Debounce a mechanical switch by periodic sampling.
Dependents: RedButton WS_7_Seg_mit_LM1635 WS_7_Seg_mit_LM1635 Lichtschalter_M0 ... more
Debouncer.cpp
- Committer:
- huliyang
- Date:
- 2015-05-18
- Revision:
- 0:2359961af424
- Child:
- 1:e59480cf6c72
File content as of revision 0:2359961af424:
/* Copyright (c) 2015 Liyang HU, MIT License * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ #include <mbed.h> #include <Debouncer.h> /*! \class Debouncer * \brief Debounce a mechanical switch by periodic sampling. * \code FIXME: EXAMPLE HERE * \endcode * \note This implements \a DebounceSwitch2() as described by * http://www.ganssle.com/debouncing-pt2.htm * \note In particular, directly hooking up a mechanical switch as an * interrupt will not suffice: in general, the signal will not always * satisfy any arbitrary processor's interrupt pin's min clock width, * data setup nor hold times & c., and will not trigger reliably. */ void Debouncer::tick(void) { previous = (previous << 1) | in; uint32_t rise = (1 << _samples) - 1; uint32_t window = rise + rise + 1; uint32_t recent = previous & window; if(recent == rise) { if(!now) fun_rise.call(); now = true; } else if(recent == (window & ~rise)) { if(now) fun_fall.call(); now = false; } } //! Create a \a Debouncer attached to the specified \a pin. //! \param pin Pin to poll. //! \param mode Pin mode, e.g. \a PullUp or \a PullDown. Debouncer::Debouncer(PinName pin, PinMode mode) : in(pin, mode), now(mode == PullUp), previous(mode == PullUp ? -1 : 0) { samples(); period(); } //! Set the number of identical samples needed to regard the input as stable. //! \note Limited to at most 32 samples. Debouncer &Debouncer::samples(int n) { _samples = n; return *this; } //! Set the time period between samples. Debouncer &Debouncer::period(float seconds) { detach(); attach(this, &Debouncer::tick, seconds); return *this; } //! Get the current stable state of the input. Debouncer::operator bool(void) { return now; } //! Attach a function to call when the stable state falls. Debouncer &Debouncer::attach_fall(void (*fun)(void)) { fun_fall.attach(fun); return *this; } //! Attach a function to call when the stable state rises. Debouncer &Debouncer::attach_rise(void (*fun)(void)) { fun_rise.attach(fun); return *this; } //! Attach a member function to call when the stable state falls. template <typename T> Debouncer &Debouncer::attach_fall(T *obj, void (T::*fun)(void)) { fun_fall.attach(obj, fun); return *this; } //! Attach a member function to call when the stable state rises. template <typename T> Debouncer &Debouncer::attach_rise(T *obj, void (T::*fun)(void)) { fun_rise.attach(obj, fun); return *this; }