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Bernard

MSP430G2553 and Rotary encoder

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Hello,

 

I am trying to use rotary library for my VFO ad9850.

Originally writen for Arduino I just changed PCINT for PORT2_VECTOR interrupt.

so far  can say it almost works but I get some issues I cannot understand

Here is my test code :

/*
encoder_test.ino
Energia 011
MSP430G2553 launchpad ver 1.5
Windows 7
Rotary encoder KY-040
*/

#include <msp430g2553.h>
#include "rotary.h"

Rotary r = Rotary(P2_1, P2_2);

void setup()
{
  Serial.begin(9600);
  P2DIR &= ~(BIT1 + BIT2);
  P2IES = BIT1 + BIT2 ; //high to  low transition
  P2OUT |= BIT1 + BIT2;
  P2REN = BIT1 + BIT2;
  P2IE = BIT1 + BIT2; 
  P2IFG &= ~BIT1 + BIT2; 
  _BIS_SR(GIE); 
}

void loop()
{    
}

#pragma vector=PORT2_VECTOR
__interrupt void port_2 (void) {
  unsigned char result = r.process();
  if (result) {
    Serial.println(result == DIR_CW ? "Right" : "Left");
  }
  P2IFG &= ~BIT1 + BIT2; // P2.1 P2.2 interrupt flag cleared  
}

rotary.h

/*
 * Rotary encoder library for Arduino.
 */

#ifndef rotary_h
#define rotary_h

#include "Energia.h"

// Enable this to emit codes twice per step.
#define HALF_STEP

// Values returned by 'process'
// No complete step yet.
#define DIR_NONE 0x0
// Clockwise step.
#define DIR_CW 0x10
// Anti-clockwise step.
#define DIR_CCW 0x20

class Rotary
{
public:
  Rotary(char, char);
  // Process pin(s)
  unsigned char process();
private:
  unsigned char state;
  unsigned char pin1;
  unsigned char pin2;
};

#endif

rotary.cpp

/* Rotary encoder handler for arduino. v1.1
 *
 * Copyright 2011 Ben Buxton. Licenced under the GNU GPL Version 3.
 * Contact: bb@cactii.net
 *
 * A typical mechanical rotary encoder emits a two bit gray code
 * on 3 output pins. Every step in the output (often accompanied
 * by a physical 'click') generates a specific sequence of output
 * codes on the pins.
 *
 * There are 3 pins used for the rotary encoding - one common and
 * two 'bit' pins.
 *
 * The following is the typical sequence of code on the output when
 * moving from one step to the next:
 *
 *   Position   Bit1   Bit2
 *   ----------------------
 *     Step1     0      0
 *      1/4      1      0
 *      1/2      1      1
 *      3/4      0      1
 *     Step2     0      0
 *
 * From this table, we can see that when moving from one 'click' to
 * the next, there are 4 changes in the output code.
 *
 * - From an initial 0 - 0, Bit1 goes high, Bit0 stays low.
 * - Then both bits are high, halfway through the step.
 * - Then Bit1 goes low, but Bit2 stays high.
 * - Finally at the end of the step, both bits return to 0.
 *
 * Detecting the direction is easy - the table simply goes in the other
 * direction (read up instead of down).
 *
 * To decode this, we use a simple state machine. Every time the output
 * code changes, it follows state, until finally a full steps worth of
 * code is received (in the correct order). At the final 0-0, it returns
 * a value indicating a step in one direction or the other.
 *
 * It's also possible to use 'half-step' mode. This just emits an event
 * at both the 0-0 and 1-1 positions. This might be useful for some
 * encoders where you want to detect all positions.
 *
 * If an invalid state happens (for example we go from '0-1' straight
 * to '1-0'), the state machine resets to the start until 0-0 and the
 * next valid codes occur.
 *
 * The biggest advantage of using a state machine over other algorithms
 * is that this has inherent debounce built in. Other algorithms emit spurious
 * output with switch bounce, but this one will simply flip between
 * sub-states until the bounce settles, then continue along the state
 * machine.
 * A side effect of debounce is that fast rotations can cause steps to
 * be skipped. By not requiring debounce, fast rotations can be accurately
 * measured.
 * Another advantage is the ability to properly handle bad state, such
 * as due to EMI, etc.
 * It is also a lot simpler than others - a static state table and less
 * than 10 lines of logic.
 */

#include "Energia.h"
#include "rotary.h"

/*
 * The below state table has, for each state (row), the new state
 * to set based on the next encoder output. From left to right in,
 * the table, the encoder outputs are 00, 01, 10, 11, and the value
 * in that position is the new state to set.
 */

#define R_START 0x0

#ifdef HALF_STEP
// Use the half-step state table (emits a code at 00 and 11)
#define R_CCW_BEGIN 0x1
#define R_CW_BEGIN 0x2
#define R_START_M 0x3
#define R_CW_BEGIN_M 0x4
#define R_CCW_BEGIN_M 0x5
const unsigned char ttable[6][4] = {
  // R_START (00)
  {
    R_START_M,            R_CW_BEGIN,     R_CCW_BEGIN,  R_START  }
  ,
  // R_CCW_BEGIN
  {
    R_START_M | DIR_CCW, R_START,        R_CCW_BEGIN,  R_START  }
  ,
  // R_CW_BEGIN
  {
    R_START_M | DIR_CW,  R_CW_BEGIN,     R_START,      R_START  }
  ,
  // R_START_M (11)
  {
    R_START_M,            R_CCW_BEGIN_M,  R_CW_BEGIN_M, R_START  }
  ,
  // R_CW_BEGIN_M
  {
    R_START_M,            R_START_M,      R_CW_BEGIN_M, R_START | DIR_CW  }
  ,
  // R_CCW_BEGIN_M
  {
    R_START_M,            R_CCW_BEGIN_M,  R_START_M,    R_START | DIR_CCW  }
  ,
};
#else
// Use the full-step state table (emits a code at 00 only)
#define R_CW_FINAL 0x1
#define R_CW_BEGIN 0x2
#define R_CW_NEXT 0x3
#define R_CCW_BEGIN 0x4
#define R_CCW_FINAL 0x5
#define R_CCW_NEXT 0x6

const unsigned char ttable[7][4] = {
  // R_START
  {
    R_START,    R_CW_BEGIN,  R_CCW_BEGIN, R_START  }
  ,
  // R_CW_FINAL
  {
    R_CW_NEXT,  R_START,     R_CW_FINAL,  R_START | DIR_CW  }
  ,
  // R_CW_BEGIN
  {
    R_CW_NEXT,  R_CW_BEGIN,  R_START,     R_START  }
  ,
  // R_CW_NEXT
  {
    R_CW_NEXT,  R_CW_BEGIN,  R_CW_FINAL,  R_START  }
  ,
  // R_CCW_BEGIN
  {
    R_CCW_NEXT, R_START,     R_CCW_BEGIN, R_START  }
  ,
  // R_CCW_FINAL
  {
    R_CCW_NEXT, R_CCW_FINAL, R_START,     R_START | DIR_CCW  }
  ,
  // R_CCW_NEXT
  {
    R_CCW_NEXT, R_CCW_FINAL, R_CCW_BEGIN, R_START  }
  ,
};
#endif

/*
 * Constructor. Each arg is the pin number for each encoder contact.
 */
Rotary::Rotary(char _pin1, char _pin2) {
  // Assign variables.
  pin1 = _pin1;
  pin2 = _pin2;

  // initialisation in the main

  // Initialise state.
  state = R_START;
}

unsigned char Rotary::process() {
  // Grab state of input pins.
  unsigned char pinstate = (digitalRead(pin2) << 1) | digitalRead(pin1);
  // Determine new state from the pins and state table.
  state = ttable[state & 0xf][pinstate];
  // Return emit bits, ie the generated event.
  return state & 0x30;
}


Sometimes I get LEFT among RIGHT et vice versa .

 

Turning knob very fast freezes the program.

 

Any help would be appreciate.

 

Salutations

Bernard

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Serial print can be very slow and should be avoided inside an interrupt routine.

 

Better to write the state/result into a global variable (declared with the "volatile" prefix) and process it in the main loop. You might need to add some additional logic to detect whether the encoder is still moving, e.g. by setting a flag in interrupt routine and resetting it in the main loop.

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