This post is a follows from an earlier post (iRobot Create 2: Angle Measurement). I have been trying to use the wheel encoders to calculate the angle of the Create 2. I am using an Arduino Uno to interface with the robot.

I use the following code to obtain the encoder values. A serial monitor is used to view the encoder counts.

void updateSensors() {
  Roomba.write(byte(149)); // request encoder counts
  Roomba.write(byte(2));
  Roomba.write(byte(43));
  Roomba.write(byte(44));
  delay(100); // wait for sensors 
  int i=0;
  while(Roomba.available()) {
    sensorbytes[i++] = Roomba.read();  //read values into signed char array
  }
  
  //merge upper and lower bytes
  right_encoder=(int)(sensorbytes[2] << 8)|(int)(sensorbytes[3]&0xFF);
  left_encoder=int((sensorbytes[0] << 8))|(int(sensorbytes[1])&0xFF);

  angle=((right_encoder*72*3.14/508.8)-(left_encoder*72*3.14/508.8))/235;
}

The code above prints out the encoder counts; however, when the wheels are spun backwards, the count increases and will never decrement. Tethered connection to the Create 2 using RealTerm exhibits the same behavior; this suggests that the encoders do not keep track of the direction of the spin. Is this true?

This post is a follows from an earlier post (iRobot Create 2: Angle Measurement). I have been trying to use the wheel encoders to calculate the angle of the Create 2. I am using an Arduino Uno to interface with the robot.

I use the following code to obtain the encoder values. A serial monitor is used to view the encoder counts.

void updateSensors() {
  Roomba.write(byte(149)); // request encoder counts
  Roomba.write(byte(2));
  Roomba.write(byte(43));
  Roomba.write(byte(44));
  delay(100); // wait for sensors 
  int i=0;
  while(Roomba.available()) {
    sensorbytes[i++] = Roomba.read();  //read values into signed char array
  }
  
  //merge upper and lower bytes
  right_encoder=(int)(sensorbytes[2] << 8)|(int)(sensorbytes[3]&0xFF);
  left_encoder=int((sensorbytes[0] << 8))|(int(sensorbytes[1])&0xFF);

  angle=((right_encoder*72*3.14/508.8)-(left_encoder*72*3.14/508.8))/235;
}

The code above prints out the encoder counts; however, when the wheels are spun backwards, the count increases and will never decrement. Tethered connection to the Create 2 using RealTerm exhibits the same behavior; this suggests that the encoders do not keep track of the direction of the spin. Is this true?