Zoltan Hudak / Manchester Featured

Manchester code (phase encoding) library.

Dependents:   Manchester_Transmitter Manchester_Receiver

Manchester code (phase encoding) library

It implements Manchester code according to both IEEE 802.3 and G.E. Thomas' conventions.

  • A '0' is expressed by a high-to-low transition, a '1' by low-to-high transition in the IEEE 802.3 convention. The reverse is true in the G.E. Thomas' convention.
  • The transitions which signify '0' or '1' occur at the midpoint of a period.
  • Transitions at the start of a period are overhead and don't signify data.
  • Least significant bit is sent first
  • There are synchronization pulses (the number can be set) at the begin of transmission

    Select a convention to be used by commenting or uncommenting the line below in the Manchester.h header file.

Manchester.h

#define G_E_THOMAS 1

The IEEE 802.3 convention is used by default.

A Manchester encoded message (using G.E. Thomas' convention), with one sync pulse in the preamble, carrying four bytes:

/media/uploads/hudakz/manchester01.png

ACKNOWLEDGEMENT: The code in this library was based on this article published by Robert Guastella.

Import programManchester_Transmitter

Manchester transmitter demo.

Last commit 14 Oct 2018 by Zoltan Hudak


Import programManchester_Receiver

Manchester receiver demo.

Last commit 14 Oct 2018 by Zoltan Hudak

NOTE: To perform a simple test (without radio modules) connect the txPin on transmitter board to the rxPin on the receiver board and make sure that grounds are also connected one another.

Diff: Manchester.h

Revision:
8:c1b5893191fe
Parent:
6:7454ad91f714
--- a/Manchester.h	Sun Sep 03 09:04:18 2017 +0000
+++ b/Manchester.h	Sun Oct 14 09:38:33 2018 +0000
@@ -25,7 +25,6 @@
  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-
 /*
    This library implements Manchester code according to both IEEE 802.3 
    and G.E. Thomas' conventions. 
@@ -40,15 +39,14 @@
    Select a convention to be used by commenting or uncommenting 
    the line "#define G_E_THOMAS 1" below. 
 */
-
 #ifndef MANCHESTER_H
 #define MANCHESTER_H
 
 #include "mbed.h"
 #include "ManchesterMsg.h"
 
+//Uncomment the following line to use G.E.Thomas' convention
 
-//Uncomment the following line to use G.E.Thomas' convention
 //#define G_E_THOMAS 1
 
 class   Manchester
@@ -63,40 +61,46 @@
         TRANSITION,
         COMPLETE,
         LISTEN,
+        DECODE_START,
         DECODE,
+        STOP,
         ERROR
     };
-
 public:
     Manchester
     (
         PinName     txPin,          /* transmitter pin name */
         PinName     rxPin,          /* receiver pin name */
         uint32_t    speed = 1200,   /* speed in bits per second */
-        uint8_t     tol   = 25      /* pulse width tolerance (+/-) in % */
+        uint8_t     tol = 25,       /* pulse width tolerance (+/-) in % */
+        float       rxTimeout = 5   /* receive timeout */
     );
-    ~Manchester(void) { }
+    ~       Manchester(void)    { }
     void    transmit(ManchesterMsg& msg);
     bool    receive(ManchesterMsg& msg);
-
+    void    setPreamble(uint8_t preamble)   { _preamble = preamble; }
+    void    setRxTimeout(float seconds)     { _rxTimeout = seconds; }
+    char*   lastError()                     { return _error; }
 private:
-    DigitalOut  _tx;            // transmitter line
-    InterruptIn _rx;            // receiver line
-    Ticker      _txTicker;      // transmitter ticker
-    Timeout     _timeout;       // timeout (watchdog)
-    uint32_t    _midBitTime;    // mid-bit time [us]
-    uint32_t    _minPulseWidth; // minimum pulse width [us]
-    uint32_t    _maxPulseWidth; // maximum pulse width [us]
-    State       _state;         // state
-    char*       _data;          // data array
-    size_t      _len;           // data length in bytes
-    size_t      _maxLen;        // maximum length
-
+    DigitalOut  _tx;                // transmitter line
+    InterruptIn _rx;                // receiver line
+    Ticker      _txTicker;          // transmitter ticker
+    Timeout     _timeout;           // timeout (watchdog)
+    Timer       _timer;
+    uint32_t    _midBitTime;        // mid-bit time [us]
+    uint32_t    _minPulseWidth;     // minimum pulse width [us]
+    uint32_t    _maxPulseWidth;     // maximum pulse width [us]
+    uint32_t    _tol;
+    float       _rxTimeout;         // reception timeout [s]
+    State       _state;             // state
+    char*       _data;              // data array
+    size_t      _len;               // data length in bytes
+    size_t      _maxLen;            // maximum length
+    size_t      _preamble;          // number of start patterns
+    char*       _error;
     void        transmission(void);
     void        reception(void);
-    void        txTimeout(void);
-    void        rxTimeout(void);
+    void        onTxTimeout(void);
+    void        onRxTimeout(void);
 };
 #endif // MANCHESTER_H
-
-