vssp_capture_en

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Capture measurement data

This is an explanation of the command to caputure measurement data from Hokuyo 3D-LiDAR.
Use "DAT" command to start/stop capturing continuous measurement data.

Request

There are three types of measurement data that can be obtained with the "DAT" command,
and which type of the data is obtained is specified by the request command.

ri：range and intensity
ro：range only
ax：auxiliary sensor data

（ex.）capture of distance and intensity continuous
Start capture request command：　"DAT:ri=1\n"
Stop capture request command：　"DAT:ri=0\n"

Response

When the sensor receives the continuous capture start request command,
it sends the measurement data in continuous acquisition format.
The format of the response command is explained below using the ri command (distance + intensity) as an example.

The response includes "common header of VSSP", "measurement data header", "echo index array" and "measurement data array".
Only for the first time, VSSP common header and echo back is sent.

Note that all but the echo back and status are binary data, and all multi-byte data are little endian.

After the echo index array, the distance [mm] (2 bytes) intensity (2 bytes) are arranged for the total number of echoes.

【ex.】

line number　line = 2
Starting spot’s number　spot = 0
Echo index array　index[] = ｛0, 1, 3, 3, 5, …｝
Distance and intensity measurement data array　data[] = ｛100, 30, 150, 20, 105, 35, 102, 22, 103, 31, 111, 27, …｝

【Optional spot data capture procedure】

〇 echo count of spot data "i"th.

index[ i + 1 ] - index[ i ]

If the echo index overlaps with the previous value, the spot will be echoless. (Spot number 3 in the data example)

〇 access all echo data of optional spot

for (p = index[ i ], echo=0; p <= index[ i + 1 ]; ++p, ++echo){
// distance data[p * 2]
// intensity data[p * 2 + 1]
}