FXOS8700 6-Axes Sensor

Get measurement of linear acceleration and magnetic field along the X, Y, and Z axes of the FXOS8700 6-Axes chip

  • Library:
  • Simulink Coder Support Package for NXP FRDM-K64F Board

Description

The FXOS8700 6-Axes Sensor block measures the linear acceleration and the magnetic field along the X, Y, and Z directions. The block has two output ports, Magnet and Accel. The Magnet port outputs the magnetic field from the magnetometer on the FXOS8700 6-Axes chip as a [1x3] vector in uT. The Accel port outputs the acceleration from the accelerometer on the FXOS8700 6-Axes chip as a [1x3] vector in g (9.8 m/s2). The number of output ports vary depending on the active sensors that you select.

Using the parameters of this block, you can change the accelerometer sensitivity by selecting a full-scale range of ±2g, ±4g, or ±8g.

You can also select the Output Data Rates (ODR) for both of the sensors. The Output Data Rates (ODR) for each sensor range from 1.563 Hz to 800 Hz. Interleaved magnetic and acceleration data is available at ODR rates of up to 400 Hz.

Chip Orientation and Axis Orientation Relative to Gravity

Place the board face up on a table, with the dot to the top-right corner of the FXOS8700 6-Axes chip. At this position, the X-axis points away from you, the Y-axis is horizontal and points to the left, and the Z-axis is vertical and points up.

The direction of the arrows shows the positive direction of the reading for the accelerometer and the magnetometer.

When you tilt the board along the X, Y, and Z axes of the chip, this illustration shows the acceleration and the magnetic field.

Acceleration of Gravity in X Direction

Hold the board so that the board faces you and the dot is to the top-right corner of the chip. The acceleration of gravity is static because the chip is stationary.

In the resultant [1x3] vector, the first value that represents the acceleration at the X-axis ≈1 g (9.81 m/s2). The last two values that represent the acceleration at the Y and Z axes (perpendicular to the acceleration of earth gravity) ≈ 0.00 g.

Push the board upward with an acceleration of A m/s2. The acceleration of the gravity is dynamic and equal to the acceleration of the block minus the force of gravity ≈ (+A-9.81) m/s2. In the resultant [1x3] vector, the value of the X-axis ranges between the full-scale range value that you specify in the Acceleration full scale range parameter.

Magnetic Strength in X Direction

Hold the board so that the board faces you and the dot is to the top-right corner of the chip. The magnetometer on the chip measures the earth magnetic field along each sensor axis. In the resultant [1x3] vector, the first value that represents the magnetic strength at the X-axis is minimum.

Ports

Output

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The block has two output ports. The number of ports varies depending on the active sensor that you select in the Active sensor list.

The block outputs the magnetic field as a [1x3] vector. Each value represents the measurement of the magnetic field in μT along the X, Y, and Z axes.

Data Types: double

The block outputs the acceleration as a [1x3] vector. Each value represents the measurement of the acceleration in g (9.8 m/s2) along the X, Y, and Z axes.

Data Types: double

Parameters

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  • Accelerometer only — When you set the Active sensor parameter to Accelerometer only, the block configures an output port. The port on the block is labeled as Accel, indicating that the block outputs the measurement of the acceleration from the accelerometer. The acceleration is measured along the X, Y, and Z axes of the chip.

    The ODR ranges from 1.5625 Hz to 800 Hz.

  • Magnetometer only — When you set the Active sensor parameter to Magnetometer only, the block configures an output port. The port on the block is labeled as Magnet, indicating that the block outputs the measurement of the earth magnetic field from the magnetometer. The magnetic field is measured along the X, Y, and Z axes of the chip.

    The ODR ranges from 1.5625 Hz to 800 Hz.

  • Accelerometer and Magnetometer — When you set the Active sensor parameter to Accelerometer and Magnetometer, the block configures two output ports. The ports on the block are labeled as Magnet and Accel. The Magnet port indicates that the block outputs the measurement of the magnetic field from the magnetometer. The Accel port indicates that the block outputs the measurement of the acceleration from the accelerometer. The acceleration and the magnetic field are measured along the X, Y, and Z axes of the chip.

    The ODR ranges from 0.7813 Hz to 400 Hz.

Specify the rate at which you want the sensors to read the measurement of acceleration and the magnetic field. The values that appear in this parameter vary depending on the active sensor that you select in the Active sensor list.

The accelerometer sensitivity changes with the full scale range that you select in this parameter. Accelerometer sensitivity is 0.244 mg/LSB in 2 g mode, 0.488 mg/LSB in 4 g mode, and 0.976 mg/LSB in 8 g mode. A small, full scale range means that the sensitivity of the sensor is greater, resulting in a more precise reading out of the accelerometer.

Dependencies

This parameter appears when you set the Active sensor parameter to Accelerometer only or Accelerometer and Magnetometer.

By default, the block inherits its sample time based on the context of the block within the model.

See Also

External Websites

Introduced in R2016b