Chief Delphi - 2010 Accelerometer I2C Object/Class

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NerdGuy

26-01-2010 20:36

2010 Accelerometer I2C Object/Class

Hey so we discovered that the 2010 Accelerometer is not Analog it is Completely Digital.

And the Class the Java API provides is for the 2009 Analog Accelerometer.

It even says in the Documentation that they forgot to write a class for the new accelerometer and will try to add it soon.

But Soon isn't soon enough. (Patience Fail)

Does anyone know how to go about extending the I2C class in order to create a valid Accelerometer Class?

This would be unbelievable helpful.
Thx

charrisTTI

26-01-2010 22:54

Re: 2010 Accelerometer I2C Object/Class

I am working on one now. I have a class for an I2C compass which is now working great. Accelerometer is next.

jhersh

27-01-2010 01:26

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by NerdGuy (Post 907485)

It should be trivial to port the C++ version that I posted. http://decibel.ni.com/content/thread/5634

NerdGuy

29-01-2010 22:24

Re: 2010 Accelerometer I2C Object/Class

Thanks,

We converted the code to Java and are going to test it tomorrow.

One thing that we had to change was that instead of using enumerations we used arrays.

This was because the Version of Java the robot is running on does not support the use of enumerations, but i don't see how that could affect the return values.

Again Thanks A Lot!!:)

NerdGuy

01-02-2010 08:54

Re: 2010 Accelerometer I2C Object/Class

I am saddened our ported code did not work.

It may be that we just didnt translate some of the syntax correctly or something else IDK.
Returned 0.0

Heres the code

Quote:

package edu.wpi.first.wpilibj.templates;
import edu.wpi.first.wpilibj.*;

/**
*
* @author ported to Java by Sam Meyer
*
* ADXL345 Accelerometer on I2C.
*
* This class alows access to a Analog Devices ADXL345 3-axis accelerometer on an I2C bus.
* This class assumes the default (not alternate) sensor address of 0x3A (8-bit address).
*/
public class ADXL345 extends SensorBase
{
private static final int kAddress = 0x3A;
private static final int kPowerCtlRegister = 0x2D;
private static final int kDataFormatRegister = 0x31;
private static final int kDataRegister = 0x32;
private static final double kGsPerLSB = 0.004;

/***********************************************
* PowerCtlFields
* *********************************************/
private static final int kPowerCtl_Link = 0x20;
private static final int kPowerCtl_AutoSleep = 0x10;
private static final int kPowerCtl_Measure = 0x08;
private static final int kPowerCtl_Sleep = 0x04;

/***********************************************
* PowerCtlFields
* *********************************************/
private static final int kDataFormat_SelfTest = 0x80;
private static final int kDataFormat_SPI = 0x40;
private static final int kDataFormat_IntInvert = 0x20;
private static final int kDataFormat_FullRes = 0x08;
private static final int kDataFormat_Justify = 0x04;

/***********************************************
* DataFormat_Range
* *********************************************/
private static final int kRange_2G = 0x00;
private static final int kRange_4G = 0x01;
private static final int kRange_8G = 0x02;
private static final int kRange_16G = 0x03;
/***********************************************
* Axes
* *********************************************/
private static final int kAxis_X = 0x00;
private static final int kAxis_Y = 0x02;
private static final int kAxis_Z = 0x04;

/**
* The Default Constructor
* @param slot The slot of the digital module that the sensor is plugged into.
* The default range is 2G (0x00)
*/
public ADXL345(int slot)
{
this(slot, 0x00); // kRange_2G (0x00) is default
}
/**
* Constructor.
*
* @param slot The slot of the digital module that the sensor is plugged into.
* @param range The range (+ or -) that the accelerometer will measure.
*/
public ADXL345(int slot, int range)
{
m_i2c = null;
DigitalModule module = DigitalModule.getInstance(slot);
m_i2c = module.getI2C(kAddress);
m_i2c.write(kPowerCtlRegister, kPowerCtl_Measure);
m_i2c.write(kDataFormatRegister, kDataFormat_FullRes | (int)range);
}

public static final int[] Axes = {0x00, 0x02, 0x04};

private I2C m_i2c;

/**
*
* @param Axis IMPORTANT Axes must be an integer: X = 0x00, Y = 0x02, Z = 0x04
* @return the acceleration in Gs
*/
public double getAcceleration(int Axis)
{
byte[] rawAccel = new byte[2];
m_i2c.read(kDataRegister + (int)Axis, 2, rawAccel);

// Sensor is little endian... swap bytes
byte temp = rawAccel[0];
rawAccel[0] = rawAccel[1];
rawAccel[1] = temp;

int partialAccel = rawAccel[0] * 0x100 + rawAccel[1];
return partialAccel * kGsPerLSB;
}
}

Please if you see any mistakes post them.

Also if we cant get this to work where do you buy the analog accelerometer from last year?

LeelandS

01-02-2010 09:12

Re: 2010 Accelerometer I2C Object/Class

We also attempted a I2C accelerometer port and read 0.0 on x,y, and z.

I think the next step we may take is to flash our crio for C programming and see if we read anything but 0 in that environment.

NerdGuy

01-02-2010 11:17

Re: 2010 Accelerometer I2C Object/Class

Does anyone know if they plan to release a new update for Java with support for an I2C Accelerometer anytime soon.

In the documentation it said that they would release it in later update.

Also in case this never works is it legal to use the analog accelerometer from last year and just use the Accelerometer class in Java that was built for the analog Accelerometer?

jhersh

01-02-2010 13:32

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by NerdGuy (Post 911128)

Does anyone know if they plan to release a new update for Java with support for an I2C Accelerometer anytime soon.

In the documentation it said that they would release it in later update.

I'm not sure if it has been ported to Java or not... I'll check on that.

Quote:

Originally Posted by NerdGuy (Post 911128)

Also in case this never works is it legal to use the analog accelerometer from last year and just use the Accelerometer class in Java that was built for the analog Accelerometer?

Yes, it is legal to use the Accelerometers from last year.

NerdGuy

01-02-2010 15:00

Re: 2010 Accelerometer I2C Object/Class

does anyone know where to buy the Analog Accelerometer Breakout ?

jhersh

01-02-2010 15:17

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by NerdGuy (Post 911236)

does anyone know where to buy the Analog Accelerometer Breakout ?

You can't get the exact board from last year since it was made custom for FIRST... Here is a reasonable replacement: http://www.sparkfun.com/commerce/pro...roducts_id=849

Alternately, you could manufacture your own from the designs posted of last year's boards.

-Joe

charrisTTI

01-02-2010 16:33

Re: 2010 Accelerometer I2C Object/Class

Here is java class for the ADXL345 when connected as I2C device at default address.

Code:

/*----------------------------------------------------------------------------*/

/* Copyright (c) FIRST 2008. All Rights Reserved.                             */

/* Open Source Software - may be modified and shared by FRC teams. The code   */

/* must be accompanied by the FIRST BSD license file in the root directory of */

/* the project.                                                               */

/*----------------------------------------------------------------------------*/



package edu.wpi.first.wpilibj;







/**

 *

 * digital accelerometer from the 2010 KOP

 *

 * this implementation just gets the 3 axis values and allows setting the range

 *

 * Possible enhancements:

 *      Add access to other features of the chip

 *      Add measurement of error during intialization and set channel offsets

 */

public class ADXL345DigitalAccelerometer extends SensorBase {

    private I2C i2c;

    // default address

    private static final byte kAddress = 0x3A;

    // register map from datasheet

    private static final byte OFSX = 0x1E;

    private static final byte OFSY = 0x1F;

    private static final byte OFSZ = 0x20;

    private static final byte BW_RATE = 0x2C;

    private static final byte  POWER_CTL = 0x2D;

    private static final byte DATA_FORMAT = 0x31;

    private static final byte DATAX0 = 0x32;

    private static final byte DATAY0 = 0x34;

    private static final byte DATAZ0 = 0x36;

    private static final byte FIFO_CTL = 0x38;

    private static final byte FIFO_STATUS = 0x39;



    // would use enums here if we had them

    // BW_RATE 0x2C

    private static final byte BW_RATE_R3200B1600 = 0x0F;

    private static final byte BW_RATE_R1600B0800 = 0x0E;

    private static final byte BW_RATE_R0800B0400 = 0x0D;

    private static final byte BW_RATE_R0400B0200 = 0x0C;

    private static final byte BW_RATE_R0200B0100 = 0x0B;

    private static final byte BW_RATE_R0100B0050 = 0x0A;

    private static final byte BW_RATE_R0050B0025 = 0x09;

    private static final byte BW_RATE_R0025B0012 = 0x08;

    private static final byte BW_RATE_R0012B0006 = 0x07;

    private static final byte BW_RATE_R0006B0003 = 0x06;



    private static final byte BW_RATE_LOW_POWER = 0x10;

    

    // POWER_CTL 0x2D

    private static final byte POWER_CTL_LINK = 0x20;

    private static final byte POWER_CTL_AUTO_SLEEP = 0x10;

    private static final byte POWER_CTL_MEASURE = 0x08;

    private static final byte POWER_CTL_SLEEP = 0x04;

    private static final byte POWER_CTL_WAKEUP8 = 0x00;

    private static final byte POWER_CTL_WAKEUP4 = 0x01;

    private static final byte POWER_CTL_WAKEUP2 = 0x02;

    private static final byte POWER_CTL_WAKEUP1 = 0x03;



    // DATA_FORMAT

    public static final byte DATA_FORMAT_02G = 0x00;

    public static final byte DATA_FORMAT_04G = 0x01;

    public static final byte DATA_FORMAT_08G = 0x02;

    public static final byte DATA_FORMAT_16G = 0x03;



    // store the current

    private byte range = DATA_FORMAT_02G;



    public class ADXL345Exception extends RuntimeException {



        /**

         * Create a new exception with the given message

         * @param message the message to pass with the exception

         */

        public ADXL345Exception(String message) {

            super(message);

        }



    }



    //

    // constuctior with slot number parameter

    //

    public ADXL345DigitalAccelerometer(int slot) {

        i2c = new I2C( DigitalModule.getInstance(slot), kAddress );

    }



    // initialize the sensor

    public void intitialize()

    {

        // set BW_RATE

        i2c.write(BW_RATE, BW_RATE_R0100B0050);

        // set POWER_CTL

        i2c.write(POWER_CTL, POWER_CTL_MEASURE);

    }



    // set the range (default is =/- 2g

    public void setRange( byte rangeParam )

    {

        if ( !( rangeParam == DATA_FORMAT_02G ||

                rangeParam == DATA_FORMAT_04G ||

                rangeParam == DATA_FORMAT_08G ||

                rangeParam == DATA_FORMAT_16G ) )

        {

            throw new ADXL345Exception("Invalid range!");

        }





        range = rangeParam;



        i2c.write(DATA_FORMAT, range);

    }



    // get acceleration routines

    public double getXAxis()

    {

        return getAxis( DATAX0 );

    }



    public double getYAxis()

    {

        return getAxis( DATAY0 );

    }



    public double getZAxis()

    {

        return getAxis( DATAZ0 );

    }



    protected double getAxis( byte registerParam )

    {

        // setup array for our data

        byte[] data = new byte[2];

        // read consecutive registers

        this.i2c.read( registerParam, (byte) data.length, data);



        // convert to 2s complement integer

        // [0] has low byte [1] has the high byte

        // jave does not have unsigned so we have to do it this way

        int intResult = ( data[0] & 0xFF ) | ( data[1] << 8 );



        // convert to double based on 10 bit result

        double returnValue = (double)intResult / 512.0 ;



        // now scale based upon our range

        switch( range )

        {

            case DATA_FORMAT_02G:

                returnValue *= 2.0;

                break;

            case DATA_FORMAT_04G:

                returnValue *= 4.0;

                break;

            case DATA_FORMAT_08G:

                returnValue *= 8.0;

                break;

            case DATA_FORMAT_16G:

                returnValue *= 16.0;

                break;

        }

        return returnValue;

    }

}

charrisTTI

01-02-2010 16:35

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by jhersh (Post 911246)

Note, the sparkfun board is 3.3V not 5.0V so you need to order their bidirectional level converter and 3.3V regulator to make it work.

jhersh

01-02-2010 16:48

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by charrisTTI (Post 911302)

Note, the sparkfun board is 3.3V not 5.0V so you need to order their bidirectional level converter and 3.3V regulator to make it work.

From the sparkfun website:

Quote:

Originally Posted by SparkFun

The ADXL320 can be powered from 2.4V-5.25V.

Surely they aren't just giving irrelevant information.

charrisTTI

01-02-2010 17:40

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by jhersh (Post 911317)

From the sparkfun website:

Surely they aren't just giving irrelevant information.

Sorry for the confusion. The ADXL345 (same as this year KOP) from sparkfun is 3.3V.

NerdGuy

01-02-2010 23:49

Re: 2010 Accelerometer I2C Object/Class

RAWR!!!

thanks alot for help.

I will try the above I2C class, looks better than ours.
but then again ours was coded on a hope and a prayer seeing that we did not understand any of that low level stuff.

thanks again.

Also thanks for the analog accel link.

Geek 2.0

03-02-2010 10:27

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by charrisTTI (Post 911300)

Here is java class for the ADXL345 when connected as I2C device at default address.

Code:

/*----------------------------------------------------------------------------*/

/* Copyright (c) FIRST 2008. All Rights Reserved.                             */

/* Open Source Software - may be modified and shared by FRC teams. The code   */

/* must be accompanied by the FIRST BSD license file in the root directory of */

/* the project.                                                               */

/*----------------------------------------------------------------------------*/



package edu.wpi.first.wpilibj;







/**

 *

 * digital accelerometer from the 2010 KOP

 *

 * this implementation just gets the 3 axis values and allows setting the range

 *

 * Possible enhancements:

 *      Add access to other features of the chip

 *      Add measurement of error during intialization and set channel offsets

 */

public class ADXL345DigitalAccelerometer extends SensorBase {

    private I2C i2c;

    // default address

    private static final byte kAddress = 0x3A;

    // register map from datasheet

    private static final byte OFSX = 0x1E;

    private static final byte OFSY = 0x1F;

    private static final byte OFSZ = 0x20;

    private static final byte BW_RATE = 0x2C;

    private static final byte  POWER_CTL = 0x2D;

    private static final byte DATA_FORMAT = 0x31;

    private static final byte DATAX0 = 0x32;

    private static final byte DATAY0 = 0x34;

    private static final byte DATAZ0 = 0x36;

    private static final byte FIFO_CTL = 0x38;

    private static final byte FIFO_STATUS = 0x39;



    // would use enums here if we had them

    // BW_RATE 0x2C

    private static final byte BW_RATE_R3200B1600 = 0x0F;

    private static final byte BW_RATE_R1600B0800 = 0x0E;

    private static final byte BW_RATE_R0800B0400 = 0x0D;

    private static final byte BW_RATE_R0400B0200 = 0x0C;

    private static final byte BW_RATE_R0200B0100 = 0x0B;

    private static final byte BW_RATE_R0100B0050 = 0x0A;

    private static final byte BW_RATE_R0050B0025 = 0x09;

    private static final byte BW_RATE_R0025B0012 = 0x08;

    private static final byte BW_RATE_R0012B0006 = 0x07;

    private static final byte BW_RATE_R0006B0003 = 0x06;



    private static final byte BW_RATE_LOW_POWER = 0x10;

    

    // POWER_CTL 0x2D

    private static final byte POWER_CTL_LINK = 0x20;

    private static final byte POWER_CTL_AUTO_SLEEP = 0x10;

    private static final byte POWER_CTL_MEASURE = 0x08;

    private static final byte POWER_CTL_SLEEP = 0x04;

    private static final byte POWER_CTL_WAKEUP8 = 0x00;

    private static final byte POWER_CTL_WAKEUP4 = 0x01;

    private static final byte POWER_CTL_WAKEUP2 = 0x02;

    private static final byte POWER_CTL_WAKEUP1 = 0x03;



    // DATA_FORMAT

    public static final byte DATA_FORMAT_02G = 0x00;

    public static final byte DATA_FORMAT_04G = 0x01;

    public static final byte DATA_FORMAT_08G = 0x02;

    public static final byte DATA_FORMAT_16G = 0x03;



    // store the current

    private byte range = DATA_FORMAT_02G;



    public class ADXL345Exception extends RuntimeException {



        /**

         * Create a new exception with the given message

         * @param message the message to pass with the exception

         */

        public ADXL345Exception(String message) {

            super(message);

        }



    }



    //

    // constuctior with slot number parameter

    //

    public ADXL345DigitalAccelerometer(int slot) {

        i2c = new I2C( DigitalModule.getInstance(slot), kAddress );

    }



    // initialize the sensor

    public void intitialize()

    {

        // set BW_RATE

        i2c.write(BW_RATE, BW_RATE_R0100B0050);

        // set POWER_CTL

        i2c.write(POWER_CTL, POWER_CTL_MEASURE);

    }



    // set the range (default is =/- 2g

    public void setRange( byte rangeParam )

    {

        if ( !( rangeParam == DATA_FORMAT_02G ||

                rangeParam == DATA_FORMAT_04G ||

                rangeParam == DATA_FORMAT_08G ||

                rangeParam == DATA_FORMAT_16G ) )

        {

            throw new ADXL345Exception("Invalid range!");

        }





        range = rangeParam;



        i2c.write(DATA_FORMAT, range);

    }



    // get acceleration routines

    public double getXAxis()

    {

        return getAxis( DATAX0 );

    }



    public double getYAxis()

    {

        return getAxis( DATAY0 );

    }



    public double getZAxis()

    {

        return getAxis( DATAZ0 );

    }



    protected double getAxis( byte registerParam )

    {

        // setup array for our data

        byte[] data = new byte[2];

        // read consecutive registers

        this.i2c.read( registerParam, (byte) data.length, data);



        // convert to 2s complement integer

        // [0] has low byte [1] has the high byte

        // jave does not have unsigned so we have to do it this way

        int intResult = ( data[0] & 0xFF ) | ( data[1] << 8 );



        // convert to double based on 10 bit result

        double returnValue = (double)intResult / 512.0 ;



        // now scale based upon our range

        switch( range )

        {

            case DATA_FORMAT_02G:

                returnValue *= 2.0;

                break;

            case DATA_FORMAT_04G:

                returnValue *= 4.0;

                break;

            case DATA_FORMAT_08G:

                returnValue *= 8.0;

                break;

            case DATA_FORMAT_16G:

                returnValue *= 16.0;

                break;

        }

        return returnValue;

    }

}

I'm not 100% sure, but by the looks of it (after reading the datasheet), it looks as if you're only taking the least significant byte when reading an axis. Wouldn't that give you a bad number? Again, I'm not sure.

Also, did this code work? I didn't see anything wrong with it.

charrisTTI

03-02-2010 10:46

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by Geek 2.0 (Post 912479)

Code worked fine in my testing.

If you look at the getAxis method you will see that I am doing a 2-byte read when I get the data (2 consecutive registers in one read). This insures that the data does not get corrupted. If two individual 1-byte reads were performed there is a chance that in between the first and second read the data could change. This would result in first read getting the low byte of the prior value and second read getting the high byte of the subsequent value. Putting the two together again could create some really funny numbers. See page 18 of the ADXL345 data sheet "Register 0x32 to Register 0x37" section for more information about this.

Here is an example of the problem: prior value is 0x0100 subsequent value is 0x00ff, a 1 bit change. Two single byte reads would read low byte 0x00 and high byte 0x00 giving 0x0000. No where near close to what the sensor is actually reading.

Geek 2.0

03-02-2010 11:02

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by charrisTTI (Post 912493)

Makes sense. Thanks for the code! Much easier than writing my own.

NerdGuy

03-02-2010 12:49

Re: 2010 Accelerometer I2C Object/Class

/sigh

we tested this code yesterday.

but it did not work for us and since the code seems to work for u guys.
We are probably doing something wrong.

For our wiring we plugged in (obviously 5v to 5v and 0v to ground and so on) but what i have a question on is which I2C channel those plug in to. There are 2 that are not labeled, so i guess the question here is what channel I2C is the kaddress is referring to?

Also I am using the class in the code by

-instantiating with an argument of 4 (which is where the digital module is plugged in to on the crio)

-calling the initialize() method

-and then calling the getXAxis() method in my polling while loop which runs every .02 seconds.

The only thing i could see that might cause a problem is that the accel does not show a significant enough amount of change in the .02s in which we check it.

If this is what is happening please let me know and if its not please try and help.

Thanks in advance.

charrisTTI

03-02-2010 15:28

Re: 2010 Accelerometer I2C Object/Class

Here is my test program:

Code:

public class RobotTest extends SimpleRobot {

    ADXL345DigitalAccelerometer accelerometer = new ADXL345DigitalAccelerometer(4);

    

    public RobotTest()

    {

        accelerometer.intitialize();

        accelerometer.setRange(ADXL345DigitalAccelerometer.DATA_FORMAT_16G);

    }



    /**

     * This function is called once each time the robot enters autonomous mode.

     */

    public void autonomous() {

        

    }



    /**

     * This function is called once each time the robot enters operator control.

     */

    public void operatorControl() {

        this.getWatchdog().setEnabled(false);



        while( this.isOperatorControl() && this.isEnabled() )

        {

            System.out.println("Accel X, Y, Z: " + accelerometer.getXAxis() + " " + accelerometer.getYAxis() + " " + accelerometer.getZAxis() );

            Timer.delay(0.001);

        }

    }

}

Wiring should be from the I2C header on the digital side car. The I2C header is the row of 4 pins directly behind the special Lego RJ12 connector. Wire 5V to 5V, 0V to (-), SDA to SDA, SCL to SCL. Do not use the second row of pins labeled 1,2,3,&4.

Geek 2.0

03-02-2010 15:53

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by charrisTTI (Post 912673)

This is what he means (took me a bit to figure it out without the DSC in front of me, so I thought I'd make a visual aid).

NerdGuy

03-02-2010 16:18

Re: 2010 Accelerometer I2C Object/Class

possibly the most helpful post Ever.

I will try this in about an hour and post the results we were on the ones labeled not these.

Also i am curious what the pins labeled not these are for?
It says "Out" does that just mean those are all Digital Outputs?

Thanks again

jhersh

03-02-2010 16:48

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by NerdGuy (Post 912700)

Also i am curious what the pins labeled not these are for?
It says "Out" does that just mean those are all Digital Outputs?

They are slow digital outputs (kinda like the Spike output channels). We never bothered to add support for them in WPILib, but there is support for them in the FPGA and the FPGA chip object layers. Teams technically could use them, but we don't know why they would.

-Joe

klee17

03-02-2010 17:35

Re: 2010 Accelerometer I2C Object/Class

We tried using the "these" pins instead of the "not these" pins and the accelerometer is returning values now. Thanks for the picture!

Geek 2.0

04-02-2010 08:26

Re: 2010 Accelerometer I2C Object/Class

Okay, I tried it out yesterday and everything seemed to work. Only problem I had was that it floated just enough to make numbers not work for integration to position. For instance, it would float from 0.0 to about 0.007 and then back to 0.0. Problem there is that it technically never had negative acceleration to counter that, meaning the velocity doesn't go back to 0, making my position infinitely change. Even if I do make a dead band, the readings aren't perfectly symmetrical, again meaning velocity doesn't go back to zero. I don't think I'm the only one with this problem. Any suggestions as to how I can use an accelerometer to at least approximate position, accurate enough to maybe 6 inches to a foot, during autonomous?

urg8rb8

04-02-2010 18:57

Re: 2010 Accelerometer I2C Object/Class

We tested out the code for the I2C Accelerometer and we seem to be having some issues. We are doing the following:

Code:

ADXL345DigitalAccelerometer accelerometer;



accelerometer = ADXL345DigitalAccelerometer(4);



accelerometer.initialize();

accelerometer.getZAxis();

For some reason, the code is getting blocked in the initialize() call and never returns out of it. We have the accelerometer plugged into the correct header on the sidecar and we do not have the "blob of solder" on the jumper so we are using the default address that is coded in the class object. What could be the problem?

Any help would be appreciated!

jhersh

05-02-2010 02:28

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by urg8rb8 (Post 913528)

We tested out the code for the I2C Accelerometer and we seem to be having some issues. We are doing the following:

Code:

ADXL345DigitalAccelerometer accelerometer;



accelerometer = ADXL345DigitalAccelerometer(4);



accelerometer.initialize();

accelerometer.getZAxis();

Is your sidecar powered? Is the clock line shorted? Will unplugging the sensor allow the initialize method to return?

charrisTTI

05-02-2010 10:51

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by Geek 2.0 (Post 913128)

One possible improvement would be to calculate and cancel any zero offset error at startup. At a time that you know the robot is not moving and there is no vibration (air compressor off) collect samples from each axis and calculate the average value. Use this as an offset to correct for any zero error on X and Y axis and 1G error on Z axis, assuming "normal" mounting scheme. The chip supports setting offsets for each channel.

urg8rb8

05-02-2010 11:09

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by jhersh (Post 913788)

Is your sidecar powered? Is the clock line shorted? Will unplugging the sensor allow the initialize method to return?

Yes, the sidecar is definitely powered. I am not sure about the clock line being shorted. The clock should be available on the SCL line on the sidecar right? Is it possible that we're missing other hardware modifications or connections? The only thing we've done was connect the 12V supply to the sidecar using the wago connector and the accelerometer to the I2C header.

jhersh

05-02-2010 15:37

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by urg8rb8 (Post 913913)

That should be all you need. And connect it to the NI 9403, of course.

urg8rb8

05-02-2010 15:44

Re: 2010 Accelerometer I2C Object/Class

Quote:

Originally Posted by jhersh (Post 914066)

That should be all you need. And connect it to the NI 9403, of course.

Btw, we tried disconnecting the accelerometer from the I2C bus and initialize() still blocks and never returns. Going to check if there is a clock coming from the sidecar.

spartango

10-02-2010 16:03

Re: 2010 Accelerometer I2C Object/Class

An FYI:

we have this accelerometer working using the code here(thanks much!), and have included it in the latest GRTFramework as well, complete with events for new data, change in data, and data spiking...

If you are curious as to how this works, or interested in using it, visit code.google.com/p/grtframework

http://code.google.com/p/grtframewor...RTADXL345.java
Is where we read data and broadcast/publish events.

saquib

12-02-2011 10:19

Re: 2010 Accelerometer I2C Object/Class

sorry but ive been trying to get my i2c compass to work for a while but its been failing
it says it cant even find the compass
do you think you could help me?

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