Function PPSClockSync

phc/pps_source.go:231–262

PPSClockSync adjusts the frequency of the destination device based on the PPS from the ppsSource

(pi ServoController, srcTimestamp time.Time, dstEventTimestamp time.Time, dstDevice DeviceController)

// PPSClockSync adjusts the frequency of the destination device based on the PPS from the ppsSource
func PPSClockSync(pi ServoController, srcTimestamp time.Time, dstEventTimestamp time.Time, dstDevice DeviceController) error {
	phcOffset := dstEventTimestamp.Sub(srcTimestamp)

	err := validatePPSEvent(dstEventTimestamp, dstDevice)
	if err != nil {
		return fmt.Errorf("error validating event: %w", err)
	}
	freqAdj, servoState := pi.Sample(int64(phcOffset), uint64(dstEventTimestamp.UnixNano())) // unix nano is never negative

	log.Printf("%s offset %10d servo %s freq %+7.0f", dstDevice.File().Name(), int64(phcOffset), servoState.String(), freqAdj)

	switch servoState {
	case servo.StateJump:
		if err := dstDevice.AdjFreq(-freqAdj); err != nil {
			return fmt.Errorf("failed to adjust freq to %v: %w", -freqAdj, err)
		}
		if err := dstDevice.Step(-phcOffset); err != nil {
			pi.Unlock()
			return fmt.Errorf("failed to step clock by %v: %w", -phcOffset, err)
		}
	case servo.StateLocked:
		if err := dstDevice.AdjFreq(-freqAdj); err != nil {
			pi.Unlock()
			return fmt.Errorf("failed to adjust freq to %v: %w", -freqAdj, err)
		}
	case servo.StateInit:
		return nil
	default:
		return fmt.Errorf("skipping clock update: servo state is %v", servoState)
	}
	return nil
}

// PPSSinkFromDevice configures the targetDevice to be a PPS sink and report PPS timestamp events
func PPSSinkFromDevice(targetDevice DeviceController, pinIndex uint) (*PPSSink, error) {