Velodyne Acoustics HDL-64E S2 - Manual (Page 11)

3. Parse the packets for rotation, block, distance and intensity data. Each sensor’s LIFO data packet has a 1206 byte payload consisting
of 12 blocks of 100 byte firing data followed by 6 bytes of calibration and other information pertaining to the sensor.
Each 100 byte record contains a block identifier, then a rotational value followed by 32 3-byte combinations that report on each laser fired
for the block. Two bytes report distance to the nearest 0.2 cm, and the remaining byte reports intensity on a scale of 0 -255. 12 100 byte
records exist, therefore, 6 records exist for each block in each packet. For more on packet construction, see Appendix E.
4. Apply the calibration factors to the data. Each of the sensor’s lasers is fixed with respect to vertical angle and offset to the rotational
index data provided in each packet. For each data point issued by the sensor, rotational and horizontal correction factors must be applied to
determine the point’s location in 3D space referred to by the return. Intensity and distance offsets must also be applied. Each sensor comes
from Velodyne’s factory calibrated using a dual-point calibration methodology, explained further in Appendix F.
The minimum return distance for the sensor is approximately 3 feet (0.9 meters). Ignore returns closer than this.
A file on the CD called “HDL Source Example” shows the calculations using the above correction factors. This DSR uses this code to
determine 3D locations of sensor data points.
5. Plot or store the data as needed. For DSR, the point-cloud data, once determined, is plotted onscreen. The source to do this can be
found on the CD and is entitled “HDL Plotting Example.” DSR uses OpenGL to do its plotting.
You may also want to store the data. If so, it may be useful to timestamp the data so it can be referenced and coordinated with other sensor
data later. The sensor has the capability to synchronize its data with GPS precision time. For more in this capability, see page 11.
Change Run-Time Parameters
The sensor has several run-time parameters that can be changed using the RS-232 serial port. For all commands, use the following
serial parameters:
• Baud 9600
• Parity: None
• Data bits: 8
• Stop bits: 1
All serial commands, except one version of the spin rate command, store data in the sensor’s flash memory. Data stored in flash memory
through serial commands is retained during firmware updates or power cycles.
The sensor has no echo back feature, so no serial data is returned from the sensor. Commands can be sent using a terminal program or by
using batch files (e.g. .bat). A sample .bat file is shown below.
Sample Batch File (.bat)
MODE COM3: 9600,N,8,1 COPY SERCMD.txt COM3 Pause
Sample SERCMD.txt file
This command sets the spin rate to 300 RPM and stores the new value in the unit’s flash memory.
#HDLRPM0300$
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HDL-64E S2 and S2.1 User’s Manual
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