quadratureEncoder.cpp

00001 /*
00002 name:                encoder.h
00003 date:                04-june-2011
00004 header description:  contains functions and external variables to interface quadrature encoder
00005 compiler-library:    the mbed library interface is used on the whole..
00006 compatability:       can also be compatable with generalised code with diffrerent hardware and software
00007 hardware dependency: works on rover 5 model platform interfaced with mbed controller
00008 
00009 indentation:         <mbed default intendation - 4 spaces>
00010 resources:          http://www.sparkfun.com/products/10336
00011                     http://letsmakerobots.com/node/24031
00012                     http://www.sparkfun.com/datasheets/Robotics/Rover%205%20Introduction.pdf
00013             */
00014 #include "mbed.h"
00015 #include "quadratureEncoder.h"
00016 //gets a bit position by shifting 1
00017 #define Abit   0
00018 #define Bbit   1
00019 
00020 #define _BV(x) (1 << x)
00021 
00022 // sbi sets a particular bit and cbi clears the bit (target byte-word, bit position)
00023 #define sbi(y,x) y|=_BV(x)
00024 #define cbi(y,x) y&=~_BV(x)
00025 
00026 quadratureEncoder::quadratureEncoder(PinName pinA, PinName pinB):
00027 _pinA(pinA), _pinB(pinB){
00028     _pinA.rise(this, &quadratureEncoder::ARise);
00029     _pinA.fall(this, &quadratureEncoder::AFall);
00030     _pinB.rise(this, &quadratureEncoder::BRise);
00031     _pinB.fall(this, &quadratureEncoder::BFall);
00032     
00033     _oldState = 0x00;
00034     _nowState = 0x00;
00035     _moved = 0;
00036     _count = 0;
00037 }
00038 
00039 ////////////////////////////////////////////////////////////////////////////////////////
00040 int quadratureEncoder::getCount() {
00041     return _count;
00042 }
00043 
00044 void quadratureEncoder::resetCount() {
00045     _count = 0;
00046 }
00047 
00048 void quadratureEncoder::setCount(int setCounter) {
00049     _count = setCounter;
00050 }
00051 
00052 
00053 
00054 ////////////////////////////////////////////////////////////////////////////////////////
00055 void quadratureEncoder::resetMoved() {
00056     _moved = 0;
00057 }
00058 
00059 void quadratureEncoder::setMoved(int setMover) {
00060     _moved = setMover;
00061 }
00062 
00063 int quadratureEncoder::getMoved() {
00064     return _moved;
00065 }
00066 
00067 ////////////////////////////////////////////////////////////////////////////////////////
00068 char quadratureEncoder::saveState(char nowS) {
00069     return nowS;
00070 }
00071 
00072 char quadratureEncoder::getBit(char bitP, char targB) {
00073     targB = targB & _BV(bitP);
00074     if (targB == 0)
00075         return 0;
00076     else
00077         return 1;
00078 }
00079 
00080 
00081 /*
00082 function:   the following 8 functions are ISR called by rise and fall of 4 pins
00083 input:      none (interupt called)
00084 output:     none
00085 functioning:interrupts are called when the pin change occours
00086             sets or clears the respective bit
00087             checks the previous state and increments respective direction
00088             restores new state value into old state
00089             increments a count value for processing    */
00090 void quadratureEncoder::ARise() {
00091     sbi(_nowState,Abit);
00092     if (getBit(Bbit,_oldState)==0 && getBit(Abit,_oldState)==0)
00093         _moved++;
00094     else if (getBit(Bbit,_oldState)==0 && getBit(Abit,_oldState)==1)
00095         _moved--;
00096     _oldState = saveState(_nowState);
00097     _count++;
00098 }
00099 
00100 void quadratureEncoder::AFall() {
00101     cbi(_nowState, Abit);
00102     if (getBit(Bbit,_oldState)==1 && getBit(Abit,_oldState)==1)
00103         _moved++;
00104     else if (getBit(Bbit,_oldState)==1 && getBit(Abit,_oldState)==0)
00105         _moved--;
00106     _oldState = saveState(_nowState);
00107     _count++;
00108 }
00109 
00110 void quadratureEncoder::BRise() {
00111     sbi(_nowState,Bbit);
00112     if (getBit(Bbit,_oldState)==1 && getBit(Abit,_oldState)==0)
00113         _moved++;
00114     else if (getBit(Bbit,_oldState)==0 && getBit(Abit,_oldState)==0)
00115         _moved--;
00116     _oldState = saveState(_nowState);
00117     _count++;
00118 }
00119 
00120 void quadratureEncoder::BFall() {
00121     cbi(_nowState, Bbit);
00122     if (getBit(Bbit,_oldState)==0 && getBit(Abit,_oldState)==1)
00123         _moved++;
00124     else if (getBit(Bbit,_oldState)==1 && getBit(Abit,_oldState)==1)
00125         _moved--;
00126     _oldState = saveState(_nowState);
00127     _count++;
00128 }
00129