How to get date from quadratic encoder ?

[JongKim]

Hi, all

I have a parallax incremental rotary encoder. How could I get data from the encoder using LIFA? Is there any Laview code for that?

It was successful to get data from the encoder using just arduino, but I don't know with LIFA.

Thank you in advance.

Sincerely,

Jong

[Nathan_B.]

Quadrature encoders are not supported in the current version of LIFA.  However, it is still possible to add support for them by editing the LIFA Firmware and adding encoder functions as well as making custom LabVIEW functions to access the firmware-side functions that you add.

Could you please post a link to the code that you used to get it to work with the Arduino?

[JongKim]

here is quadratic encoder function, http://www.hessmer.org/blog/2011/01/30/quadrature-encoder-too-fast-for-arduino/

Can you give me a guidance or materials that  help me to study by myself. Thanks.

#include "WProgram.h"

#include <Servo.h>

#include <digitalWriteFast.h>  // library for high performance reads and writes by jrraines

                               // see http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267553811/0

                               // and http://code.google.com/p/digitalwritefast/

// It turns out that the regular digitalRead() calls are too slow and bring the arduino down when

// I use them in the interrupt routines while the motor runs at full speed creating more than

// 40000 encoder ticks per second per motor.

// Quadrature encoders

// Left encoder

#define c_LeftEncoderInterrupt 4

#define c_LeftEncoderPinA 19

#define c_LeftEncoderPinB 25

#define LeftEncoderIsReversed

volatile bool _LeftEncoderBSet;

volatile long _LeftEncoderTicks = 0;

// Right encoder

#define c_RightEncoderInterrupt 5

#define c_RightEncoderPinA 18

#define c_RightEncoderPinB 24

volatile bool _RightEncoderBSet;

volatile long _RightEncoderTicks = 0;

Servo _RightServo;  // create servo object to control right motor

Servo _LeftServo;  // create servo object to control left motor

int potpin = 0;  // analog pin used to connect the potentiometer

int val;    // variable to read the value from the analog pin

void setup()

{

  Serial.begin(115200);

  _RightServo.attach(2);  // attaches the servo on specified pin to the servo object

  _LeftServo.attach(3);  // attaches the servo on specified pin to the servo object

  // Quadrature encoders

  // Left encoder

  pinMode(c_LeftEncoderPinA, INPUT);      // sets pin A as input

  digitalWrite(c_LeftEncoderPinA, LOW);  // turn on pullup resistors

  pinMode(c_LeftEncoderPinB, INPUT);      // sets pin B as input

  digitalWrite(c_LeftEncoderPinB, LOW);  // turn on pullup resistors

  attachInterrupt(c_LeftEncoderInterrupt, HandleLeftMotorInterruptA, RISING);

  // Right encoder

  pinMode(c_RightEncoderPinA, INPUT);      // sets pin A as input

  digitalWrite(c_RightEncoderPinA, LOW);  // turn on pullup resistors

  pinMode(c_RightEncoderPinB, INPUT);      // sets pin B as input

  digitalWrite(c_RightEncoderPinB, LOW);  // turn on pullup resistors

  attachInterrupt(c_RightEncoderInterrupt, HandleRightMotorInterruptA, RISING);

}

void loop()

{

  val = analogRead(potpin);            // reads the value of the potentiometer (value between 0 and 1023)

  val = map(val, 0, 1023, 0, 179);     // scale it to use it with the servo (value between 0 and 180)

  _RightServo.write(val);

  _LeftServo.write(val);

  Serial.print(_LeftEncoderTicks);

  Serial.print("\t");

  Serial.print(_RightEncoderTicks);

  Serial.print("\n");

  delay(20);

}

// Interrupt service routines for the left motor's quadrature encoder

void HandleLeftMotorInterruptA()

{

  // Test transition; since the interrupt will only fire on 'rising' we don't need to read pin A

  _LeftEncoderBSet = digitalReadFast(c_LeftEncoderPinB);   // read the input pin

  // and adjust counter + if A leads B

  #ifdef LeftEncoderIsReversed

    _LeftEncoderTicks -= _LeftEncoderBSet ? -1 : +1;

  #else

    _LeftEncoderTicks += _LeftEncoderBSet ? -1 : +1;

  #endif

}

// Interrupt service routines for the right motor's quadrature encoder

void HandleRightMotorInterruptA()

{

  // Test transition; since the interrupt will only fire on 'rising' we don't need to read pin A

  _RightEncoderBSet = digitalReadFast(c_RightEncoderPinB);   // read the input pin

  // and adjust counter + if A leads B

  #ifdef RightEncoderIsReversed

    _RightEncoderTicks -= _RightEncoderBSet ? -1 : +1;

  #else

    _RightEncoderTicks += _RightEncoderBSet ? -1 : +1;

  #endif

}