.TH DEBOUNCE "9" "2007-01-16" "LinuxCNC Documentation" "HAL Component"

.SH NAME

debounce \- filter noisy digital inputs
.SH SYNOPSIS
.B loadrt debounce cfg=\fIsize[,size,...]\fB
.P
Creates debounce groups with the number of filters specified by (\fIsize\fR).
Every filter in the same group has the same sample rate and delay. For example
cfg=2,3 creates two filter groups with 2 filters in the first group and 3
filters in the second group.

.SH NOTE
.P
An alternate component named \fBdbounce\fR implements similar
functionality using conventional count= and names= parameters.  Delay
settings are implemented by a delay pin for each instance instead of
using filter groups.

.SH DESCRIPTION
The debounce filter works by incrementing a counter whenever the input is true,
and decrementing the counter when it is false.  If the counter decrements to
zero, the output is set false and the counter ignores further decrements.  If
the counter increments up to a threshold, the output is set true and the
counter ignores further increments.  If the counter is between zero and the
threshold, the output retains its previous state.  The threshold determines the
amount of filtering: a threshold of 1 does no filtering at all, and a threshold
of N requires a signal to be present for N samples before the output changes
state.  

.SH FUNCTIONS
.TP
.B debounce.\fIG\fR
Sample all the input pins in group G and update the output pins.
.SH PINS
.TP
.B debounce.\fIG\fB.\fIF\fB.in\fR bit in
The F'th input pin in group G.  
.TP
.B debounce.\fIG\fB.\fIF\fB.out\fR bit out
The F'th output pin in group G.  Reflects the last "stable" input seen on the
corresponding input pin.
.TP
.B debounce.\fIG\fB.delay\fR signed rw
Sets the amount of filtering for all pins in group G.