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I am currently trying to write (obtain) a code for getting raw acceleration values and yaw, pitch and roll angles using these Jeff Rowberg's examples. I have used MPU6050_DMP example to get this code:

// I2Cdev and MPU6050 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"

#include "MPU6050_6Axis_MotionApps20.h"
//#include "MPU6050.h" // not necessary if using MotionApps include file

// Arduino Wire library is required if I2Cdev I2CDEV_ARDUINO_WIRE implementation
// is used in I2Cdev.h
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif

// class default I2C address is 0x68
// specific I2C addresses may be passed as a parameter here
// AD0 low = 0x68 (default for SparkFun breakout and InvenSense evaluation board)
// AD0 high = 0x69
MPU6050 mpu;

//MPU6050 mpu(0x69); // <-- use for AD0 high

// uncomment "OUTPUT_READABLE_YAWPITCHROLL" if you want to see the yaw/
// pitch/roll angles (in degrees) calculated from the quaternions coming
// from the FIFO. Note this also requires gravity vector calculations.
// Also note that yaw/pitch/roll angles suffer from gimbal lock (for
// more info, see: http://en.wikipedia.org/wiki/Gimbal_lock)
#define INTERRUPT_PIN 2  // use pin 2 on Arduino Uno & most boards   
#define LED_PIN 13 // (Arduino is 13, Teensy is 11, Teensy++ is 6)
bool blinkState = false;

// MPU control/status vars
bool dmpReady = false;  // set true if DMP init was successful
uint8_t mpuIntStatus;   // holds actual interrupt status byte from MPU
uint8_t devStatus;      // return status after each device operation (0 =     success, !0 = error)
uint16_t packetSize;    // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount;     // count of all bytes currently in FIFO  
uint8_t fifoBuffer[64]; // FIFO storage buffer

// orientation/motion vars
Quaternion q;           // [w, x, y, z]         quaternion container
VectorInt16 aa;         // [x, y, z]            accel sensor measurements
VectorInt16 aaReal;     // [x, y, z]            gravity-free accel sensor measurements
VectorInt16 aaWorld;    // [x, y, z]            world-frame accel sensor measurements
VectorFloat gravity;    // [x, y, z]            gravity vector
float euler[3];         // [psi, theta, phi]    Euler angle container
float ypr[3];           // [yaw, pitch, roll]   yaw/pitch/roll container and gravity vector

// packet structure for InvenSense teapot demo
uint8_t teapotPacket[14] = { '$', 0x02, 0,0, 0,0, 0,0, 0,0, 0x00, 0x00, '\r', '\n' };

// ================================================================
// ===               INTERRUPT DETECTION ROUTINE                ===
// ================================================================

volatile bool mpuInterrupt = false;     // indicates whether MPU interrupt pin has gone high
void dmpDataReady() {
mpuInterrupt = true;
}

int16_t ax, ay, az, axd, ayd, azd, axo=0, ayo=0, azo=0;

// ================================================================
// ===                      INITIAL SETUP                       ===
// ================================================================

void setup() {
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
    Wire.begin();
    Wire.setClock(400000); // 400kHz I2C clock. Comment this line if having compilation difficulties
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
    Fastwire::setup(400, true);
#endif

// initialize serial communication
// (115200 chosen because it is required for Teapot Demo output, but it's
// really up to you depending on your project)
Serial.begin(38400);
while (!Serial); // wait for Leonardo enumeration, others continue immediately

// NOTE: 8MHz or slower host processors, like the Teensy @ 3.3V or Arduino
// Pro Mini running at 3.3V, cannot handle this baud rate reliably due to
// the baud timing being too misaligned with processor ticks. You must use
// 38400 or slower in these cases, or use some kind of external separate
// crystal solution for the UART timer.

// initialize device
Serial.println(F("Initializing I2C devices..."));
mpu.initialize();
pinMode(INTERRUPT_PIN, INPUT);

// verify connection
Serial.println(F("Testing device connections..."));
Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));

// wait for ready
Serial.println(F("\nSend any character to begin DMP programming and demo: "));
while (Serial.available() && Serial.read()); // empty buffer
while (!Serial.available());                 // wait for data
while (Serial.available() && Serial.read()); // empty buffer again

// load and configure the DMP
Serial.println(F("Initializing DMP..."));
devStatus = mpu.dmpInitialize();

// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1788); // 1688 factory default for my test chip

// make sure it worked (returns 0 if so)
if (devStatus == 0) {
    // turn on the DMP, now that it's ready
    Serial.println(F("Enabling DMP..."));
    mpu.setDMPEnabled(true);

    // enable Arduino interrupt detection
    Serial.println(F("Enabling interrupt detection (Arduino external interrupt 0)..."));
    attachInterrupt(digitalPinToInterrupt(INTERRUPT_PIN), dmpDataReady, RISING);
    mpuIntStatus = mpu.getIntStatus();

    // set our DMP Ready flag so the main loop() function knows it's okay to use it
    Serial.println(F("DMP ready! Waiting for first interrupt..."));
    dmpReady = true;

    // get expected DMP packet size for later comparison
    packetSize = mpu.dmpGetFIFOPacketSize();
} else {
    // ERROR!
    // 1 = initial memory load failed
    // 2 = DMP configuration updates failed
    // (if it's going to break, usually the code will be 1)
    Serial.print(F("DMP Initialization failed (code "));
    Serial.print(devStatus);
    Serial.println(F(")"));
}

// configure LED for output
pinMode(LED_PIN, OUTPUT);
}



// ================================================================
// ===                    MAIN PROGRAM LOOP                     ===
// ================================================================
uint16_t lv = 1;
void loop() {
// if programming failed, don't try to do anything
if (!dmpReady) return;

// wait for MPU interrupt or extra packet(s) available
while (!mpuInterrupt && fifoCount < packetSize) {

}

mpu.getAcceleration(&ax, &ay, &az);

// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();

// get current FIFO count
fifoCount = mpu.getFIFOCount();

// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024) {
    // reset so we can continue cleanly
    mpu.resetFIFO();
    Serial.println(F("FIFO overflow!"));

// otherwise, check for DMP data ready interrupt (this should happen frequently)
} else if (mpuIntStatus & 0x02) {
    // wait for correct available data length, should be a VERY short wait
    while (fifoCount < packetSize) 
    {
      fifoCount = mpu.getFIFOCount();
    }

    // read a packet from FIFO
    mpu.getFIFOBytes(fifoBuffer, packetSize);

    // track FIFO count here in case there is > 1 packet available
    // (this lets us immediately read more without waiting for an interrupt)
    fifoCount -= packetSize;


        // display Euler angles in degrees
        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.print("\t");
        Serial.print("ax ");
        Serial.print(ax);
        Serial.print("\t");
        Serial.print("ay ");
        Serial.print(ay);
        Serial.print("\t");
        Serial.print("az ");
        Serial.println(az);

    // blink LED to indicate activity
    blinkState = !blinkState;
    digitalWrite(LED_PIN, blinkState);
}
if(lv < 501)
++lv;
else
{
  lv = 1;
  digitalWrite(13, !digitalRead(13));
}
}

However when this code, run at 38400 or 1920 baud rate, gives the least frequent FIFO overflow errors (sometimes at 38400, otherwise at 19200). If this code is run below this "optimal" baud rate, FIFO overflow frequency increases. If thic code is run at above "optimal" baud rate, the board freezes after about 10 seconds (always, in every case), the TX just stops binking. Any suggested solution? Board : Arduino Uno, being used with MPU6050

  • Doing a lot of serial printing at a low baud rate will of course cause you to fall behind. You should try to determine where your code gets stuck in the fast case. It looks like you have a possible race condition with potentially clearing the interrupt flag before acting on it, also you do an exact equality comparison on a length that might be able (?) to exceed that. Try putting a counter in your while() loop and printing some output if you are stuck there for a long time. Make sure you aren't overflowing any 16 bit variables... – Chris Stratton Mar 27 '18 at 18:37
  • @ChrisStratton Well, the above code has been modified by me. I have used long instead of int, and I am quite sure that overflow shouldn't be occuring, and used serial printing for debugging. But none of these seemed to help since the board freezes randomly anywhere. There is no pattern. Also, pressing the reset button should restart the code (which happens for other simpler codes), but it's not happening. The board remains frozen.This is the code in case you wanna see it. – virmis_007 Mar 28 '18 at 14:36
  • @ChrisStratton Also, it should not be a case of integer overflow, because I have tested overflow on other simpler programs. In case overflow occurs, the value simply rolls over, it does not freeze the program execution. – virmis_007 Mar 28 '18 at 14:42
  • Again, your best route to a solution is probably going to be figuring out where in the program it does get stuck. – Chris Stratton Mar 28 '18 at 16:18

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