead of stepping the
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clock. The clock is always stepped on start. The value of 0.0 disables stepping
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after the start. The default is 0.0.
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.TP
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.BI \-R " update-rate"
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Specify the slave clock update rate when running in the direct synchronization
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mode. The default is 1 per second.
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.TP
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.BI \-N " phc-num"
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Specify the number of master clock readings per one slave clock update. Only
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the fastest reading is used to update the slave clock, this is useful to
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minimize the error caused by random delays in scheduling and bus utilization.
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The default is 5.
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.TP
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.BI \-O " offset"
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Specify the offset between the slave and master times in seconds. With the
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.B \-w
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option the default value is set automatically according to the currentUtcOffset
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value obtained from ptp4l and the direction of the clock synchronization.
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Without
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.B \-w
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the default is 0.
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.TP
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.B \-w
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Wait until ptp4l is in a synchronized state.
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.TP
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.BI \-h
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Display a help message.
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.TP
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.B \-v
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Prints the software version and exits.
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.SH SEE ALSO
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.BR ptp4l (8)
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