Help Getting Readings from MiniMU-9 using pi4j

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1

Hi, I am using pi4j to read minimu9 values. However, I don’t understand why the raw values I am getting with my program is so different from using “minimu9-ahrs --mode raw.” Below is my code using java along with outputs from the program and and minimu9-ahrs.

import java.io.IOException;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;
import com.pi4j.io.i2c.I2CBus;
import com.pi4j.io.i2c.I2CDevice;
import com.pi4j.io.i2c.I2CFactory;
import com.pi4j.io.i2c.I2CFactory.UnsupportedBusNumberException;
import com.pi4j.platform.PlatformAlreadyAssignedException;
import com.pi4j.util.Console;


public class pi4j12test {

    /** LSM6DS33 (Gyro and Accelerometer Slave Address 1101011b) */
    public static final char GYRO_ADDR = 0x6b;
    /** LIS3MDL (Magnetometer Slave Address 0011110b) */
    public static final char MAGNETOMETER_ADDR = 0x1e;
    
    public static final char CTRL3_C = 0x12;
    /** CTRL1_XL Linear acceleration sensor control register */
    public static final char CTRL1_XL = 0x10;
    /** CTRL2_G Gyro sensor control register activate from power down*/
    public static final char CTRL2_G = 0x11;
    /** Registers to read Gyro */
    public static final char OUTX_L_G = 0x22;
    /** Registers to read Accelerometer */
    public static final char OUTX_L_XL = 0x28;

    private static void readACC(I2CDevice device) throws InterruptedException, PlatformAlreadyAssignedException, IOException, UnsupportedBusNumberException{
        byte data[] = new byte[6];
        device.read(OUTX_L_XL, data, 0, 6);
        // Format the HIGH/LOW bytes into their respective axis
        int axis[] = new int[3];
        axis[0] = (int)(data[0] | data[1] << 8); // X
        axis[1] = (int)(data[2] | data[3] << 8); // Y
        axis[2] = (int)(data[4] | data[5] << 8); // Z 
        System.out.print("readAccel::axis: " + Arrays.toString(axis) + " ");
    }

    private static void readGyro(I2CDevice device) throws InterruptedException, PlatformAlreadyAssignedException, IOException, UnsupportedBusNumberException{      
        // Read from raw HIGH/LOW bytes gyro registers
        byte data[] = new byte[6];
        device.read(OUTX_L_G, data, 0, 6);
        // Format the HIGH/LOW bytes into their respective axis
        int axis[] = new int[3];
        axis[0] = (int)(data[0] | data[1] << 8); // X
        axis[1] = (int)(data[2] | data[3] << 8); // Y
        axis[2] = (int)(data[4] | data[5] << 8); // Z
        
        System.out.println("readGyro::axis: " + Arrays.toString(axis));
    }

    public static void main(String[] args) throws InterruptedException, PlatformAlreadyAssignedException, IOException, UnsupportedBusNumberException{
        final Console console = new Console();
        console.title("<--Console Output-->");
        console.promptForExit();

        try{
            int [] ids = I2CFactory.getBusIds();
            // console.println("Found following I2C busses: " + Arrays.toString(ids));
        } catch (IOException exception) {
            console.println("I/O error");
        }

        I2CBus i2c = I2CFactory.getInstance(I2CBus.BUS_1);
        I2CDevice device = i2c.getDevice(GYRO_ADDR);
        device.write(CTRL1_XL,(byte)0x50);
        device.write(CTRL2_G,(byte)0x58);
        device.write(CTRL3_C,(byte)0x04);
        
        while(console.isRunning()){
            long lStartTime = System.nanoTime();
            readACC(device);
            readGyro(device);
            long lEndTime = System.nanoTime();
            while((lEndTime - lStartTime)/1000000 < 2000){
                Thread.sleep(100);
                lEndTime = System.nanoTime();
            }
        }
    }

}
PRESS CTRL-C TO EXIT 
readAccel::axis: [-672, -156, -15043] readGyro::axis: [-117, -127, 11385]
readAccel::axis: [-86, -65, -16091] readGyro::axis: [-120, -161, -123]
readAccel::axis: [-72, -68, -16106] readGyro::axis: [-122, -160, -123]
readAccel::axis: [-63, -65, -16119] readGyro::axis: [-121, -160, -121]
readAccel::axis: [-79, -76, -16117] readGyro::axis: [-123, -159, -120]
readAccel::axis: [-69, -95, -16111] readGyro::axis: [-124, -160, -124]
readAccel::axis: [-58, -75, -16103] readGyro::axis: [-121, -161, -124]
readAccel::axis: [-62, -75, -16110] readGyro::axis: [-120, -160, -126]
readAccel::axis: [-79, -75, -16098] readGyro::axis: [-125, -160, -125]
^C

                       GOODBYE                          

pi@raspberrypi:~/java_programs $ minimu9-ahrs --mode raw
  -3604    1629    4322     -133       9   -4022       63     -82     -59
  -3617    1593    4342      -76      48   -4099       43     -84     -62
  -3617    1593    4342     -107      17   -4029       83    -106     -64
  -3617    1593    4342     -137      27   -4043       69     -89     -63
  -3617    1593    4342     -117      25   -4078      105     -95     -65
  -3597    1598    4402     -103      29   -4062       73     -85     -65
  -3597    1598    4402     -150       7   -4064       66     -72     -59
  -3597    1598    4402     -113      16   -4081       73     -88     -63
  -3597    1598    4402     -151     247   -4059       55     -65     -61
  -3589    1570    4340      -78     -10   -4040       52     -96     -70
  -3589    1570    4340     -161       5   -4059       70     -88     -57
  -3589    1570    4340     -100      24   -4020       89    -107     -68
  -3589    1570    4340      -79      17   -4029       66     -90     -62
  -3589    1570    4340     -132      20   -4113       69     -74     -59
  -3600    1584    4328     -137      15   -4079       79     -98     -69
2

Hello.

It looks like you are configuring the LSM6 gyro and accelerometer control registers differently than the minimu-9 ahrs does. In particular, it looks like your full scale range is smaller, so it should make sense that your values are bigger than the values output from minimu9-ahrs --mode raw. You should get identical results if you rewrite your control register commands as:

device.write(CTRL2_G, 0b10001100);  // FS_G = 11 (2000 dps)
device.write(CTRL1_XL, 0b10001100);  // FS_XL = 11 (8 g full scale)

-Jon

3

Thanks, that was it.

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