DebouncedIn.cpp

00001 /*
00002  * DebouncedIn class version 1.0
00003  * Created by Andres Moya Bedoya, updated by Ben Faucher
00004  */
00005 
00006 #include "DebouncedIn.h"
00007 #include "mbed.h"
00008 
00009 DebouncedIn::DebouncedIn(PinName in) 
00010     : _in(in) {    
00011         
00012     // Reset all the flags and counters    
00013     _samples = 0;
00014     _output = 0;
00015     _output_last = 0;
00016     _rising_flag = 0;
00017     _falling_flag = 0;
00018     _state_counter = 0;
00019     
00020     // Attach ticker
00021     _ticker.attach(this, &DebouncedIn::_sample, 0.005);     
00022 }
00023 
00024 DebouncedIn::DebouncedIn(PinName in, PinMode mode) 
00025     : _in(in, mode) {    
00026         
00027     // Reset all the flags and counters    
00028     _samples = 0;
00029     _output = 0;
00030     _output_last = 0;
00031     _rising_flag = 0;
00032     _falling_flag = 0;
00033     _state_counter = 0;
00034     
00035     // Attach ticker
00036     _ticker.attach(this, &DebouncedIn::_sample, 0.005);     
00037 }
00038 
00039 // Public member functions
00040 
00041 int DebouncedIn::read(void) {
00042     return(_output);
00043 }
00044 
00045 DebouncedIn::operator int() {
00046     return read();
00047 }
00048  
00049 // return number of rising edges
00050 int DebouncedIn::rising(void) {
00051     int return_value = _rising_flag; 
00052     _rising_flag = 0;
00053     return(return_value);
00054 }
00055  
00056 // return number of falling edges
00057 int DebouncedIn::falling(void) {
00058     int return_value = _falling_flag; 
00059     _falling_flag = 0;
00060     return(return_value);
00061 }
00062  
00063 // return number of ticks we've bene steady for
00064 int DebouncedIn::steady(void) {
00065 return(_state_counter);
00066 }
00067 
00068 // Private member functions
00069 void DebouncedIn::_sample() {
00070  
00071     // take a sample
00072     _samples = _samples >> 1; // shift right 1 bit
00073       
00074     if (_in) {
00075         _samples |= 0x80;
00076     }  
00077       
00078     // examine the sample window, look for steady state
00079     if (_samples == 0x00) {
00080         _output = 0;
00081     } 
00082     else if (_samples == 0xFF) {
00083         _output = 1;
00084     }
00085  
00086  
00087     // Rising edge detection
00088     if ((_output == 1) && (_output_last == 0)) {
00089         _rising_flag++;
00090         _state_counter = 0;
00091     }
00092  
00093     // Falling edge detection
00094     else if ((_output == 0) && (_output_last == 1)) {
00095         _falling_flag++;
00096         _state_counter = 0;
00097     }
00098     
00099     // steady state
00100     else {
00101         _state_counter++;
00102     }
00103     
00104    // update the output
00105     _output_last = _output;
00106     
00107 }