Helmut Schmücker / FtEncoder

Interface for the encoder of the red fischertechnik motors

Dependencies:   NeedfulThings

Simple Interface for the simple encoder of the red fischertechnik motors.

The interface counts both, rising and falling edges, resulting in 150 counts per revolution. The interface also provides a speed measurement updated with each edge.

Connect the green wire to GND, the red one to +3.3V and the black signal line to any of mbed numbered pins. Additionally connect the signal line via a pullup resitor to +3.3V. A 10K resistor works fine.

FtEncoder.h@3:3944952c9eab, 2013-03-25 (annotated)

Committer:
humlet
Date:
Mon Mar 25 21:47:38 2013 +0000
Revision:
3:3944952c9eab
Parent:
2:1bf9f7b6bf29 
Added NeedfulThings lib  dependency (hopefully)

Who changed what in which revision?

UserRevisionLine numberNew contents of line
humlet 0:8cb1142a88d5 1 #ifndef FTENCODER_H
humlet 0:8cb1142a88d5 2 #define FTENCODER_H
humlet 0:8cb1142a88d5 3
humlet 0:8cb1142a88d5 4 #include "InterruptIn.h"
humlet 0:8cb1142a88d5 5 #include "us_ticker_api.h"
humlet 0:8cb1142a88d5 6 #include "FunctionPointer.h"
humlet 2:1bf9f7b6bf29 7 #include "TimeoutTweaked.h"
humlet 0:8cb1142a88d5 8
humlet 0:8cb1142a88d5 9 using namespace mbed;
humlet 0:8cb1142a88d5 10
humlet 1:9e595056c3da 11 /// Simple Interface for the simple encoder of the red fischertechnik motors.
humlet 1:9e595056c3da 12 /// The interface counts both, rising and falling edges, resulting in 150 counts per revolution.
humlet 1:9e595056c3da 13 /// The interface also provides a speed measurement updated with each edge.
humlet 0:8cb1142a88d5 14 /// @note Connect the green wire to GND, the red one to +3.3V and the
humlet 0:8cb1142a88d5 15 /// black signal line to any of mbed numbered pins. Additionally connect the signal line
humlet 0:8cb1142a88d5 16 /// via a pullup resitor to +3.3V. A 10K resistor works fine.
humlet 0:8cb1142a88d5 17 ///
humlet 0:8cb1142a88d5 18 class FtEncoder
humlet 0:8cb1142a88d5 19 {
humlet 1:9e595056c3da 20 static const float c_speedFactor = 1e6/75.0; /// 1/(µs * 150/2) edges per revolution)
humlet 1:9e595056c3da 21 static const int c_nTmStmps = 1<<2; /// size of ringbuffer: Has to be 2^x
humlet 0:8cb1142a88d5 22
humlet 0:8cb1142a88d5 23 InterruptIn m_encIRQ;
humlet 2:1bf9f7b6bf29 24 TimeoutTweaked m_tmOut;
humlet 0:8cb1142a88d5 25
humlet 1:9e595056c3da 26 volatile unsigned int m_cnt; /// edge counter
humlet 1:9e595056c3da 27 unsigned int m_standStillTimeout;
humlet 1:9e595056c3da 28 volatile unsigned int m_cursor; /// ringbuffer cursor
humlet 2:1bf9f7b6bf29 29 volatile uint32_t m_timeStamps[c_nTmStmps]; /// ringbuffer of edge timestamps
humlet 0:8cb1142a88d5 30
humlet 0:8cb1142a88d5 31 FunctionPointer m_callBack;
humlet 0:8cb1142a88d5 32
humlet 0:8cb1142a88d5 33 /// ISR called on rising and falling encoder edges
humlet 0:8cb1142a88d5 34 void encoderISR();
humlet 1:9e595056c3da 35 /// ISR called on edge timeout i.e. standstill
humlet 1:9e595056c3da 36 void timeoutISR();
humlet 0:8cb1142a88d5 37
humlet 0:8cb1142a88d5 38 public:
humlet 0:8cb1142a88d5 39
humlet 0:8cb1142a88d5 40 /// create a simple interface to the encoder connected to the given pin
humlet 1:9e595056c3da 41 /// @param name of the pin the black encoder signal wire is connected to
humlet 0:8cb1142a88d5 42 /// @param standStillTimeout After this time [µs] without any encoder edge getSpeed() returns zero
humlet 0:8cb1142a88d5 43 FtEncoder(PinName pwm, unsigned int standStillTimeout=50000);
humlet 0:8cb1142a88d5 44
humlet 0:8cb1142a88d5 45 /// get number of falling and rising encoder edges
humlet 0:8cb1142a88d5 46 inline unsigned int getCounter() const {
humlet 0:8cb1142a88d5 47 return m_cnt;
humlet 0:8cb1142a88d5 48 };
humlet 0:8cb1142a88d5 49
humlet 0:8cb1142a88d5 50 /// reset the encoder edge counter to the given value (default is 0)
humlet 0:8cb1142a88d5 51 inline void resetCounter(unsigned int cnt=0) {
humlet 0:8cb1142a88d5 52 m_cnt=cnt;
humlet 0:8cb1142a88d5 53 };
humlet 0:8cb1142a88d5 54
humlet 0:8cb1142a88d5 55 /// get period [µs] between the two latest edges of same direction (rising or falling)
humlet 0:8cb1142a88d5 56 /// @note Returns standStillTimeout if motor stands still or no edges have been detected yet
humlet 0:8cb1142a88d5 57 unsigned int getLastPeriod() const;
humlet 0:8cb1142a88d5 58
humlet 0:8cb1142a88d5 59 /// get time stamp [µs] of last update i.e. encoder edge or timeout
humlet 0:8cb1142a88d5 60 unsigned int getTimeStampOfLastUpdate() const {
humlet 0:8cb1142a88d5 61 return m_timeStamps[m_cursor];
humlet 0:8cb1142a88d5 62 };
humlet 0:8cb1142a88d5 63
humlet 0:8cb1142a88d5 64 /// returns current time stamp [µs]
humlet 0:8cb1142a88d5 65 /// @note simply calls us_ticker_read() from mbed's C-API (capi/us_ticker_api.h)
humlet 0:8cb1142a88d5 66 inline unsigned int getCurrentTimeStamp() const {
humlet 0:8cb1142a88d5 67 return us_ticker_read();
humlet 0:8cb1142a88d5 68 }
humlet 0:8cb1142a88d5 69
humlet 0:8cb1142a88d5 70 /// get speed in revolutions per second (Hz)
humlet 0:8cb1142a88d5 71 float getSpeed() const;
humlet 0:8cb1142a88d5 72
humlet 0:8cb1142a88d5 73 /// hook in a call back to the encoder ISR e.g. for sending a RTOS signal
humlet 0:8cb1142a88d5 74 void setCallBack(FunctionPointer callBack) {
humlet 0:8cb1142a88d5 75 m_callBack=callBack;
humlet 0:8cb1142a88d5 76 };
humlet 0:8cb1142a88d5 77 };
humlet 0:8cb1142a88d5 78
humlet 0:8cb1142a88d5 79 #endif