pulse_decoder.h

00001 #ifndef PULSE_DECODER_H
00002 #define PULSE_DECODER_H
00003 
00004 /// @file pulse_decoder.h This library provides a simple PWM decoder class.
00005 ///
00006 /// The approach is based on installing two interrupt routines for the rising and
00007 /// falling edges of an input pin and measuring the time between the two events.
00008 ///
00009 /// Example:
00010 /// @code
00011 /// #include "mbed.h"
00012 /// void main()
00013 /// {
00014 ///     pulse_decoder pulse(D7);
00015 ///
00016 ///     while(true) {
00017 ///         printf("Pulse high = %5d low = %5d (us) Period = %5d\n", 
00018 ///           pulse.get_high_period(), pulse.get_low_period(), 
00019 ///           pulse.get_high_period() + pulse.get_low_period());  
00020 ///         wait(.2);
00021 ///     }    
00022 /// }
00023 /// @endcode
00024 
00025 class pulse_decoder {
00026 public:
00027     ///Creates a pulse_decoder
00028     ///@param[in] pin the input pin on the microcontroller
00029     pulse_decoder(PinName pin);
00030     
00031     ///Get the period of time that the pulse was in high state
00032     ///@return the period in us
00033     int get_high_period() const
00034     {
00035         return high_period;
00036     }
00037 
00038     ///Get the period of time that the pulse was in low state
00039     ///@return the period in us        
00040     int get_low_period() const
00041     {
00042         return low_period;
00043     }
00044     
00045 private:
00046     InterruptIn interrupt;
00047     Timer high_timer;
00048     Timer low_timer;
00049     volatile int high_period;
00050     volatile int low_period;
00051     
00052     void rising_edge();
00053     void falling_edge();
00054 }; 
00055 
00056 #endif //PULSE_DECODER_H