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component lowpass "Low-pass filter";
notes """
\\fBgain\\fR pin setting
The digital filter implemented is equivalent to a unity-gain
continuous-time single-pole low-pass filter that is preceded
by a zero-order-hold and sampled at a fixed period. For a pole
at \\fB-a\\fR (radians/seconds) the corresponding continuous-time
lowpass filter LaPlace transfer function is:
\\fBH(s) = a/(s + a)\\fR
For a sampling period \\fBT\\fR (seconds), the gain for this
Hal lowpass component is:
\\fBgain = 1 - e^(-a * T)\\fR
e = 2.71828 https://en.wikipedia.org/wiki/E_(mathematical_constant)
\\fBExamples:\\fR
T = 0.001 seconds (typical servo thread period)
a = (2*pi*100) (\\fB100Hz\\fR bandwidth single pole)
gain = \\fB0.466\\fR
T = 0.001 seconds (typical servo thread period)
a = (2*pi*10) ( \\fB10Hz\\fR bandwidth single pole)
gain = \\fB0.0609\\fR
T = 0.001 seconds (typical servo thread period)
a = (2*pi*1) ( \\fB1Hz\\fR bandwidth single pole)
gain = \\fB0.0063\\fR
""";
pin in float in;
pin out float out " out += (in - out) * gain ";
pin in bit load "When TRUE, copy \\fBin\\fR to \\fBout\\fR instead of applying the filter equation.";
param rw float gain;
function _;
license "GPL";
author "Jeff Epler";
notes "The effect of a specific \\fBgain\\fR value is dependent on the period of the function that \\fBlowpass.\\fIN\\fR is added to.";
;;
FUNCTION(_) {
if(load)
out = in;
else
out += (in - out) * gain;
}
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