Function ActivatePPSSource

phc/pps_source.go:113–160

ActivatePPSSource configures the PHC device to be a PPS timestamp source

(dev DeviceController, pinIndex uint)

// ActivatePPSSource configures the PHC device to be a PPS timestamp source
func ActivatePPSSource(dev DeviceController, pinIndex uint) (*PPSSource, error) {
	err := dev.setPinFunc(pinIndex, unix.PTP_PF_PEROUT, defaultTs2PhcChannel)
	if err != nil {
		log.Printf("Failed to set PPS Perout on pin index %d, channel %d, PHC %s. Error: %s. Continuing bravely on...",
			pinIndex, defaultTs2PhcChannel, dev.File().Name(), err)
	}

	ts, err := dev.Time()
	if err != nil {
		return nil, fmt.Errorf("failed (clock_gettime) on %s", dev.File().Name())
	}

	// Initialize the PTPPeroutRequest struct
	peroutRequest := &PtpPeroutRequest{}
	peroutRequest.Index = uint32(defaultTs2PhcChannel)
	peroutRequest.Period = PtpClockTime{Sec: 1, Nsec: 0}

	// Set flags and pulse width
	pulsewidth := defaultPulseWidth

	// TODO: skip this block if pulsewidth unset once pulsewidth is configurable
	peroutRequest.Flags |= ptpPeroutDutyCycle
	peroutRequest.On = PtpClockTime{
		Sec:  int64(pulsewidth / 1e9),
		Nsec: pulsewidth % 1e9,
	}

	// Set phase or start time
	// TODO: reintroduce peroutPhase != -1 condition once peroutPhase is configurable
	peroutRequest.StartOrPhase = PtpClockTime{
		Sec:  ts.Unix() + ppsStartDelay,
		Nsec: 0,
	}

	err = dev.setPTPPerout(peroutRequest)

	if err != nil {
		peroutRequest.Flags &^= ptpPeroutDutyCycle
		peroutRequest.On = PtpClockTime{}
		err = dev.setPTPPerout(peroutRequest)

		if err != nil {
			return nil, fmt.Errorf("error retrying PTP_PEROUT_REQUEST2 with DUTY_CYCLE flag unset for backwards compatibility, %w", err)
		}
	}

	return &PPSSource{PHCDevice: dev, state: PPSSet, PPSPinIndex: pinIndex}, nil
}

// Timestamp returns the timestamp of the last PPS output edge from the given PPS source
func (ppsSource *PPSSource) Timestamp() (time.Time, error) {