DebouncedIn.cpp

00001 #include "DebouncedIn.h"
00002 #include "mbed.h"
00003  
00004  /*
00005   * Constructor
00006   */
00007  DebouncedIn::DebouncedIn(PinName in) 
00008      : _in(in) {    
00009          
00010      // reset all the flags and counters    
00011      _samples = 0;
00012      _output = 0;
00013      _output_last = 0;
00014      _rising_flag = 0;
00015      _falling_flag = 0;
00016      _state_counter = 0;
00017      
00018      // Attach ticker
00019      _ticker.attach(this, &DebouncedIn::_sample, 0.005);     
00020  }
00021    
00022  void DebouncedIn::_sample() {
00023  
00024      // take a sample
00025      _samples = _samples >> 1; // shift left
00026        
00027      if (_in) {
00028          _samples |= 0x80;
00029      }  
00030        
00031      // examine the sample window, look for steady state
00032      if (_samples == 0x00) {
00033          _output = 0;
00034      } 
00035      else if (_samples == 0xFF) {
00036          _output = 1;
00037      }
00038  
00039  
00040      // Rising edge detection
00041      if ((_output == 1) && (_output_last == 0)) {
00042          _rising_flag++;
00043          _state_counter = 0;
00044      }
00045  
00046      // Falling edge detection
00047      else if ((_output == 0) && (_output_last == 1)) {
00048          _falling_flag++;
00049          _state_counter = 0;
00050      }
00051      
00052      // steady state
00053      else {
00054          _state_counter++;
00055      }
00056      
00057     // update the output
00058      _output_last = _output;
00059      
00060  }
00061  
00062  
00063  
00064  // return number of rising edges
00065  int DebouncedIn::rising(void) {
00066      int return_value = _rising_flag; 
00067      _rising_flag = 0;
00068      return(return_value);
00069  }
00070  
00071  // return number of falling edges
00072  int DebouncedIn::falling(void) {
00073      int return_value = _falling_flag; 
00074      _falling_flag = 0;
00075      return(return_value);
00076  }
00077  
00078  // return number of ticsk we've bene steady for
00079  int DebouncedIn::steady(void) {
00080  return(_state_counter);
00081  }
00082  
00083  // return the debounced status
00084  int DebouncedIn::read(void) {
00085      return(_output);
00086  }
00087  
00088  // shorthand for read()
00089  DebouncedIn::operator int() {
00090      return read();
00091  }