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Curie IMU Library

Curie IMU Library

The Curie IMU library enables an Arduino or Genuino 101 to read the output of the on-board IMU
AUTHOR: Arduino
LAST REVISION: 05/16/2023, 09:50 AM

This library is included in the Arc32 core. This core can be installed through the Arduino IDEs , where the package is named "Intel Curie Boards".

The Curie IMU library enables an Arduino or Genuino 101 to read the output of the on-board IMU (Inertial Measurement Unit) containing an accelerometer and a gyroscope and elaborate the raw data coming from it.

To use this library:

1#include <CurieIMU.h>

Examples

Functions

begin()

Description

Initializes the Arduino and Genuino 101 IMU. begin() needs to be called before any other CurieIMU library function.

Syntax

1CurieIMU.begin()

Parameters

none

getGyroRate()

Description

Return the gyro data rate, that is the frequency at which the gyroscope is read.

Syntax

1CurieIMU.getGyroRate()

Returns

The gyro data rate expressed in Hz. Allowed values are:

25, 50, 100, 200, 400, 800, 1600, 3200

setGyroRate()

Description

Defines the output data rate of the gyroscope. The data rate is also the sampling frequency and affects the bandwidth of the readings.

Syntax

1CurieIMU.setGyroRate(int rate)

Parameters

rate: the rate to be set It can assume one of the following values:

25, 50, 100, 200, 400, 800, 1600, 3200

setGyroRange()

Description

Sets the gyro angular measurement range.

Syntax

1CurieIMU.setGyroRange()

Parameters

range: the range to be set.

Allowed values are:

  • 2000 (+/-2000°/s)
  • 1000 (+/-1000°/s)
  • 500 (+/-500°/s)
  • 250 (+/-250°/s)
  • 125 (+/-125°/s)

getAccelerometerRate()

Description

Return the accelerometer data rate, that is the frequency - expressed in Hz - at which the accelerometer is read.

Syntax

1CurieIMU.getAccelerometerRate()

Returns

The accelerometer rate in Hz. Values returned are:

  • 12.5,
  • 25,
  • 50,
  • 100,
  • 200,
  • 400,
  • 800,
  • 1600

setAccelerometerRate()

Description

Defines the output data rate of the accelerometer. The data rate is also the sampling frequency and affects the bandwidth of the readings.

Syntax

1CurieIMU.setAccelerometerRate(float rate)

Parameters

rate: the rate to be set in Hz. Allowed values are:

12.5, 25, 50, 100, 200, 400, 800, 1600

getGyroRange()

Description

Returns the gyro angular measurement range.

Syntax

1CurieIMU.getGyroRange()

Returns

The gyro angular range. Returned values are:

2000 (+/-2000°/s), 1000 (+/-1000°/s), 500 (+/-500°/s), 250 (+/-250°/s), 125 (+/-125°/s)

getAccelerometerRange()

Description

Returns the accelerometer range.

Syntax

1CurieIMU.getAccelerometerRange()

Returns

The accelerometer range expressed as multiples of g. Returned values are:

2 (+/- 2g), 4 (+/- 4g), 8 (+/- 8g), 16 (+/- 16g)

setAccelerometerRange()

Description

Sets the accelerometer range as multiples of g.

Syntax

1CurieIMU.setAccelerometerRange(int range)

Parameters

range: the range to be set expressed as multiples of g. Allowed values are:

2 (+/- 2g), 4 (+/- 4g), 8 (+/- 8g), 16 (+/- 16g)

autoCalibrateGyroOffset()

Description

Starts an autocalibration of the gyro's offset. During this procedure the board should stay motionless. When finished, this procedure writes the proper offset value in the IMU register that can be read with getGyroOffset.

Syntax

1CurieIMU.autoCalibrateGyroOffset()

Parameters

none

autoCalibrateAccelerometerOffset()

Description

Starts an auto-calibration of the accelerometer's offset for the axis specified as argument. This procedure should be executed while the board is kept laying flat and motionless. The offset is stored in the IMU registers and can be read with getAccelerometerOffset.

Syntax

1CurieIMU.autoCalibrateAccelerometerOffset(int, axis, int target)

Parameters

axis: the axis to calibrate. It can assume one of these values:

1X_AXIS 
2Y_AXIS
3Z_AXIS

target: it can be 0 or 1. In particular it has to be used in this way:

1CurieIMU.autoCalibrateAccelerometerOffset(X_AXIS, 0);
2CurieIMU.autoCalibrateAccelerometerOffset(Y_AXIS, 0);
3CurieIMU.autoCalibrateAccelerometerOffset(Z_AXIS, 1);

The target for Z is 1 because it represents the vertical force of gravity (1g) that should be read when the board is laying flat.

noGyroOffset()

Description

Disables the gyro offset.

Syntax

1CurieIMU.noGyroOffset()

Returns

none

noAccelerometerOffset()

Description

Disables the accelerometer offset.

Syntax

1CurieIMU.noAccelerometerOffset()

Returns

none

gyroOffsetEnabled()

Description

Returns the enable state of the gyro offset

Syntax

1CurieIMU.gyroOffsetEnabled()

Returns

true or false if the feature is enabled or disabled

accelerometerOffsetEnabled()

Description

Returns the enable state of the accelerometer offset

Syntax

1CurieIMU.accelerometerOffsetEnabled()

Returns

true or false if the feature is enabled or disabled

getGyroOffset()

Description

Returns the value of gyro's offset.

Syntax

1CurieIMU.getGyroOffset(int axis)

Parameters

axis: the target axis. Can be one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

Returns

The value of the offset for the selected axis. The returned value is from -31.25 °/s to +31.25 °/s in discrete steps of 0.061 °/s.

getAccelerometerOffset()

Description

Returns the value of accelerometer's offset for the selected axis

Syntax

1CurieIMU.getAccelerometerOffset(int axis)

Parameters

axis: the axis of which we want to get the offset value. Can be one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

Returns

The value of the offset for the selected axis. The value returned varies from -495.3 mg to + 495.3 mg in discrete steps of 3.9mg.

setGyroOffset()

Description

Sets the value of gyro offset

Syntax

1CurieIMU.setGyroOffset(int axis, int offset)

Parameters

axis: the target axis. Can be one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

offset: the value of the offset to be set. Valid values are from -31.25 °/s to +31.25 °/s in discrete steps of 0.061 °/s.

setAccelerometerOffset()

Description

Sets the value of accelerometer offset

Syntax

1CurieIMU.setAccelerometerOffset(int axis, int offset)

Parameters

axis: the target axis. Can be one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

offset: The value of the offset for the selected axis. The value goes from -495.3 mg to + 495.3 mg independent of the range selected for the accelerometer; it varies in discrete steps of 3.9mg.

getDetectionThreshold()

Description

Returns the value of the detection threshold

Syntax

1CurieIMU.getDetectionThreshold(int feature)

Parameters

feature: the requested feature. It can assume one of these values:

1CURIE_IMU_FREEFALL
2CURIE_IMU_SHOCK
3CURIE_IMU_MOTION
4CURIE_IMU_ZERO_MOTION
5CURIE_IMU_TAP

setDetectionThreshold()

Description

Sets the value of the detection threshold.

Syntax

1CurieIMU.getDetectionThreshold(int feature, float value)

Parameters

feature: the requested feature. It can assume one of these values:

  • CURIE_IMU_FREEFALL
  • CURIE_IMU_SHOCK
  • CURIE_IMU_MOTION
  • CURIE_IMU_ZERO_MOTION
  • CURIE_IMU_TAP

value: the value to be set, expressed in mg, according to the accelerometer range set, as follows:

CURIE_IMU_FREEFALL

3.91 to 1995.46 mg, in steps of 7.81 mg

CURIE_IMU_SHOCK

2G: 3.91 to 1995.46 mg, in steps of 7.81 mg 4G: 7.81 to 3993.46 mg, in steps of 15.63 mg 8G: 15.63 to 7984.38 mg, in steps of 31.25 mg 16G: 31.25 to 15968.75 mg, in steps of 62.50 mg

CURIE_IMU_MOTION

2G: 0 to 997.05 mg, in steps of 3.91 mg 4G: 0 to 1991.55 mg, in steps of 7.81 mg 8G: 0 to 3985.65 mg, in steps of 15.63 mg 16G: 0 to 7968.75 mg, in steps of 31.25 mg

CURIE_IMU_ZERO_MOTION

2G: 0 to 997.05 mg, in steps of 3.91 mg 4G: 0 to 1991.55 mg, in steps of 7.81 mg 8G: 0 to 3985.65 mg, in steps of 15.63 mg 16G: 0 to 7968.75 mg, in steps of 31.25 mg

CURIE_IMU_TAP

2G: 31.25 to 7968.75 mg, in steps of 62.5 mg 4G: 62.50 to 31937.50 mg, in steps of 125.0 mg 8G: 125.0 to 63875.00 mg, in steps of 250.0 mg 16G: 250.0 to 127750.00 mg, in steps of 500 mg

Returns

The detection threshold of the chosen feature in mg. The range of the returned values is related to the Accelerometer range setting. See setDetectionThreshold for more details.

setDetectionDuration()

Description

Sets the value of the detection duration or waiting window for the selected feature

Syntax

1CurieIMU.setDetectionDuration(int feature, float value)

Parameters

feature: the requested feature. It can assume one of these values:

1CURIE_IMU_FREEFALL
2CURIE_IMU_SHOCK
3CURIE_IMU_MOTION
4CURIE_IMU_ZERO_MOTION
5CURIE_IMU_DOUBLE_TAP
6CURIE_IMU_TAP_SHOCK
7CURIE_IMU_TAP_QUIET

value: the value to be set for each of the features. Some features allow a specific set of values as stated below:

CURIE_IMU_FREEFALL – interval of continuous 0g reading to trigger the interrupt 2.5 to 637.5 ms, in steps of 2.5 ms

CURIE_IMU_SHOCK - The duration of the shock (high-g) condition needed to trigger the interrupt; the sign of high-g must not change during the duration. 50, 75 ms

CURIE_IMU_MOTION - The number of consecutive samples where the threshold value must be exceeded to trigger the interrupt. To get the time correspondent to the samples, divide them by the sampling rate. The value calculated is in seconds. from 1 to 4

CURIE_IMU_ZERO_MOTION - The amount of time where the acceleration read on any of the three axis must stay below the trigger level to activate the interrupt. The value is stored as six bit and is used with a multiplying factor of 1.28, 5.12 or 10.24 seconds. 1.28, 2.56, 3.84, 5.12, 6.40, 7.68, 8.96, 10.24, 11.52, 12.80, 14.08, 15.36, 16.64, 17.92, 19.20, 20.48, 25.60, 30.72, 35.84, 40.96, 46.08, 51.20, 56.32, 61.44, 66.56, 71.68, 76.80, 81.92, 87.04, 92.16, 97.28, 102.40, 112.64, 122.88, 133.12, 143.36, 153.60, 163.84, 174.08, 184.32, 194.56, 204.80, 215.04, 225.28, 235.52, 245.76, 256.00, 266.24, 276.48, 286.72, 296.96, 307.20, 317.44, 327.68, 337.92, 348.16, 358.40, 368.64, 378.88, 389.12, 399.36, 409.60, 419.84, 430.08 S

CURIE_IMU_DOUBLE_TAP – waiting window for the second tap to be read 50, 100, 150, 200, 250, 275, 500, 700 ms

CURIE_IMU_TAP_SHOCK - The time a physical shocking event should happen, exceeding the set threshold, to trigger the interrupt. 50, 75 ms

CURIE_IMU_TAP_QUIET – The time the acceleration reading should stay low to separate two taps. 20, 30 ms

getDetectionDuration()

Description

Returns the value of the detection duration.

Syntax

1CurieIMU.getDetectionDuration(int feature)

Parameter

feature: the requested feature. It can assume one of these values:

  • CURIE_IMU_TAP
  • CURIE_IMU_TAP_QUIET
  • CURIE_IMU_DOUBLE_TAP
  • CURIE_IMU_ZERO_MOTION

Returns

The detection duration of the chosen feature

interrupts()

Description

Enables interrupt for the selected feature.

Syntax

1CurieIMU.interrupts(int feature)

Parameters

feature: the feature for which the interrupt has to be enabled. It can assume one of these values:

1CURIE_IMU_FREEFALL
2CURIE_IMU_SHOCK
3CURIE_IMU_MOTION
4CURIE_IMU_ZERO_MOTION
5CURIE_IMU_STEP
6CURIE_IMU_TAP
7CURIE_IMU_TAP_SHOCK
8CURIE_IMU_TAP_QUIET
9CURIE_IMU_DOUBLE_TAP

noInterrupts()

Description

Disables interrupt for the selected feature.

Syntax

1CurieIMU.noInterrupts(int feature)

Parameters

feature: the feature for which the interrupt has to be disabled. It can assume one of these values:

CURIE_IMU_FREEFALL CURIE_IMU_SHOCK CURIE_IMU_MOTION CURIE_IMU_ZERO_MOTION CURIE_IMU_STEP CURIE_IMU_TAP CURIE_IMU_TAP_SHOCK CURIE_IMU_TAP_QUIET CURIE_IMU_DOUBLE_TAP CURIE_IMU_FIFO_FULL CURIE_IMU_DATA_READY

interruptEnabled()

Description

Return true or false if the interrupt for the selected feature is enabled or not.

Syntax

1CurieIMU.interruptEnabled(int feature)

Parameters

feature: the feature for which the interrupt has to be enabled. It can assume one of these values:

1CURIE_IMU_FREEFALL
2CURIE_IMU_SHOCK
3CURIE_IMU_MOTION
4CURIE_IMU_ZERO_MOTION
5CURIE_IMU_STEP
6CURIE_IMU_TAP
7CURIE_IMU_TAP_SHOCK
8CURIE_IMU_TAP_QUIET
9CURIE_IMU_DOUBLE_TAP
10CURIE_IMU_FIFO_FULL
11CURIE_IMU_DATA_READY

Returns

true or false if the interrupt is enabled or not for the selected feature

getInterruptStatus()

Description

Returns the status of the interrupt for the selected feature.

Syntax

1CurieIMU.getInterruptStatus(int feature)

Parameters

feature: the feature for which the interrupt has to be enabled. It can assume one of these values:

1CURIE_IMU_FREEFALL
2CURIE_IMU_SHOCK
3CURIE_IMU_MOTION
4CURIE_IMU_ZERO_MOTION
5CURIE_IMU_STEP
6CURIE_IMU_TAP
7CURIE_IMU_TAP_SHOCK
8CURIE_IMU_TAP_QUIET
9CURIE_IMU_DOUBLE_TAP
10CURIE_IMU_FIFO_FULL
11CURIE_IMU_DATA_READY

Returns

true or false if an interrupt has been triggered for the selected feature

getStepDetectionMode()

Description

Returns the value of the step detection mode.

Syntax

1CurieIMU.getStepDetectionMode()

Returns

CurieIMUStepMode: the step detection mode. It can assume one of these values:

CURIE_IMU_STEP_MODE_NORMAL CURIE_IMU_STEP_MODE_SENSITIVE CURIE_IMU_STEP_MODE_ROBUST CURIE_IMU_STEP_MODE_UNKNOWN

setStepDetectionMode()

Description

Sets the value of the step detection mode.

Syntax

1CurieIMU.setStepDetectionMode(in mode)

Returns

mode: the step detection mode. It can assume one of these values:

CURIE_IMU_STEP_MODE_NORMAL CURIE_IMU_STEP_MODE_SENSITIVE CURIE_IMU_STEP_MODE_ROBUST CURIE_IMU_STEP_MODE_UNKNOWN

readMotionSensor()

Description

Reads the raw values of the motion sensor (accelerometer + gyro).

Syntax

1CurieIMU.readMotionSensor(int ax, int ay, int az, int gx, int gy, int gz)

Parameters

  • ax: a variable in which the accelerometer's value along x will be stored.
  • ay: a variable in which the accelerometer's value along y will be stored.
  • az: a variable in which the accelerometer's value along z will be stored.
  • gx: a variable in which the gyro's value along x will be stored.
  • gy: a variable in which the gyro's value along y will be stored.
  • gz: a variable in which the gyro's value along z will be stored.

readAccelerometer()

Description

Reads the raw value of the accelerometer.

Syntax

1CurieIMU.readAccelerometer(int ax, int ay, int az)

Parameters

  • ax: a variable in which the accelerometer's value along x will be stored.
  • ay: a variable in which the accelerometer's value along y will be stored.
  • az: a variable in which the accelerometer's value along z will be stored.

To convert the raw value into mg use the following formula: float g = (gRaw/32768.0)*getAccelerometerRange() where gRaw is either ax, ay or az.

readGyro()

Description

Reads the raw value of the gyro.

Syntax

1CurieIMU.readGyro(int gx, int gy, int gz)

Parameters

  • gx: a variable in which the gyro's value along x will be stored.
  • gy: a variable in which the gyro's value along y will be stored.
  • gz: a variablle in which the gyro's value along z will be stored.

To convert any of the raw values in angular velocity (°/s) use the following formula:

1float av = ( avRaw/32768.9)*getGyroRange()

where avRaw is either gx, gy or gz.

readTemperature()

Description

Returns the raw value of the temperature value read by the built-in motion sensor

Syntax

1CurieIMU.readTemperature()

Returns

The value of the read temperature is 16 bit signed. To convert this value you can use the following formula:

1Celsius=(raw/512.0)+23

shockDetected()

Description

Returns true if a shock is detected.

Syntax

1CurieIMU.shockDetected(int axis, int direction)

Parameters

axis: the axis to check for shock detection. It must have one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

direction: the direction to check for shock detection. It must have one of these values:

POSITIVE from zero to positive axis values

NEGATIVE from zero to negative axis values

Returns

true or false if the shock is detected or not on the axis and direction specified.

motionDetected()

Description

Returns true if a motion is detected

Syntax

1CurieIMU.motionDetected(int axis, int direction)

Parameters

axis: the axis to check for motion detection. It must have one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

direction: the direction to check for motion detection. It must have one of these values:

POSITIVE from zero to positive axis values NEGATIVE from zero to negative axis values

Returns

true or false if the motion is detected or not on the axis and direction specified.

tapDetected()

Description

Returns true if a tap is detected

Syntax

1CurieIMU.tapDetected(int axis, int direction)

Parameters

axis: the axis to check for tap detection. It must have one of these values:

1X_AXIS
2Y_AXIS
3Z_AXIS

direction: the direction to check for tap detection. It must have one of these values:

POSITIVE from zero to positive axis values NEGATIVE from zero to negative axis values

Returns

True or false if the tap is detected or not on the axis and direction specified. 

stepsDetected()

Description

Returns true if a step is detected.

Syntax

1CurieIMU.stepsDetected()

Returns

true or false if the step is detected or not.

attachInterrupt()

Description

Attach an interrupt action.

Syntax

1CurieIMU.attachInterrupt(voidFuncPtr callback)

Parameters

callback: The name of the function to be called on interrupt event

detachInterrupt()

Description

Removes an interrupt action.

Syntax

1CurieIMU.detachInterrupt()

Parameters

none

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