A
G
E
H
D
L
-
64
E
S2
and
S2.1
U
s
e
r
’
s
Ma nua
l
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 t
determine the point’s location in 3D space referred to by the return. Intensity and distance offsets must also be applied. Each sensor come
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.
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.
ou 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
senso
data later. The sensor has the capability to synchronize its data with GPS precision time. For more in this capability, see page 11.
Change
R
u
n
-
T
i
m
e
P
a
r
a
m
e
t
e
r
s
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
ll serial commands, except one version of the spin rate
command,
store
data
in
the
sensor’s
flash
memor
. 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
b
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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