148 lines
4.6 KiB
C
148 lines
4.6 KiB
C
/**
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* @file servo.h
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* @brief Implements a generic clock servo interface.
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* @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef HAVE_SERVO_H
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#define HAVE_SERVO_H
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#include <stdint.h>
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/**
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* When set to a non-zero value, this variable controls the maximum allowed
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* offset before a clock jump occurs instead of the default clock-slewing
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* mechanism.
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*
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* Note that this variable is measured in seconds, and allows fractional values.
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*/
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extern double servo_step_threshold;
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/**
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* When set to zero, the clock is not stepped on start. When set to a non-zero
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* value, the value bahaves as a threshold and the clock is stepped on start if
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* the offset is bigger than the threshold.
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*
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* Note that this variable is measured in seconds, and allows fractional values.
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*/
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extern double servo_first_step_threshold;
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/**
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* When set to a non-zero value, this variable sets an additional limit for
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* the frequency adjustment of the clock. It's in ppb.
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*/
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extern int servo_max_frequency;
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/** Opaque type */
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struct servo;
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/**
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* Defines the available servo cores
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*/
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enum servo_type {
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CLOCK_SERVO_PI,
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CLOCK_SERVO_LINREG,
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CLOCK_SERVO_NTPSHM,
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CLOCK_SERVO_NULLF,
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};
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/**
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* Defines the caller visible states of a clock servo.
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*/
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enum servo_state {
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/**
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* The servo is not yet ready to track the master clock.
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*/
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SERVO_UNLOCKED,
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/**
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* The is ready to track and requests a clock jump to
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* immediately correct the estimated offset.
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*/
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SERVO_JUMP,
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/**
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* The servo is tracking the master clock.
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*/
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SERVO_LOCKED,
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};
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/**
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* Create a new instance of a clock servo.
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* @param type The type of the servo to create.
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* @param fadj The clock's current adjustment in parts per billion.
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* @param max_ppb The absolute maxinum adjustment allowed by the clock
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* in parts per billion. The clock servo will clamp its
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* output according to this limit.
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* @param sw_ts Indicates that software time stamping will be used,
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* and the servo should use more aggressive filtering.
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* @return A pointer to a new servo on success, NULL otherwise.
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*/
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struct servo *servo_create(enum servo_type type, int fadj, int max_ppb, int sw_ts);
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/**
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* Destroy an instance of a clock servo.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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*/
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void servo_destroy(struct servo *servo);
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/**
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* Feed a sample into a clock servo.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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* @param offset The estimated clock offset in nanoseconds.
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* @param local_ts The local time stamp of the sample in nanoseconds.
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* @param weight The weight of the sample, larger if more reliable,
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* 1.0 is the maximum value.
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* @param state Returns the servo's state.
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* @return The clock adjustment in parts per billion.
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*/
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double servo_sample(struct servo *servo,
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int64_t offset,
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uint64_t local_ts,
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double weight,
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enum servo_state *state);
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/**
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* Inform a clock servo about the master's sync interval.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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* @param interval The sync interval in seconds.
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*/
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void servo_sync_interval(struct servo *servo, double interval);
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/**
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* Reset a clock servo.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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*/
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void servo_reset(struct servo *servo);
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/**
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* Obtain ratio between master's frequency and current servo frequency.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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* @return The rate ratio, 1.0 is returned when not known.
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*/
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double servo_rate_ratio(struct servo *servo);
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/**
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* Inform a clock servo about upcoming leap second.
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* @param servo Pointer to a servo obtained via @ref servo_create().
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* @param leap +1 when leap second will be inserted, -1 when leap second
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* will be deleted, 0 when it passed.
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*/
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void servo_leap(struct servo *servo, int leap);
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#endif
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