Rotary Encoder Issue

Projects General Guidance
1 
#include <Wire.h>

#define encoder0PinA  3
#define encoder0PinB  2

volatile unsigned int encoder0Pos = 0;
int value = 0;

void setup() { 

  pinMode(encoder0PinA, INPUT); 
  digitalWrite(encoder0PinA, HIGH);       // turn on pullup resistor
  pinMode(encoder0PinB, INPUT); 
  digitalWrite(encoder0PinB, HIGH);       // turn on pullup resistor

  attachInterrupt(0, doEncoder, HIGH);  // encoder pin on interrupt 0 - pin 2
 Wire.begin();                // set up I2C on 4 and 5 analog
  Wire.beginTransmission(0x09);// join I2C, talk to BlinkM 0x09
  Wire.send("o");     
 Wire.endTransmission(); 
   
  Wire.beginTransmission(0x09);
  Wire.send("c");
  Wire.send(0xff);             // value for red channel
  Wire.send(0x00);             // value for blue channel
  Wire.send(0x00);             // value for green channel
  Wire.endTransmission();      // leave I2C bus         // debug - remember to comment out
                                              // before final program run
} 

void loop(){
   // set up I2C on 4 and 5 analog
  Wire.beginTransmission(0x09);// join I2C, talk to BlinkM 0x09
  Wire.send("c");              // ‘c’ == fade to color
  Wire.send(value);             // value for red channel
  Wire.send(value);             // value for blue channel
  Wire.send(value);             // value for green channel
  Wire.endTransmission();      // leave I2C bus         // debug - remember to comment out
// do some stuff here - the joy of interrupts is that they take care of themselves
}

void doEncoder(){
  /* If pinA and pinB are both high or both low, it is spinning
   * forward. If they're different, it's going backward.
   *
   * For more information on speeding up this process, see
   * [Reference/PortManipulation], specifically the PIND register.
   */
  if (digitalRead(encoder0PinA) == digitalRead(encoder0PinB)) {
    encoder0Pos++;
  } else {
    encoder0Pos--;
  }

   if ( encoder0Pos < 0){
     encoder0Pos =  encoder0Pos + 255;
  }
  else if ( encoder0Pos > 255){
     encoder0Pos =  encoder0Pos -255;
  }
  value =  encoder0Pos;
 
}

Same code as before, but this time, the encoder will change the value up, but never down, I have experimented with the interrupt being triggered on HIGH, LOW and CHANGED. No difference.

2

Not sure what the problem might be. However the way encoders are built and used you want the interrupt to be done on RISING, FALLING, or CHANGE. I would stay with RISING until you figure out what other problem might be present. Be sure you also check the wiring for channel going to pin 3. If you put a multimeter on pins 2 and/or 3 and turn the encoder very slow, you should be able to see the high to low to high transition voltage switching from the encoder.

Lefty

3

I managed to avoid the issue by not using any interrupt for the encoder.