Metawear(gyro)

Mark_L · July 2015

Hey guy,

I want to ask is there an gyro inside the metawear board?(R type), how can I do an android programming to get the pitch angle between the horizontal and metawear(X-axis)?

Thank you!

Eric · July 2015

The current MetaWearR board does not have a gyro.

Mark_L · July 2015

OK, but is it possible to get the angle in another way? thanks Eric

Laura · July 2015

Mark,

The MetaWear RG and the MetaWear RPRO have a gyro on them. The MetaWear R only has an accelerometer.

Please check out these papers for more information on calculating angles using an accelerometer:

http://www.freescale.com/files/sensors/doc/app_note/AN3461.pdf

http://physics.rutgers.edu/~aatish/teach/srr/workshop3.pdf

http://biosport.ucdavis.edu/blog/how-to-calculate-static-lean-and-pitch-angles-from-accelerometer-measurements

Mark_L · July 2015

Hi Laura,

Thanks for your sharing link, it can help me!!,

but before I using it, I need to filter the gravity effect, how can I remove it? is it use the RMS function? and how?

thank you once again.

Eric · July 2015

You can enable high pass filtering to filter out gravity. Documentation about the withHighPassFilter function here.

public void setupAccelerometer(Accelerometer accelCtrllr) {

accelCtrllr.enableXYZSampling().withHighPassFilter((byte) 0)

.withFullScaleRange(SamplingConfig.FullScaleRange.FSR_8G)

.withOutputDataRate(SamplingConfig.OutputDataRate.ODR_100_HZ)

.withSilentMode();

}

Mark_L · July 2015

Hi Eric,

@Override
public void connected() {

    gpioCtrllr= ((GPIO) mwController.getModuleController(Module.GPIO));
    gpioCtrllr.setPinChangeType((byte) 10, GPIO.ChangeType.ANY);
    gpioCtrllr.enablePinChangeNotification((byte) 0);

    accelCtrllr = ((Accelerometer) mwController.getModuleController(Module.ACCELEROMETER));
    accelCtrllr.enableXYZSampling().withHighPassFilter((byte) 0)
            .withFullScaleRange(Accelerometer.SamplingConfig.FullScaleRange.FSR_2G)
            .withOutputDataRate(Accelerometer.SamplingConfig.OutputDataRate.ODR_50_HZ)
            .withSilentMode();

    accelCtrllr.startComponents();

    Toast.makeText(getActivity(), R.string.toast_connected, Toast.LENGTH_SHORT).show();

}

Does like that? but it seems can't filter the gravity.

Eric · July 2015

What is some of the data you are receiving with this accelerometer configuration?

Mark_L · July 2015

sometime nothing but sometime correct..!!

Eric · July 2015

Hrm..are you using the latest API release by chance?

Mark_L · July 2015

Called KITKAT. API 19 4.4.

Mark_L · July 2015

or do you mean the metawear? I am not sure what API I am using, is

compile 'com.mbientlab:metawear:1.8.0'

should I change it to 1.9.3

Eric · July 2015

1.8.0 is sufficient, there isn't anything in 1.9.3 that you would need for what you are doing at the moment.

Also, you cannot configure the accelerometer while it is running. Perhaps the accelerometer is already active when you try to configure it? You can make a call to stopComponents beforehand to ensure the accelerometer is in standby mode prior to configuring it.

Mark_L · July 2015

Ya, that is why, I never stop it when I disconnect, thank you so much.

Mark_L · August 2015

Hi, is it possible to get the xyz acceleration with and without the gravity at the same time? thanks because when it is moving, it seem can't get the pitch angle.

Eric · August 2015

High pass filtering is done on the accelerometer chip. It does not support reporting both filtered and unfiltered data.

Metawear(gyro)

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