IWR6843ISK: 6843ISK

Hello Larry,

It is organized as shown below. So you will have 128 chirps per frame, then the 129th chirp you will see is the first chirp of the second frame.

Going to page 9 of this document below will give more details.

https://www.ti.com/lit/swra581

Best Regards,

Pedrhom

It doesn't seem like this is totally correct.  Here is why....I take the first 256 A/D samples from Rx0 of chirp 1, and compare it to the 256 A/D samples of Rx0 of chirp 2.  They graph almost on top of each other.  Very close.  Then I go to chirp 127, and plot the 256 A/D samples of Rx0 against chirp 128 of the 256 A/D samples of Rx0.  These again plot almost on top of each other.  Very close.  But then  I plot chirp 128 of the Rx0 256 samples against chirp 129 (which should be the first chirp of Frame 2) of the Rx0 256 A/D samples, they are not very close.  They do not plot nearly on top of each other.  What is different about this boundary when I thought it was just another sequential chirp.   Is there a long delay or something that would cause these consecutive chirp results on on the same Rx to not be similar?  

Thanks,

Larry

Hello Larry,

How long is the frame time? And were these measurements taken in a static, low noise scene?  In general, in a static environment, I would expect the data between frames to be close too as you say.  Could you post a picture of some sort or an example to help show the differences?  For example, if you can post the ADC data for chirp1, chirp2, chirp128, chirp129, chirp 130 and chirp 256. 

Best Regards,

Pedrhom

These were taken using a corner reflector at about 1 meter.  Low noise and static.  I will insert 4 plots I made.  

Hello,

I see what you mean, in addition chirp1 and chirp 127 are very different as well. This is not expected, so I will need more information

1. You are seeing this with 'real' data, are you also seeing this with 'complex'?

2. Could you please post your chirp configuration here?

3. Are you able to post your parsing script? Feel free to attach the script as is, I want to confirm there is nothing wrong with your equations for parsing.

Best Regards,

Pedrhom

Pedrhorn,

I was expecting 1 to 128 to be somewhat different, since I was holding a small corner reflector at about 1 meter.  I will have some movement.  I did see that difference.  

For now, I am just looking at real data.  Config screen shots:

%%mmWave1 is the name of this Octave file by LJK
% written 08/22/24

%%% This script is used to read the binary file produced by the DCA1000
%%% and Mmwave Studio
%%% Command to run in Matlab GUI -

%% global variables
% change based on sensor config
close all
filename = 'adc_data090624_3.bin';
addpath('C:/Users/LarryKoudele/Desktop/6843ISK');
%printf ("Filename is '%s'\n",filename);
printf ("Filename is '%s'\n",filename);

numADCSamples = 256; % number of ADC samples per chirp
numADCBits = 16; % number of ADC bits per sample
numRX = 4; % number of receivers
numLanes = 2; % do not change. number of lanes is always 2
isReal = 1; % set to 1 if real only data, 0 if complex data0
Numframes = 8;
numChirps = 128;
%% read file
% read .bin file
fid = fopen(filename,'r');
adcData = fread(fid,"int16"); %doesn't get back a int16?
% if 12 or 14 bits ADC per sample compensate for sign extension
adcData = int16(adcData);

if numADCBits ~= 16
l_max = 2^(numADCBits-1)-1;
adcData(adcData > l_max) = adcData(adcData > l_max) - 2^numADCBits;
end
fclose(fid);
fileSize = size(adcData, 1);
% real data reshape, filesize = numADCSamples*numChirps
if isReal
numChirps = fileSize/numADCSamples/numRX;
LVDS = zeros(1, fileSize);
%create column for each chirp
LVDS = reshape(adcData, numADCSamples*numRX, numChirps);
%each row is data from one chirp
LVDS = LVDS.'; %makes each row a column. Now, rows are the chirps.
else
% for complex data
% filesize = 2 * numADCSamples*numChirps
numChirps = fileSize/2/numADCSamples/numRX;
LVDS = zeros(1, fileSize/2);
%combine real and imaginary part into complex data
%read in file: 2I is followed by 2Q
counter = 1;
for i=1:4:fileSize-1
LVDS(1,counter) = adcData(i) + sqrt(-
1)*adcData(i+2); LVDS(1,counter+1) = adcData(i+1)+sqrt(-
1)*adcData(i+3); counter = counter + 2;
end
% create column for each chirp
LVDS = reshape(LVDS, numADCSamples*numRX, numChirps);
%each row is data from one chirp
LVDS = LVDS.';
end
%organize data per RX
adcData = zeros(numRX,numChirps*numADCSamples);
for row = 1:numRX
for i = 1: numChirps
%adcData(row, (i-1)*numADCSamples+1:i*numADCSamples) = LVDS(i,row*numADCSamples+1:row*numADCSamples); %this was wrong from TI
adcData(row, (i-1)*numADCSamples+1:i*numADCSamples) = LVDS(i,(row-1)*numADCSamples+1:row*numADCSamples); %this is correct now LJK
end
end
% return receiver data
retVal = adcData;

xmax = numADCSamples;
Rx = 1 %Read antenna Rx 1 to 4
RefChirp = 1;
RefData = adcData(Rx,(RefChirp-1)*xmax+1:RefChirp*xmax);
%numADCsamples = 256 typically
%ChirpNum = 1 to 1024
ChirpNum = 50;
%RefData = adcData(Rx,1:256);
xx = 1:xmax;
figure(Rx);
hold on
plot(xx,RefData);
axis([0 xmax min(adcData(Rx,:)) max(adcData(Rx,:))])
title("Radar Beat Freq")
xlabel("Sample Number")
ylabel("A/D values ")
grid on
xxx = adcData(Rx,(ChirpNum-1)*xmax+1:ChirpNum*xmax);
plot(xx,xxx);

Hello Larry,

This may be due to BPM being enabled, A + B will be OK but A-B will look like no detection. Do you see the same thing when setting MIMO to TDM instead?

Best Regards,

Pedrhom