Helmut Schmücker / FtEncoder

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Dependencies:   NeedfulThings

FtEncoder.cpp@2:1bf9f7b6bf29, 2013-03-25 (annotated)

Committer:
humlet
Date:
Mon Mar 25 21:08:56 2013 +0000
Revision:
2:1bf9f7b6bf29
Parent:
1:9e595056c3da 
introduction of NeedfulThings lib

Who changed what in which revision?

UserRevisionLine numberNew contents of line
humlet 0:8cb1142a88d5 1 #include "FtEncoder.h"
humlet 0:8cb1142a88d5 2
humlet 0:8cb1142a88d5 3 FtEncoder::FtEncoder(PinName pwm, unsigned int standStillTimeout)
humlet 1:9e595056c3da 4 :m_encIRQ(pwm),
humlet 1:9e595056c3da 5 m_cnt(0),
humlet 1:9e595056c3da 6 m_standStillTimeout(standStillTimeout),
humlet 1:9e595056c3da 7 m_cursor(0)
humlet 0:8cb1142a88d5 8 {
humlet 1:9e595056c3da 9 // initialize the edge timestamp ringbuffer
humlet 0:8cb1142a88d5 10 unsigned int tmStmp = getCurrentTimeStamp() - c_nTmStmps * m_standStillTimeout;
humlet 1:9e595056c3da 11 for(int i=0; i<c_nTmStmps; ++i)
humlet 0:8cb1142a88d5 12 m_timeStamps[i] = tmStmp + i*m_standStillTimeout;
humlet 0:8cb1142a88d5 13 m_cursor = c_nTmStmps-1;
humlet 0:8cb1142a88d5 14
humlet 1:9e595056c3da 15 m_encIRQ.mode(PullUp); // set it to pullup, but an external pullup is needed, the internal isn't sufficient
humlet 0:8cb1142a88d5 16 m_encIRQ.rise(this, &FtEncoder::encoderISR);
humlet 0:8cb1142a88d5 17 m_encIRQ.fall(this, &FtEncoder::encoderISR);
humlet 1:9e595056c3da 18 m_tmOut.attach_us(this, &FtEncoder::timeoutISR, m_standStillTimeout);
humlet 0:8cb1142a88d5 19 }
humlet 0:8cb1142a88d5 20
humlet 0:8cb1142a88d5 21 unsigned int FtEncoder::getLastPeriod() const
humlet 0:8cb1142a88d5 22 {
humlet 0:8cb1142a88d5 23 unsigned int period = 0;
humlet 0:8cb1142a88d5 24 unsigned int cursor, cnt;
humlet 0:8cb1142a88d5 25 do {
humlet 0:8cb1142a88d5 26 cursor = m_cursor;
humlet 0:8cb1142a88d5 27 cnt = m_cnt;
humlet 0:8cb1142a88d5 28 period = m_timeStamps[m_cursor] - m_timeStamps[(m_cursor-2)&(c_nTmStmps-1)];
humlet 1:9e595056c3da 29 } while(cursor!=m_cursor || cnt!=m_cnt); // stay in loop until we have a non intrrupted reading
humlet 0:8cb1142a88d5 30 return period;
humlet 0:8cb1142a88d5 31 }
humlet 0:8cb1142a88d5 32
humlet 0:8cb1142a88d5 33 float FtEncoder::getSpeed() const
humlet 0:8cb1142a88d5 34 {
humlet 0:8cb1142a88d5 35 unsigned int period = getLastPeriod();
humlet 0:8cb1142a88d5 36 return (period!=0 && period<m_standStillTimeout) ?
humlet 0:8cb1142a88d5 37 c_speedFactor/period : 0.0;
humlet 0:8cb1142a88d5 38 }
humlet 0:8cb1142a88d5 39
humlet 0:8cb1142a88d5 40 void FtEncoder::encoderISR()
humlet 0:8cb1142a88d5 41 {
humlet 0:8cb1142a88d5 42 ++m_cursor;
humlet 0:8cb1142a88d5 43 m_cursor &= c_nTmStmps-1;
humlet 0:8cb1142a88d5 44 m_timeStamps[m_cursor] = getCurrentTimeStamp();
humlet 1:9e595056c3da 45 // restart the timeout
humlet 2:1bf9f7b6bf29 46 m_tmOut.remove();
humlet 2:1bf9f7b6bf29 47 m_tmOut.insert(m_timeStamps[m_cursor]+m_standStillTimeout);
humlet 1:9e595056c3da 48 ++m_cnt;
humlet 0:8cb1142a88d5 49 m_callBack.call();
humlet 1:9e595056c3da 50 }
humlet 1:9e595056c3da 51
humlet 1:9e595056c3da 52 void FtEncoder::timeoutISR(){
humlet 1:9e595056c3da 53 --m_cnt;
humlet 1:9e595056c3da 54 encoderISR();
humlet 0:8cb1142a88d5 55 }