IWR1443: What is the unit of x=-209,y=637 in the picture? How to convert into meters?

user5144327

Intellectual 570 points

Part Number: IWR1443

Hello，please，What is the unit of x=-209,y=637 in the picture? How to convert into meters?

over 7 years ago

0 Wesley He over 7 years ago

TI__Expert 6205 points

Hi,

This is the define of the X,Y,Z.

typedef volatile struct MmwDemo_detectedObj_t
{
    uint16_t   rangeIdx;     /*!< @brief Range index */
    int16_t   dopplerIdx;   /*!< @brief Doppler index. Note that it is changed
                                 to signed integer in order to handle extended maximum velocity.
                                 Neagative values correspond to the object moving toward
                                 sensor, and positive values correspond to the
                                 object moving away from the sensor */
    uint16_t  peakVal;      /*!< @brief Peak value */
    int16_t  x;             /*!< @brief x - coordinate in meters. Q format depends on the range resolution */
    int16_t  y;             /*!< @brief y - coordinate in meters. Q format depends on the range resolution */
    int16_t  z;             /*!< @brief z - coordinate in meters. Q format depends on the range resolution */
} MmwDemo_detectedObj;

To convert it to meters, you can refer to this thread:

Thanks.

Regards,

Wesley

0 user5144327 over 7 years ago in reply to Wesley He

Intellectual 570 points

Hi Wesley,

Q format depends on the range resolution. After the experiment, I found that when the range resolution is 0.04, X/Y/Z is expressed in Q9 format; when the range resolution is 0.3, X/Y/Z is expressed in Q7 format; when the range resolution is 0.977, X/Y/Z is expressed in Q5 format. So what is the relationship between Q format and range resolution? Is there any law?

Thanks~

0 Luke Lin over 7 years ago in reply to user5144327

TI__Expert 3250 points

Hi,

The converting formula is as follows

xyzOutputQFormat = (uint32_t) ceil(log10(16./fabs(rangeResolution))/log10(2));

A table below for your convenience to refer.

rangeResolution>=16.0000000000, xyzOutputQFormat=0
rangeResolution>=8.0000000000, xyzOutputQFormat=1
rangeResolution>=4.0000000000, xyzOutputQFormat=2
rangeResolution>=2.0000000000, xyzOutputQFormat=3
rangeResolution>=1.0000000000, xyzOutputQFormat=4
rangeResolution>=0.5000000000, xyzOutputQFormat=5
rangeResolution>=0.2500000000, xyzOutputQFormat=6
rangeResolution>=0.1250000000, xyzOutputQFormat=7
rangeResolution>=0.0625000000, xyzOutputQFormat=8
rangeResolution>=0.0312500000, xyzOutputQFormat=9
rangeResolution>=0.0156250000, xyzOutputQFormat=10
rangeResolution>=0.0078125000, xyzOutputQFormat=11
rangeResolution>=0.0039062500, xyzOutputQFormat=12
rangeResolution>=0.0019531250, xyzOutputQFormat=13
rangeResolution>=0.0009765625, xyzOutputQFormat=14
rangeResolution>=0.0004882813, xyzOutputQFormat=15
rangeResolution>=0.0002441406, xyzOutputQFormat=16
rangeResolution>=0.0001220703, xyzOutputQFormat=17
rangeResolution>=0.0000610352, xyzOutputQFormat=18
rangeResolution>=0.0000305176, xyzOutputQFormat=19
rangeResolution>=0.0000152588, xyzOutputQFormat=20
rangeResolution>=0.0000076294, xyzOutputQFormat=21
rangeResolution>=0.0000038147, xyzOutputQFormat=22
rangeResolution>=0.0000019073, xyzOutputQFormat=23
rangeResolution>=0.0000009537, xyzOutputQFormat=24
rangeResolution>=0.0000004768, xyzOutputQFormat=25
rangeResolution>=0.0000002384, xyzOutputQFormat=26
rangeResolution>=0.0000001192, xyzOutputQFormat=27
rangeResolution>=0.0000000596, xyzOutputQFormat=28
rangeResolution>=0.0000000298, xyzOutputQFormat=29
rangeResolution>=0.0000000149, xyzOutputQFormat=30

The formula is located in C:\ti\mmwave_sdk_01_01_00_02\packages\ti\demo\xwr14xx\mmw\main.c

dataPathObj->xyzOutputQFormat = (uint32_t) ceil(log10(16./fabs(dataPathObj->rangeResolution))/log10(2));

You may also refer below posts for the detail

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IWR1443: What is the unit of x=-209,y=637 in the picture? How to convert into meters?