IncrementalEncoder.cpp

00001 #include "IncrementalEncoder.h"
00002 
00003 IncrementalEncoder::IncrementalEncoder(PinName pin):  _lastTicks(0),  _ticks(0), _new(false), _interrupt(pin) {
00004     _interrupt.mode(PullNone); // default is pulldown but my encoder board uses a pull-up and that just don't work
00005     _interrupt.rise(this, &IncrementalEncoder::_incRise); 
00006     _interrupt.fall(this, &IncrementalEncoder::_incFall); 
00007     _t.start();
00008     _t.reset();
00009     _lastTime = _t.read_us();
00010 }
00011 
00012 unsigned int IncrementalEncoder::read() {
00013 // disable interrupts?
00014     unsigned int ticks = _ticks - _lastTicks;
00015     _lastTicks = _ticks;
00016     _new=false;
00017     return ticks;
00018 }  
00019 
00020 unsigned int IncrementalEncoder::readTotal() {
00021     _new=false;
00022     return _ticks;
00023 }
00024 
00025 unsigned int IncrementalEncoder::readRise() {
00026     _new=false;
00027     return _rise;
00028 }  
00029 
00030 unsigned int IncrementalEncoder::readFall() {
00031     _new=false;
00032     return _fall;
00033 }
00034     
00035 unsigned int IncrementalEncoder::readTime() {
00036     return _time;
00037 }
00038     
00039 void IncrementalEncoder::reset() {
00040     _ticks = _lastTicks = 0;
00041 }  
00042 
00043 void IncrementalEncoder::_increment() {
00044     _ticks++;
00045 }
00046 
00047 #define A 0.3 // mix in how much from previous readings?
00048 void IncrementalEncoder::_incRise() {
00049     _rise++;
00050     _ticks++;
00051     _new=true;
00052     // compute time between ticks; only do this for rise
00053     // to eliminate jitter
00054     int now = _t.read_us();
00055     _time = A*_time + (1-A)*(now - _lastTime);
00056     // Dead band: if _time > xxxx then turn off and wait until next tick
00057     // to start up again
00058     _lastTime = now;
00059 }
00060 
00061 void IncrementalEncoder::_incFall() {
00062     _fall++;
00063     _ticks++;
00064     _new=true;
00065 }