A test sketch that logs basic PITCH/ROLL/YAW angle for the KY-521 module.

d1m_MPU6050_pitch_roll_yaw.ini

#include "I2Cdev.h"
#include "MPU6050_6Axis_MotionApps20.h"
#include "Wire.h"

MPU6050 mpu;
uint8_t mpuIntStatus;
uint16_t packetSize;
uint16_t fifoCount;
uint8_t fifoBuffer[64];
Quaternion q;
VectorFloat gravity;
float ypr[3];

volatile bool mpuInterrupt = false;
void dmpDataReady() {mpuInterrupt = true;}

void setup() {
    Wire.begin();
    mpu.initialize();
    mpu.dmpInitialize();
    mpu.setDMPEnabled(true);
    attachInterrupt(0, dmpDataReady, RISING);
    mpuIntStatus = mpu.getIntStatus();
    packetSize = mpu.dmpGetFIFOPacketSize();
    Serial.begin(115200);
}

void loop() {
    while (!mpuInterrupt && fifoCount < packetSize) {}
    mpuInterrupt = false;
    mpuIntStatus = mpu.getIntStatus();
    fifoCount = mpu.getFIFOCount();
    if ((mpuIntStatus & 0x10) || fifoCount == 1024) {
        mpu.resetFIFO();
        Serial.println(F("FIFO overflow!"));
    }
    else if (mpuIntStatus & 0x02) {
        while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
        mpu.getFIFOBytes(fifoBuffer, packetSize);
        fifoCount -= packetSize;
        mpu.dmpGetQuaternion(&q, fifoBuffer);
        mpu.dmpGetGravity(&gravity, &q);
        mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
        Serial.print("ypr\t");
        Serial.print(ypr[0]*180/M_PI);
        Serial.print("\t");
        Serial.print(ypr[1]*180/M_PI);
        Serial.print("\t");
        Serial.print(ypr[2]*180/M_PI);
        Serial.println();
    }
}