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) 
00067         {
00068              _ticker.attach_us(this, &DebounceIn::_callback, i); 
00069              //ticker.attach(callback(this, &Sonar::background_read), 0.01f)
00070              }
00071         
00072         /** set_samples
00073          *
00074          * Defines the number of samples before switching the shadow 
00075          * definition of the pin. 
00076          *
00077          * @param int i The number of samples.
00078          */        
00079         void set_samples(int i) { _samples = i; }
00080         
00081         /** read
00082          *
00083          * Read the value of the debounced pin.
00084          */
00085         int read(void) { return _shadow; }
00086         int trig(void) { _trig2 = _trig; _trig = 0; return _trig2; }
00087         int ntrig(void) { _ntrig2 = _ntrig; _ntrig = 0; return _ntrig2; }
00088         
00089 #ifdef MBED_OPERATORS
00090         /** operator int()
00091          *
00092          * Read the value of the debounced pin.
00093          */
00094         operator int() { return read(); }
00095 #endif  
00096 
00097         /** Constructor
00098          * 
00099          * @param PinName pin The pin to assign as an input.
00100          */
00101         DebounceIn(PinName pin) : DigitalIn(pin,PullUp) { _counter = 0; _samples = 5; set_debounce_us(8100); };
00102         
00103     protected:
00104         void _callback(void) { 
00105             if (DigitalIn::read()) { 
00106                 if (_counter < _samples) _counter++; 
00107                 if (_counter == _samples) 
00108                                     {
00109                                         _ntrig = 0; // comment if you don`t want to miss signal
00110                                         _nlock = 0;
00111                                         _shadow = 1;
00112                                         if (!_lock) {_trig = 1; _lock = 1;}
00113                                     } 
00114             }
00115             else { 
00116                 if (_counter > 0) _counter--; 
00117                 if (_counter == 0) 
00118                                     {
00119                                         _shadow = 0;
00120                                         _trig = 0; // comment if you don`t want to miss signal
00121                                         _lock = 0;
00122                                         if (!_nlock) {_ntrig = 1; _nlock = 1;}
00123                                     } 
00124             }
00125         }
00126         
00127         Ticker _ticker;
00128                 int    _lock;
00129                 int    _nlock;
00130                 
00131                 int    _ntrig;
00132                 int    _ntrig2;
00133                 
00134             int    _trig;
00135                 int    _trig2;
00136                 
00137                 int    _shadow;
00138         int    _counter;
00139         int    _samples;
00140 };
00141  
00142 #endif
00143