Velodyne Acoustics HDL-64E S2.1 user manual APPendix G ethernet transit tiMinG taBLe

aPPendix G: ethernet transit tiMinG taBLe

HDL-64E S2 and S2.1 User’s Manual

HDL-64E Ethernet Timing Table Overview

The Ethernet Timing Table shows how much time elapses between the actual capturing of a point’s data event and when that point is an event output from the sensor. By registering the event of the Ethernet data capture, you can calculate back in time the exact time at which any particular distance point was captured. The formula is as follows:

Actual Event Timestamp = (Data Packet Event Output Timestamp) – (Timing Table Event Timestamp)

The upper block and lower block collect distance points simultaneously with each block issuing single laser pulses at a time. That is, each upper block laser fires in sequence and in unison to a corresponding laser from the lower block.

For example, laser 32 fires simultaneously with laser 0, laser 33 fires with laser 1, and so on.

The sensor has an equal number of upper and lower block returns. This is why when interpreting the delay table each sequential pair of data blocks represents the upper and lower block respectively, and each upper and lower block pair of data blocks in the Ethernet packet has the same delay value.

Ethernet packets are assembled until the entire 1200 bytes have been collected, representing six upper block sequences and six lower block sequences. The packet is then transmitted via a UDP packet over Ethernet, starting from the last byte acquired. See a sample of the packet format in Appendix E.

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