Encoder.h

00001 #ifndef ENCODER_H_INCLUDED
00002 #define ENCODER_H_INCLUDED
00003 
00004 /** Class to handle a rotary encoder
00005  *  The lib is interrupt based, therefore no update functions have to be called.
00006  *  Example usage:
00007  *  @code
00008  *
00009  *  #include "mbed.h"
00010  *  #include "Encoder.h"
00011  *
00012  *  RotaryEncoder encoder(D3, D4);
00013  *
00014  *  int main()
00015  *  {
00016  *      while(1)
00017  *      {
00018  *          int pos = encoder.position();
00019  *          wait(1.0f);
00020  *      }
00021  *  }
00022  *  @endcode
00023  */
00024 class RotaryEncoder {
00025 public:
00026     RotaryEncoder(PinName outa, PinName outb)
00027         : position_(0), delta_(0),
00028           inta_(outa), intb_(outb), outa_(outa), outb_(outb) {
00029         outa_.mode(PullUp);
00030         outb_.mode(PullUp);
00031         inta_.rise(this, &RotaryEncoder::handleIntA);
00032         inta_.fall(this, &RotaryEncoder::handleIntA);
00033         intb_.rise(this, &RotaryEncoder::handleIntB);
00034         intb_.fall(this, &RotaryEncoder::handleIntB);
00035     }
00036 
00037     /** Returns the overall position of the encoder
00038      */
00039     int position() {
00040         return position_;
00041     }
00042 
00043     /** Returns the encoders change since the last call to this function
00044      */
00045     int delta() {
00046         int d = delta_;
00047         delta_ = 0;
00048         return d;
00049     }
00050 
00051 private:
00052 
00053     // A  = B --> Clockwise
00054     // A /= B --> Counter clockwise
00055     void handleIntA() {
00056         if (outa_ == outb_) {
00057             increment(1);
00058         } else {
00059             increment(-1);
00060         }
00061     }
00062 
00063     // A  = B --> Counter clockwise
00064     // A /= B --> Clockwise
00065     void handleIntB() {
00066         if (outa_ == outb_) {
00067             increment(-1);
00068         } else {
00069             increment(1);
00070         }
00071     }
00072 
00073     void increment(int i) {
00074         position_ += i;
00075         delta_ += i;
00076     }
00077 
00078     int position_;
00079     int delta_;
00080 
00081     InterruptIn inta_;
00082     InterruptIn intb_;
00083     DigitalIn outa_;
00084     DigitalIn outb_;
00085 };
00086 
00087 #endif /* ENCODER_H_INCLUDED */