Ptp Configuration Features; Related Gige Vision Features - Teledyne FLIR A68 Series User Manual

PTP Grandmaster Clock
A PTP grandmaster clock is an external device that can provide a high precision clock
source to the other PTP-enabled devices on the local network. Depending on the
application, it is not necessary to provide such a device; if multiple A68/A38 (and/or
Teledyne Genie Nano-GigE) cameras are present in a subnet, automatically one of the
cameras will be selected to be the clock source for the other cameras.
When using an external PTP grandmaster clock, please make sure that its PTP Sync
Rate respects the IEEE 1588-2008 standard, that is, no higher than 10 Sync messages
per second. Some PTP grandmaster clocks are configured by default to provide 128
Sync messages per second which is higher than what the A68/A38 can sustain. For
reference, when a A68/A38 camera operates as a PTP clock source, it sends out one
Sync message per second and this is sufficient to provide precision within a few
microseconds.

PTP Configuration Features

Features are available to configure PTP behavior and compensate for network
topologies that include standard Ethernet switches (without PTP transparent mode
support) which can introduce large, non-deterministic variations in the reception of PTP
packets. These features provide more tolerance to variations in network transmission
time of PTP packets.
Outlier Detection
When the camera receives a PTP sync messages from the master, if the difference in
timestamps (Master to Slave difference) is outside acceptable limits
(ptpServoStepThreshold), it is flagged as an "outlier" and ignored.
If the camera receives a large number of outliers, it is assumed that an event has
occurred on the ethernet network that makes it temporarily too unstable for the PTP
algorithm to run. In this case, the A68/A38 reverts its clock speed to its normal, non-
adjusted value and restarts acquiring statistics on the PTP master, that is, it enters the
synchronization state.
The ptpSyncHistorySize feature determines the number of PTP sync messages saved,
both valid and outlier; if the number of valid PTP sync in the history falls below the
minimum number of valid PTP sync messages (ptpSyncMinCount) required, the camera
reverts back to the Synchronizing state.
To reduce the impact of large adjustments that are still within the outlier threshold, a
user-configurable fraction of the timestamp difference (ptpClockOffsetAdjustFactor and
ptpClockSpeedAdjustFactor) can be used to perform the slave clock offset and speed
corrections. In addition, an upper limit to the size of the corrections can be applied
(ptpClockOffsetMaxAdjust and ptpClockSpeedMaxAdjust).

Related GigE Vision Features

PTP-related features are part of the Event Control feature category; for complete
feature descriptions refer to the Event Control Feature Descriptions.
86 • Features and Configuration Options FLIR A68/A38 Series IR Camera User's Manual