IWR6843ISK: doppler value in point cloud data

Takatoshi Tsuji

Part Number: IWR6843ISK

Hello ,

I am testing IWR6843ISK by "Sense and HAVC control" demo.

It seems doppler value in point cloud data is zero or plus but is not minus. But doppler value by demo visualizer is indicated from plus to minus.

I am fine if doppler value in point cloud data can be indicated from plus to minus as demo visualizer.

Best regards,

Taka

over 5 years ago

0 Justin Curewitz over 5 years ago

TI__Mastermind 28055 points

Hi Taka,

I will test to see if I can reproduce this. Before I do, are you using the pointUnit value to decompress the point cloud data?

Regards,

Justin

0 Takatoshi Tsuji over 5 years ago in reply to Justin Curewitz

Expert 1550 points

Hello Justin,

Probably yes. Actually we are reading 'dopplerUnit' in pointCloudUnitStruct as shown in P4 in attached document.

Best regards,

sense_and_direct_68xx_data_output_format.pdfTaka

0 Justin Curewitz over 5 years ago in reply to Takatoshi Tsuji

TI__Mastermind 28055 points

Hi Taka,

The dopplerUnit should be read. Then for each point, the doppler value needs to be multiplied by the doppler unit to get the true doppler value.

When you get the point cloud TLV, you will have one Unit Struct, then you will have the point cloud data.

Regards,

Justin

0 Takatoshi Tsuji over 5 years ago in reply to Justin Curewitz

Expert 1550 points

Hello Justin,

Yes, we are reading pointUnit x doppler and it seems the polarity is always plus by 'Sense and Direct HVAC Control' demo.

But in case of 3D people counting, doppler value has both polarity....

Please kindly share dopper value that you got in your environment.

Best regadrs,

Taka

0 Takatoshi Tsuji over 5 years ago in reply to Takatoshi Tsuji

Expert 1550 points

doppler.pdfHello Justin,

Let me share our findings in attached file. It seems doppler value from 3D people counting demo has different spec to Sense and Direct HVAC control demo.

Please kindly confirm.

Best regards,

Taka

0 Takatoshi Tsuji over 5 years ago in reply to Takatoshi Tsuji

Expert 1550 points

Hello Justin,

Could you kindly answer to previous my question ?

Best regards,

Taka

0 Justin Curewitz over 5 years ago in reply to Takatoshi Tsuji

TI__Mastermind 28055 points

Hi Taka,

There is a bug in the parsing software. When the point cloud data is parsed, first we get the pointUnit struct, which is 4 floats - these values are used to decompress point cloud info. From the pointUnit struct, we get the dopplerUnit, which is a float, in default config is about 0.0935. Then for each point, we will get a doppler value as a unit8_t value. This value needs to be transformed using the following formula:

if (doppler >= 128):

doppler = doppler - 256

doppler = doppler x dopplerUnit.

The script was missing the first step, where 256 is subtracted from values greater than 128, so all values came out as positive.

This can be fixed by adding the following lines to the oob_parser.py script:

if (doppler >= 128):
doppler -= 256

I added this in the function "parseDetectedObjectsIFDM" at line 141, but line numbers may be different for you. It needs to come inside the "Try" loop, before:

self.pcPolar[2,i] = doppler*pUnit[1] #doppler

Regards,

Justin

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IWR6843ISK: doppler value in point cloud data