Timer_PIT.h

00001 /* Timer_PIT.h
00002  * Tested with mbed board: FRDM-KL46Z
00003  * Author: Mark Gottscho
00004  * mgottscho@ucla.edu
00005  */
00006 
00007 #ifndef TIMER_PIT_H
00008 #define TIMER_PIT_H
00009 
00010 #include "mbed.h"
00011 #include "HardwareTimer.h"
00012 #include "PreciseTime.h"
00013 
00014 /**
00015  * Base class for PIT timing on the FRDM-KL46Z.
00016  */
00017 class Timer_PIT : public HardwareTimer {
00018     public:
00019         /**
00020          * Construct a new PIT timer. The timer operates at 1 KHz. Only one Timer_PIT
00021          * object may be valid at a time (can control hardware).
00022          */
00023         Timer_PIT();
00024         
00025         /**
00026          * Destroy the PIT object. If the object was valid (was allowed to access the timer
00027          * hardware), it will free the resource so that another Timer_PIT object can access
00028          * hardware.
00029          */
00030         virtual ~Timer_PIT();
00031 
00032         virtual uint32_t getTick ();
00033     
00034     private:        
00035         virtual void __init_timer();
00036         virtual void __start_timer();
00037         virtual void __stop_timer();
00038         virtual void __timer_isr();
00039         
00040         /** 
00041          * We need a static function to use as interrupt service routine.
00042          * Although we would ideally like to use a member function of Timer_PIT,
00043          * we need to wrap it instead.
00044          */
00045         static void __pit_isr_wrapper();
00046                 
00047         static bool __pit_used; //This flag ensures that no two Timer_PIT objects attempt to manipulate the hardware at once
00048         static Timer_PIT *__obj; //if __tpm_used is true, this should point to the valid Timer_PIT object. This helps with the ISR wrapper.
00049 };
00050 
00051 #endif