Reading gyro values

[Hesher]

Hello guys,

i am working with Pi4J and trying to get some values. Well – so far i get some value and also a reaction if i move the gyro around, but, the value ist the same for all axes x,y,z.
Whats wrong – this output(see code) makes no sense?

//LSM9DS0 Gyro
private static final int GYR_ADDRESS = 0x6A;

//LSM9DS0 Gyro Registers
private static final int CTRL_REG1_G = 0x20;
private static final int CTRL_REG4_G = 0x23;
private static final int OUT_X_L_G = 0x28;
private static final int OUT_X_H_G = 0x29;

private static byte[] bytes = new byte[6];

bus = I2CFactory.getInstance(I2CBus.BUS_1);
device = bus.getDevice(GYR_ADDRESS);
Thread.sleep(250); //Small delay before starting
device.write(CTRL_REG1_G, (byte) 0b00001111); // Normal power mode, all axes enabled
device.write(CTRL_REG4_G, (byte) 0b00110000); // Continuos update, 2000 dps full scale
Thread.sleep(250); //Small delay before starting
while (true) {
int xlg = device.read(OUT_X_L_G, bytes, 0, 6);
if(xlg < 6) {
System.out.println(“Error reading data, < ” + bytes.length + ” bytes”);
}
System.out.println(“X:” + bytes[0] +”~”+ bytes[1] + ” ## Y:” + bytes[2] +”~”+ bytes[3] + ” ## Z:” + bytes[4] +”~”+ bytes[5]);
//output e.g: X:68~68 ## Y:68~68 ## Z:68~68
try {
Thread.sleep(20);
} catch (InterruptedException ex) {
Logger.getLogger(GyroSensor.class.getName()).log(Level.SEVERE, null, ex);
}
}

Thanks a lot for your help!

[Mark Williams]

Hi, are you still having the issue?

does the IMU work with the code from our GIT repo?
https://github.com/mwilliams03/BerryIMU

Mark --OzzMaker.com --

[Hesher]

Hey 🙂

thank you for reply, yes i still have the issue.

The gyro works with C and Phyton code.

PS: i guess i´ve found a bug in python-LSM9DS0-gryo-accel-compass 😉

Line 154 – 156
GYRx = readGYRx()
GYRy = readGYRx()
GYRz = readGYRx()

[Mark Williams]

thanks for pointing the typo out.

I am no Java expert… but your code looks correct to me.

Have you tried reading the values from the compass or accelerometer?

Mark --OzzMaker.com --

[Hesher]

not yet, but i will, just need to fix some other issues with my pi 🙂
i´ll give you an update in some days – if this works / or not

[Hesher]

Hi again,

ive tried to read values from BMP180 – which works well with this code
https://code.google.com/p/raspberry-pi4j-samples/source/browse/AdafruitI2C/src/adafruiti2c/AdafruitBMP180.java?spec=svn74c33e4a5cc3048678061c52c6df0119dbca14a2&r=74c33e4a5cc3048678061c52c6df0119dbca14a2

I´ll try accelerometer next.

[Mark Williams]

cool, once you have it up and running, would you be open to sharing the code with us and I can add it to our GIT repo? under JAVA

Mark --OzzMaker.com --

[Hesher]

Hi,

so here are my findings:

The best lib for the Gyro (L3GD20) i´ve found is:
https://github.com/OlivierLD/raspberry-pi4j-samples/tree/75f8ec4583477a5ee1cf8707e64d9df75976986c/I2C.SPI/src/i2c/sensor

Note: You have to change the ADDRESS in:
L3GD20.java
Line 17: public final static int L3GD20ADDRESS = 0x6b;
to public final static int L3GD20ADDRESS = 0x6a;

And thats the code which works for me – but bugy – if i move the gyro around, it looses accuracy over time

L3GD20 sensor = new L3GD20();
sensor.setPowerMode(L3GD20Dictionaries.NORMAL);
sensor.setFullScaleValue(L3GD20Dictionaries._250_DPS);
sensor.setAxisXEnabled(true);
sensor.setAxisYEnabled(true);
sensor.setAxisZEnabled(true);
sensor.init();
sensor.calibrate();
Thread t = new Thread(){
	
	public void run()
	{
		while (true)
		{      
			try {
				data = sensor.getCalOutValue();
				//data = sensor.getRawOutValues();
			} catch (Exception ex) {
				Logger.getLogger(Raspi.class.getName()).log(Level.SEVERE, null, ex);
			}
			
			now = System.nanoTime();
			timeDelta = (now - lastRead)*0.000000001;
			lastRead = now;
			
			xAngle += (data[0]*timeDelta);
			yAngle += (data[1]*timeDelta);
			zAngle += (data[2]*timeDelta);
			
			
			try { Thread.sleep(1); } catch (InterruptedException ex) {}
		}
	}
};
t.start();
Thread t2 = new Thread(){
	
	public void run()
	{
		while (true)
		{      
			try {
				System.out.println("X:" + Math.round(xAngle) + " ## Y:" + Math.round(yAngle) + " ## Z:" + Math.round(zAngle));
				//System.out.println(timeDelta);
			} catch (Exception ex) {
				Logger.getLogger(Raspi.class.getName()).log(Level.SEVERE, null, ex);
			}
			try { Thread.sleep(500); } catch (InterruptedException ex) {}
		}
	}
};
t2.start();

PS:
Btw: the error in my code above (in my question) is: it reads X-axis only (not x,y,z) 😀

[luizmendesalmeida]

Hi @Hesher.

Did you put BerryIMU working with Pi4J?
If yes, could you share your code?
Thank you in advance.

[Author]

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