CPU_Usage.cpp

00001 /******************************************************
00002     CPU_Usage Library V1.0   Ian Weston  15.06.2014
00003     CPU_Usage Library V1.01  Ian Weston  08.01.2016
00004     
00005 A very lightweight tool for calculating the CPU usage
00006 of the mbed micro. Based in the time domain, this will
00007 calculate the percentage of CPU time used.
00008 
00009 Please see the project page for more details.
00010 
00011 Enjoy!
00012 
00013 ******************************************************/
00014 #include "mbed.h"
00015 #include "CPU_Usage.h"
00016 
00017 
00018 // Constructor - time_ballast can be considered as a smoothing
00019 // number, representing time to reset all data. 1 seconds is
00020 // a good place to start.
00021 CPU_Usage::CPU_Usage(Timer &t, float time_ballast) {
00022     _t = &t;
00023     _active = 0;
00024     _inactive = 0;
00025     _time_ballast = time_ballast;
00026     }
00027     
00028 // Use this function when isolating precise areas of code for measurement
00029 // place it at the start of the code of interest    
00030 void CPU_Usage::working(void) {
00031     _t->stop();
00032     _inactive += _t->read();
00033     _t->reset();
00034     _t->start();
00035     }
00036     
00037 // Use this function when isolating precise areas of code for measurement
00038 // place this at the end of the code thats of interest
00039 void CPU_Usage::stopped(void) {
00040     _t->stop();
00041     _active += _t->read();
00042     _t->reset();
00043     _t->start();
00044     }
00045     
00046     
00047 // call this to return the usage value. returns the value as a percentage
00048 uint8_t CPU_Usage::update(void) {
00049     float total = _active + _inactive;
00050     float percentile = 100 / total;
00051     uint8_t usage = _active * percentile;
00052     
00053     if (total > _time_ballast) {
00054         _active = 0;
00055         _inactive = 0;
00056         }
00057     
00058     return usage;
00059     }    
00060     
00061 
00062 // use this function instead of wait() to exclude CPU wait processing from the value.
00063 void CPU_Usage::delay(float duration) {
00064     this->stopped();
00065     wait(duration);
00066     this->working();
00067     }
00068 
00069 // Destructor... empty... as you can see...
00070 CPU_Usage::~CPU_Usage(void) {
00071     
00072     }
00073 
00074 
00075 
00076 
00077