PwmReader.cpp

00001 #include "PwmReader.h"
00002 
00003 //Constructors
00004 PwmReader::PwmReader(PinName pwmInPort, float min, float max)
00005 {
00006     if (min > max)
00007     {
00008         error("PwmReader min value greater than max value!");
00009     }
00010     
00011     di = new InterruptIn(pwmInPort);
00012     pwmMin = min;
00013     pwmMax = max;
00014     lastRise = 0;
00015     period = 0;
00016     duty = 0.0;
00017     di->mode(PullDown);
00018     di->rise(this,&PwmReader::pwmRise);  // attach the address of the flip function to the rising edge
00019     di->fall(this,&PwmReader::pwmFall);
00020     
00021     t.start();
00022 }
00023 
00024 PwmReader::~PwmReader()
00025 {
00026     delete di;
00027     t.stop();
00028 }
00029 
00030 // public methods
00031 float PwmReader::getDuty()
00032 {
00033     float smallDelta = (duty > pwmMin) ? (duty - pwmMin) : 0.0;
00034     float dutyAdjusted = smallDelta / (pwmMax-pwmMin);
00035     return dutyAdjusted;
00036 }
00037 
00038 // private methods
00039 void PwmReader::pwmRise()
00040 {
00041     int rise = t.read_us();
00042     if( (lastRise > 0) && (rise > lastRise) ) {
00043         period = rise - lastRise;
00044     }
00045     lastRise = rise;
00046 
00047 }
00048 
00049 void PwmReader::pwmFall()
00050 {
00051     int fall = t.read_us();
00052     if(period > 0 ) {
00053         int delta = fall - lastRise;
00054         duty = float(delta)/float(period); 
00055     }
00056 }