Linux/AWR1642BOOST: ROS package msg data format

Gelei Deng

Part Number: AWR1642BOOST
Other Parts Discussed in Thread: AWR1642

Tool/software: Linux

Hi,

I'm handling the AWR1642 ROS package. I tried to echo the data from publisher out, and I received the data in the following format:

header:
seq: 948
stamp:
    secs: 0
    nsecs:         0
frame_id: "base_radar_link"
height: 1
width: 71
fields:
-
    name: "x"
    offset: 0
    datatype: 7
    count: 1
-
    name: "y"
    offset: 4
    datatype: 7
    count: 1
-
    name: "z"
    offset: 8
    datatype: 7
    count: 1
-
    name: "intensity"
    offset: 16
    datatype: 7
    count: 1
is_bigendian: False
point_step: 32
row_step: 2272
data: [0, 0, 64, 60, 0, 0, 48, 61, 0, 0, 0, 0... (lots of data here)]

is_dense: True

I am wondering how the data is packed in the "data" list? Also, is there a way to get the position of objects easily?

Best regards.

Gelei

over 7 years ago

0 Nitin Sakhuja over 7 years ago

TI__Mastermind 30405 points

Hi Gelei,

Which message and publisher are you referring to? I need to do some investigation on this topic so please expect a response by Monday next week (02-Apr)

Thanks
-Nitin

0 Gelei Deng over 7 years ago in reply to Nitin Sakhuja

Prodigy 100 points

Hi Nitin,

I'm referring to the ROS msg /mmWaveDataHdl/RScan. I tried to echo this msg out and I don't quite understand how to read the "data" within. I can identify how many objects in each frame, and some other information, but I don't know how to read the data vector.

For instance:

---
header:
seq: 66963
stamp:
    secs: 0
    nsecs:         0
frame_id: "base_radar_link"
height: 1
width: 78
fields:
-
    name: "x"
    offset: 0
    datatype: 7
    count: 1
-
    name: "y"
    offset: 4
    datatype: 7
    count: 1
-
    name: "z"
    offset: 8
    datatype: 7
    count: 1
-
    name: "intensity"
    offset: 16
    datatype: 7
    count: 1
is_bigendian: False
point_step: 32
row_step: 2496
data: [0, 0, 0, 61, 0, 0, 0, 61, 0, 0, 0, 0, 0, 0, 128, 63, 157, 246, 5, 66, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 120, 61, 0, 0, 128, 61, 0, 0, 0, 0, 0, 0, 128, 63, 182, 80, 10, 66, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 188, 61, 0, 0, 192, 61, 0, 0, 0, 0, 0, 0, 128, 63, 170, 222, 1, 66, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 46, 62, 0, 0, 32, 61, 0, 0, 0, 0, 0, 0, 128, 63........]
is_dense: True
---
I know there are 78 objects detected in this frame, but may I know how to read the x, y, z of each point from the data?

Best regards,

Gelei

0 Nitin Sakhuja over 7 years ago in reply to Gelei Deng

TI__Mastermind 30405 points

Hi Gelei,

Sorry for the delay. ROS defines the PointCloud2 message as given on ROS wiki at wiki.ros.org/.../Overview.

The PointCloud2 message encapsulates the core PointCloud data type for the point object as defined in the point cloud library (PCL). More information on this data type is available here:

pointclouds.org/.../adding_custom_ptype.php.

PCL defines various pre-defined point types as given on this page e.g. PointXYZ, PointXYZI, PointXYZRGB etc. The particular one being used in the mmWave ROS driver is PointXYZI (X, Y, Z and Intensity)

The Point information which consists of X, Y, Z and Intensity is being populated in the RScan message in the folling file:

~/catkin_ws/src/ti_mmwave_rospkg/src/DataHandlerClass.cpp, Method: DataUARTHandler::sortIncomingData (look under case READ_OBJ_STRUCT).

The information about the field name and data type is provided in the message header e.g.:

name: "x"
offset: 0
datatype: 7
count: 1
-

datatype 7 represents Float32 as given here: docs.ros.org/.../PointField.html.

So the data array consists of structures of XYZI values.

Regards
-Nitin

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Linux/AWR1642BOOST: ROS package msg data format