DebounceIn.h

00001 /*
00002     Copyright (c) 2010 Andy Kirkham
00003  
00004     Permission is hereby granted, free of charge, to any person obtaining a copy
00005     of this software and associated documentation files (the "Software"), to deal
00006     in the Software without restriction, including without limitation the rights
00007     to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008     copies of the Software, and to permit persons to whom the Software is
00009     furnished to do so, subject to the following conditions:
00010  
00011     The above copyright notice and this permission notice shall be included in
00012     all copies or substantial portions of the Software.
00013  
00014     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017     AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018     LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019     OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00020     THE SOFTWARE.
00021 */
00022  
00023 #ifndef DEBOUNCEIN_H
00024 #define DEBOUNCEIN_H
00025  
00026 #include "mbed.h"
00027 
00028 /** DebounceIn adds mechanical switch debouncing to DigitialIn.
00029  *
00030  * Example:
00031  * @code
00032  * #include "mbed.h"
00033  * #include "DebounceIn.h"
00034  *
00035  * DebounceIn  d(p5);
00036  * DigitialOut led1(LED1);
00037  * DigitialOut led2(LED2);
00038  *
00039  * int main() {
00040  *     while(1) {
00041  *         led1 = d;
00042  *         led2 = d.read();
00043  *     }
00044  * }
00045  * @endcode
00046  *
00047  * @see set_debounce_us() To change the sampling frequency.
00048  * @see set_samples() To alter the number of samples.
00049  *
00050  * Users of this library may also be interested in PinDetect library:-
00051  * @see http://mbed.org/users/AjK/libraries/PinDetect/latest
00052  *
00053  * This example shows one input displayed by two outputs. The input
00054  * is debounced by the default 10ms.
00055  */
00056  
00057 class DebounceIn : public DigitalIn {
00058     public:
00059     
00060         /** set_debounce_us
00061          *
00062          * Sets the debounce sample period time in microseconds, default is 1000 (1ms)
00063          *
00064          * @param int i The debounce sample period time to set.
00065          */        
00066         void set_debounce_us(int i) { _ticker.attach_us(this, &DebounceIn::_callback, i); }
00067         
00068         /** set_samples
00069          *
00070          * Defines the number of samples before switching the shadow 
00071          * definition of the pin. 
00072          *
00073          * @param int i The number of samples.
00074          */        
00075         void set_samples(int i) { _samples = i; }
00076         
00077         /** read
00078          *
00079          * Read the value of the debounced pin.
00080          */
00081         int read(void) { return _shadow; }
00082         
00083 #ifdef MBED_OPERATORS
00084         /** operator int()
00085          *
00086          * Read the value of the debounced pin.
00087          */
00088         operator int() { return read(); }
00089 #endif  
00090 
00091         /** Constructor
00092          * 
00093          * @param PinName pin The pin to assign as an input.
00094          */
00095         DebounceIn(PinName pin) : DigitalIn(pin) { _counter = 0; _samples = 10; set_debounce_us(1000); };
00096         
00097     protected:
00098         void _callback(void) { 
00099             if (DigitalIn::read()) { 
00100                 if (_counter < _samples) _counter++; 
00101                 if (_counter == _samples) _shadow = 1; 
00102             }
00103             else { 
00104                 if (_counter > 0) _counter--; 
00105                 if (_counter == 0) _shadow = 0; 
00106             }
00107         }
00108         
00109         Ticker _ticker;
00110         int    _shadow;
00111         int    _counter;
00112         int    _samples;
00113 };
00114  
00115 #endif
00116