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Gyro (IMU)

Overview

The component Gyro Accelerometer Compass provides a 9-axis Motion Processing Unit in form of a MPU9250. The component is controll via I2C protocol.

Example

A sample project for the Arduino IDE is provided in Gyro.ino which could be downloaded here

Activating the component

The component has a dip switch SW310 for activating the component. Each of the five buttons is connected to one IO port. Switch 1 is not connected and therefore the state of this switch is not relevant. The buttons are connected to the following ports

Function SWITCH IO port Conflicts with Remarks
INT 1 14 mikroBus, SW404-2, INT; Camera, SW402-4, D2; SD Card, SW406-5, CLK; Grove Digital2, SW207-1, IO14
AD0/SD0 2 12 RFID, SW303-2, IRQ; mikroBus, SW404-1, PWM; Camera, SW402-3, D1; SD Card, SW406-2, DAT2; Grove Digital1, SW206-1, IO12
SDA/SDI 3 19 RFID, SW303-3, MISO; OLED, SW309-2, SDA; TFT, SW314-1, MISO; mikroBus, SW405-2, MISO; Unit-Bus, SW200-2, CN212 - PIN5; Grove I2C, SW203-1, I2C-SDA I2C Pull-up by SW307
SCL/SCLK 4 4 OLED, SW309-1, SCL; Camera, SW402-1, RCK/RCKL; SD Card, SW406-3, DAT1; Unit-Bus, SW200-1, CN212 - PIN 6; Grove I2C, SW203-2, I2C - SCL I2C Pull-up by SW308

Using the component

It's very important to switch on SW401.

First you should define two constants for the two I2C signal lines: SDA (serial data) and SCL (serial clock):

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#define SDA 19
#define SCL 4

Additionally constants for the addresses of the IMU component are recommended:

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#define    MPU9250_ADDRESS            0x68
#define    MAG_ADDRESS                0x0C

#define    GYRO_FULL_SCALE_250_DPS    0x00
#define    GYRO_FULL_SCALE_500_DPS    0x08
#define    GYRO_FULL_SCALE_1000_DPS   0x10
#define    GYRO_FULL_SCALE_2000_DPS   0x18

#define    ACC_FULL_SCALE_2_G        0x00
#define    ACC_FULL_SCALE_4_G        0x08
#define    ACC_FULL_SCALE_8_G        0x10
#define    ACC_FULL_SCALE_16_G       0x18

With two utility functions (defined in the sample project Gyro.ino) data is read and write from the I2C bus. With these functions the component is configured in the setup method:

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void setup()
{
    // Arduino initializations
    Wire.begin(SDA,SCL);
    Serial.begin(115200);

    // Set accelerometers low pass filter at 5Hz
    I2CwriteByte(MPU9250_ADDRESS,29,0x06);
    // Set gyroscope low pass filter at 5Hz
    I2CwriteByte(MPU9250_ADDRESS,26,0x06);


    // Configure gyroscope range
    I2CwriteByte(MPU9250_ADDRESS,27,GYRO_FULL_SCALE_1000_DPS);
    // Configure accelerometers range
    I2CwriteByte(MPU9250_ADDRESS,28,ACC_FULL_SCALE_4_G);
    // Set by pass mode for the magnetometers
    I2CwriteByte(MPU9250_ADDRESS,0x37,0x02);

    // Request continuous magnetometer measurements in 16 bits
    I2CwriteByte(MAG_ADDRESS,0x0A,0x16);

    // Store initial time
    ti = millis();

    Serial.println("MPU9250");
}

In the loop method you could access the three IMU components.

Accelerometer

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 int16_t ax = -(Buf[0]<<8 | Buf[1]);
 int16_t ay = -(Buf[2]<<8 | Buf[3]);
 int16_t az = Buf[4]<<8 | Buf[5];
Gyroscope
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int16_t gx = -(Buf[8]<<8 | Buf[9]);
int16_t gy = -(Buf[10]<<8 | Buf[11]);
int16_t gz = Buf[12]<<8 | Buf[13];

Magnetometer

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uint8_t ST1;
do
{
    I2Cread(MAG_ADDRESS,0x02,1,&ST1);
}
while (!(ST1&0x01));

// Read magnetometer data
uint8_t Mag[7];
I2Cread(MAG_ADDRESS,0x03,7,Mag);


// Create 16 bits values from 8 bits data

// Magnetometer
int16_t mx = -(Mag[3]<<8 | Mag[2]);
int16_t my = -(Mag[1]<<8 | Mag[0]);
int16_t mz = -(Mag[5]<<8 | Mag[4]);

Sample project

A sample project for the Arduino IDE is provided in Gyro.ino which could be downloaded here