Project40.GY521 Module
=========================

Description
------------
The GY-521 module features a 3-axis gyroscope, a 3-axis accelerometer, a digital 
motion processor (DMP), and a temperature sensor.The digital motion processor can 
be used to process complex algorithms directly on the board.


Specification
--------------
- Chip Used: MPU-6050
- Power Supply: 3-5V (internal low-dropout voltage regulator)
- Communication Method: Standard I2C communication protocol
- Built-in 16-bit AD converter, 16-bit data output
- Gyroscope Range: ±250, ±500, ±1000, ±2000 °/s
- Accelerometer Range: ±2, ±4, ±8, ±16g

Connect
--------
+-----------+---------+
| GY-521    | Arduino |
+-----------+---------+
| VCC       | 5V      |
+-----------+---------+
| GND       | GND     |
+-----------+---------+
| SCL       | Pin A5  |
+-----------+---------+
| SDA       | Pin A4  |
+-----------+---------+

.. image:: /img/connect/40_bb.png

Code
-----
.. code-block:: c

    #include "Wire.h" // This library allows you to communicate with I2C devices.

    const int MPU_ADDR = 0x68; // I2C address of the MPU-6050. If AD0 pin is set to HIGH, the I2C address will be 0x69.

    int16_t accelerometer_x, accelerometer_y, accelerometer_z; // variables for accelerometer raw data
    int16_t gyro_x, gyro_y, gyro_z; // variables for gyro raw data
    int16_t temperature; // variables for temperature data

    char tmp_str[7]; // temporary variable used in convert function

    char* convert_int16_to_str(int16_t i) { // converts int16 to string. Moreover, resulting strings will have the same length in the debug monitor.
    sprintf(tmp_str, "%6d", i);
    return tmp_str;
    }

    void setup() {
    Serial.begin(9600);
    Wire.begin();
    Wire.beginTransmission(MPU_ADDR); // Begins a transmission to the I2C slave (GY-521 board)
    Wire.write(0x6B); // PWR_MGMT_1 register
    Wire.write(0); // set to zero (wakes up the MPU-6050)
    Wire.endTransmission(true);
    }
    void loop() {
    Wire.beginTransmission(MPU_ADDR);
    Wire.write(0x3B); // starting with register 0x3B (ACCEL_XOUT_H) [MPU-6000 and MPU-6050 Register Map and Descriptions Revision 4.2, p.40]
    Wire.endTransmission(false); // the parameter indicates that the Arduino will send a restart. As a result, the connection is kept active.
    Wire.requestFrom(MPU_ADDR, 7*2, true); // request a total of 7*2=14 registers
    
    // "Wire.read()<<8 | Wire.read();" means two registers are read and stored in the same variable
    accelerometer_x = Wire.read()<<8 | Wire.read(); // reading registers: 0x3B (ACCEL_XOUT_H) and 0x3C (ACCEL_XOUT_L)
    accelerometer_y = Wire.read()<<8 | Wire.read(); // reading registers: 0x3D (ACCEL_YOUT_H) and 0x3E (ACCEL_YOUT_L)
    accelerometer_z = Wire.read()<<8 | Wire.read(); // reading registers: 0x3F (ACCEL_ZOUT_H) and 0x40 (ACCEL_ZOUT_L)
    gyro_x = Wire.read()<<8 | Wire.read(); // reading registers: 0x43 (GYRO_XOUT_H) and 0x44 (GYRO_XOUT_L)
    gyro_y = Wire.read()<<8 | Wire.read(); // reading registers: 0x45 (GYRO_YOUT_H) and 0x46 (GYRO_YOUT_L)
    gyro_z = Wire.read()<<8 | Wire.read(); // reading registers: 0x47 (GYRO_ZOUT_H) and 0x48 (GYRO_ZOUT_L)
    
    // print out data
    Serial.print("aX = "); Serial.print(convert_int16_to_str(accelerometer_x));
    Serial.print(" | aY = "); Serial.print(convert_int16_to_str(accelerometer_y));
    Serial.print(" | aZ = "); Serial.print(convert_int16_to_str(accelerometer_z));
    // the following equation was taken from the documentation [MPU-6000/MPU-6050 Register Map and Description, p.30]
    Serial.print(" | gX = "); Serial.print(convert_int16_to_str(gyro_x));
    Serial.print(" | gY = "); Serial.print(convert_int16_to_str(gyro_y));
    Serial.print(" | gZ = "); Serial.print(convert_int16_to_str(gyro_z));
    Serial.println();
    
    // delay
    delay(500);
    }

Phenomenon
-----------

.. image:: /img/phenomenon/40.jpg