MMA8652FC 3-Axis Accelerometer

Get measurement of linear acceleration along the X, Y, and Z axes of the MMA8652FC 3-Axis chip

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Libraries:
Simulink Coder Support Package for BBC micro:bit/Accelerometer

Description

The MMA8652FC 3-Axis Accelerometer block measures the linear acceleration along the X, Y, and Z axes. The block has one output port, Accel. The Accel port outputs the acceleration from the as a [1x3] vector in g (9.8 m/s2).

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

You can also select the Output Data Rates (ODR) for both of the sensors. The Output Data Rates (ODR) ranges from 1.5625 Hz to 800 Hz.

Chip Orientation and Axis Orientation Relative to Gravity

Hold the board so that the board faces you and the line to the top of the MMA8652FC 3-Axis chip is aligned horizontally to the table. At this position, the X-axis is horizontal and points to the left, the Y-axis is vertical and points down, and the Z-axis points towards you.

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

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

Acceleration of Gravity in X Direction

Hold the board so that the board faces you and the line to the right of the chip is aligned vertically to the table. 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.

Ports

Output

The block has one output port.

Accel — Acceleration applied to the sensor along each axis of the chip

vector

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

Sensor output data rate (ODR) — Rate at which data is sampled

800Hz (default) | 400Hz | 200Hz | 100Hz | 50Hz | 12.5Hz | 6.25Hz | 1.5625Hz

Specify the rate at which you want the accelerometer to read the measurement of acceleration.

Acceleration full scale range — Range of acceleration deviation that the accelerometer can measure

-4g to +4g (default) | -2g to +2g | -8g to +8g

Accelerometer sensitivity is 256 counts/g in 2 g mode, 128counts/g in 4 g mode, and 64counts/g in 8 g mode. A small, full scale range means that the sensor sensitivity is heightened, resulting in a more precise reading from the accelerometer.

Sample time — Specify how often the block reads data from the accelerometer on the chip

0.1 (default)

When you specify this parameter as-1, Simulink® determines the best sample time for the block based on the block context within the model.