Diff: FtEncoder.h

Revision:

0:8cb1142a88d5

Child:

1:9e595056c3da

diff -r 000000000000 -r 8cb1142a88d5 FtEncoder.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FtEncoder.h	Thu Mar 14 18:27:24 2013 +0000
@@ -0,0 +1,76 @@
+#ifndef FTENCODER_H
+#define FTENCODER_H
+
+#include "InterruptIn.h"
+#include "us_ticker_api.h"
+#include "FunctionPointer.h"
+#include "Timeout.h"
+
+using namespace mbed;
+
+/// Simple Interface for the encoder of the red fischertechnik motors
+/// @note 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.
+/// 
+class FtEncoder
+{
+    static const float c_speedFactor = 1e6/75.0; // 1/(µs * 150/2) edges per revolution)
+    static const int c_nTmStmps = 1<<2;
+
+    InterruptIn m_encIRQ;
+    Timeout m_tmOut;
+
+    volatile unsigned int m_cnt;
+    unsigned int m_standStillTimeout;
+    volatile unsigned int m_cursor;
+    unsigned int m_timeStamps[c_nTmStmps];
+    bool m_ready;
+
+    FunctionPointer m_callBack;
+
+    /// ISR called on rising and falling encoder edges
+    void encoderISR();
+
+public:
+
+    /// create a simple interface to the encoder connected to the given pin
+    /// @param name of the pin the black encoder signl wire is connected to
+    /// @param standStillTimeout After this time [µs] without any encoder edge getSpeed() returns zero
+    FtEncoder(PinName pwm, unsigned int standStillTimeout=50000);
+
+    /// get number of falling and rising encoder edges
+    inline unsigned int getCounter() const {
+        return m_cnt;
+    };
+
+    /// reset the encoder edge counter to the given value (default is 0)
+    inline void resetCounter(unsigned int cnt=0) {
+        m_cnt=cnt;
+    };
+
+    /// get period [µs] between the two latest edges of same direction (rising or falling)
+    /// @note Returns standStillTimeout if motor stands still or no edges have been detected yet
+    unsigned int getLastPeriod() const;
+
+    /// get time stamp [µs] of last update i.e. encoder edge or timeout
+    unsigned int getTimeStampOfLastUpdate() const {
+        return m_timeStamps[m_cursor];
+    };
+
+    /// returns current time stamp [µs]
+    /// @note simply calls us_ticker_read() from mbed's C-API (capi/us_ticker_api.h)
+    inline unsigned int  getCurrentTimeStamp() const {
+        return us_ticker_read();
+    }
+
+    /// get speed in revolutions per second (Hz)
+    float getSpeed() const;
+
+    /// hook in a call back to the encoder ISR e.g. for sending a RTOS signal
+    void setCallBack(FunctionPointer callBack) {
+        m_callBack=callBack;
+    };
+};
+
+#endif
\ No newline at end of file