freq_task.cpp

00001 /**
00002  * Task for getting the frequency from digital input on pin13. 
00003  * The frequency is calculated by counting the number of rises
00004  * on the pin. This is done using an interupt handler.
00005  *
00006  * Author: Jacob Baungard Hansen
00007  */
00008 #include "freq_task.h"
00009 
00010 FrequencyTask::FrequencyTask(int starting_offset, int frequency_ms,
00011                                                                      State * state)
00012                                     : Task(starting_offset, frequency_ms) {
00013                                         
00014     this->state = state;
00015     this->count = 0;
00016     this->interrupt = new InterruptIn(p13); 
00017 
00018 }
00019 
00020 FrequencyTask::~FrequencyTask() {
00021     delete this->interrupt;
00022 }
00023 
00024 /**
00025  * This is called by the interupt, simply adds one to the count
00026  */
00027 void FrequencyTask::counter() {
00028     this->count++;
00029 }
00030 
00031 void FrequencyTask::action() {
00032     // reset the count
00033     this->count=0;
00034     // Enable the iterrupt
00035     this->interrupt->rise<FrequencyTask>(this, &FrequencyTask::counter);
00036     // wait for a specied amout of time
00037     wait_ms(SAMPLE_LENGTH_MS);
00038     // disable interrupts
00039     this->interrupt->rise(NULL);
00040     //interupt.rise<FrequencyTask>(this, NULL); This crashes, should report bug to ARM
00041     int freq = 0;
00042     if (this->count > 0) {
00043         freq = count/(SAMPLE_LENGTH_MS*0.001);
00044     }
00045     
00046     this->state->set_freq(freq);
00047 }