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<?php

function doit_rssi($txPower,$rssi)

{

$refDistance = 1.0;

$pathLoss = 3.2;

$c1=$txPower;

$c2=$pathLoss;

$fm=($c1-$rssi)/(10*$c2);

echo "fm".$fm."\r\n";

$fp=pow(10,$fm);

$ret=$refDistance*$fp/100;

return $ret;

}

function doit_to_rssi($txPower,$distance)

{

$refDistance = 1.0;

$pathLoss = 3.5;

$c1=$txPower;

$c2=$pathLoss;

$distanceDiff = $distance*100 / $refDistance;

$ret=$c1 - 10 * $c2 * log10($distanceDiff);

return $ret;

}

//$tx=19.5;

$tx=21;

$rssi=-41;

echo "txPower=$tx \r\n";

$ret=doit_rssi($tx,$rssi);

echo $ret."\r\n";

echo "Distance"."     "."    RSSI"."\r\n";

for($i=2;$i<=10;$i++){

$rssi=(-1)*$i*10;

$ret=doit_rssi($tx,$rssi);

echo $ret."          ".$rssi."\r\n";

}

return ;

echo $ret."\r\n";

echo "Distance"."     "."RSSI"."\r\n";

return;

for($i=1;$i<=10;$i++){

$d=$i*3;

$ret=doit_to_rssi($tx,$d);

echo $d."          ".$ret."\r\n";

}

?>

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