Other Parts Discussed in Thread: IWR6843
Hello everyone,
See, now that I managed to receive data from the IWR6843 radar, I have now a specific matter to tackle, in which I don't really have any idea on how to go about it..
Specifically, about the Azimuth heatmap data. According to your documentation, it is represented by an array of 32bit struct divided into a 16bit real integer and 16bit imaginary integer which has a width in virtual antennas (which was 8 in my case because of 4 receptors and 2 transceivers) and a height in Range FFT (which I deduced to be 256 because of Range Profile which was a multiple of Range FFT and 2bytes and received 512 bytes as data).
My question is, what do we interpret from those real and imaginary numbers in order to form a heatmap as shown in the demo. Because in the demo, we see the heatmap as a map with colours ranging from blue to red and passing by green, but what determines this colour scheme out of those integers we have at hand ?
Also I know that there is a code regarding this in the javascript, but I don't quite understand the steps that it goes through, like what kind of mathematical calculations are necessary to have the final data, and since I'm not that familiar with java and not that good in maths, I couldn't deduce what it does.
If anyone knows the mathematical equation to what is happening that would be great, it would even be greater if somebody had a C code version of the following code :
var processAzimuthHeatMap = function (bytevec, byteVecIdx, Params) {
var elapsed_time = {}; // for profile this code only
var subFrameNum = Params.currentSubFrameNumber;
if (subFrameNum != Params.subFrameToPlot) return;
if (Params.guiMonitor[subFrameNum].rangeAzimuthHeatMap == 1) {
var start_time = new Date().getTime();
// %Range complex bins at zero Doppler all virtual (azimuth) antennas
var numBytes = Params.dataPath[subFrameNum].numTxAzimAnt *
Params.dataPath[subFrameNum].numRxAnt *
Params.dataPath[subFrameNum].numRangeBins * 4;
var q = bytevec.slice(byteVecIdx, byteVecIdx + numBytes);
// q = q(1:2:end)+q(2:2:end)*2^8;
// q(q>32767) = q(q>32767) - 65536;
// q = q(1:2:end)+1j*q(2:2:end);
// ==> q[4*idx+1]q[4*idx+0] is real, q[4*idx+3]q[4*idx+2] is imag,
// q = reshape(q, Params.dataPath.numTxAzimAnt*Params.dataPath.numRxAnt, Params.dataPath.numRangeBins);
// Q = fft(q, NUM_ANGLE_BINS); % column based NUM_ANGLE_BINS-point fft, padded with zeros
// QQ=fftshift(abs(Q),1);
// QQ=QQ.';
var qrows = Params.dataPath[subFrameNum].numTxAzimAnt * Params.dataPath[subFrameNum].numRxAnt, qcols = Params.dataPath[subFrameNum].numRangeBins;
var qidx = 0;
var QQ = [];
for (var tmpc = 0; tmpc < qcols; tmpc++) {
var real = math.zeros(NUM_ANGLE_BINS).valueOf();
var imag = math.zeros(NUM_ANGLE_BINS).valueOf();
for (var tmpr = 0; tmpr < qrows; tmpr++) {
real[tmpr] = q[qidx + 1] * 256 + q[qidx];
if (real[tmpr] > 32767) real[tmpr] = real[tmpr] - 65536;
imag[tmpr] = q[qidx + 3] * 256 + q[qidx + 2];
if (imag[tmpr] > 32767) imag[tmpr] = imag[tmpr] - 65536;
qidx = qidx + 4;
}
fft.transform(real, imag);
for (var ri = 0; ri < NUM_ANGLE_BINS; ri++) {
real[ri] = Math.sqrt(real[ri] * real[ri] + imag[ri] * imag[ri]); // abs()
}
QQ.push(real.slice(NUM_ANGLE_BINS / 2).concat(real.slice(0, NUM_ANGLE_BINS / 2)));
}
// QQ=QQ(:,2:end);
// fliplr(QQ)
var fliplrQQ = [];
for (var tmpr = 0; tmpr < QQ.length; tmpr++) {
fliplrQQ.push(QQ[tmpr].slice(1).reverse());
}
var start_time2 = new Date().getTime();
if (Params.rangeAzimuthHeatMapGridInit == 0) {
// theta = asind([-NUM_ANGLE_BINS/2+1 : NUM_ANGLE_BINS/2-1]'*(2/NUM_ANGLE_BINS));
// range = [0:Params.dataPath.numRangeBins-1] * Params.dataPath.rangeIdxToMeters;
var theta = math.asin(math.dotMultiply(math.range(-NUM_ANGLE_BINS / 2 + 1, NUM_ANGLE_BINS / 2 - 1, true), 2 / NUM_ANGLE_BINS)).valueOf(); // in radian
var range = math.dotMultiply(math.range(0, Params.dataPath[subFrameNum].numRangeBins - 1, true), Params.dataPath[subFrameNum].rangeIdxToMeters).valueOf();
range = math.subtract(range, Params.compRxChanCfg.rangeBias); //correct regardless of state (measurement or compensation)
math.forEach(range, function (value, idx, ary) {
ary[idx] = math.max(ary[idx], 0);
});
// posX = range' * sind(theta');
// posY = range' * cosd(theta');
var posX = MyUtil.tensor(range, math.sin(theta));
var posY = MyUtil.tensor(range, math.cos(theta));
Params.rangeAzimuthHeatMapGrid_xlin = math.range(-range_width, range_width, 2.0 * range_width / (Params.rangeAzimuthHeatMapGrid_points - 1), true).valueOf();
if (Params.rangeAzimuthHeatMapGrid_xlin.length < Params.rangeAzimuthHeatMapGrid_points) Params.rangeAzimuthHeatMapGrid_xlin.push(range_width);
Params.rangeAzimuthHeatMapGrid_ylin = math.range(0, range_depth, 1.0 * range_depth / (Params.rangeAzimuthHeatMapGrid_points - 1), true).valueOf();
if (Params.rangeAzimuthHeatMapGrid_ylin.length < Params.rangeAzimuthHeatMapGrid_points) Params.rangeAzimuthHeatMapGrid_ylin.push(range_depth);
var xiyi = MyUtil.meshgrid(Params.rangeAzimuthHeatMapGrid_xlin, Params.rangeAzimuthHeatMapGrid_ylin);
Params.rangeAzimuthHeatMapGrid = new math_griddata();
Params.rangeAzimuthHeatMapGrid.init(math.flatten(posX), math.flatten(posY), xiyi[0], xiyi[1]);
Params.rangeAzimuthHeatMapGridInit = 1;
}
var zi = Params.rangeAzimuthHeatMapGrid.griddata_from_cache(math.flatten(fliplrQQ));
zi = MyUtil.reshape_rowbased(zi, Params.rangeAzimuthHeatMapGrid_ylin.length, Params.rangeAzimuthHeatMapGrid_xlin.length);
var start_time3 = new Date().getTime();
templateObj.$.ti_widget_plot4.data[0].x = Params.rangeAzimuthHeatMapGrid_xlin;
templateObj.$.ti_widget_plot4.data[0].y = Params.rangeAzimuthHeatMapGrid_ylin;
templateObj.$.ti_widget_plot4.data[0].z = zi;
plotredraw(templateObj.$.ti_widget_plot4);
elapsed_time.rangeAzimuthHeatMap = [start_time2 - start_time, start_time3 - start_time2, new Date().getTime() - start_time3];
}
};
I couldn't understand when the code began to initalise the QQ variable, because before was about capturing the data.
Best regards
Sebastien
Sebastien
