SCA3000-D01 datasheet(11/43 Pages) VTI

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SCA3000 Series

VTI Technologies Oy

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Doc.Nr. 8257300A.07

Rev.A.07

Acceleration data is not available when the SCA3000 is in motion detection mode

The INT-pin is activated when motion is detected in the X- or Y-axis direction (Z-axis

direction is ignored), see section 2.7 for detailed INT-pin information.

2.4

Free-Fall Detection

2.4.1

Description

During free-fall in the gravitation field, all 3 orthogonal acceleration components are ideally equal to

zero. Due to practical non-idealities, detection must be done using Threshold Level (TL) greater

than 0.

When enabled, the Free-Fall Detection (FFD) will monitor 8 MSB's of the measured acceleration in

the X, Y and Z directions. If the measured acceleration stays within the TL longer than time TFF

(Figure 4 below), which corresponds approx 25 cm drop distance, the FFD will generate an

interrupt to the INT-pin.

+TL

TFF

-TL

Acceleration

X, Y and Z

Time

INT output

"1"

"0"

Figure 4. Free Fall condition.

2.4.2

Usage

Free-fall detection can be enabled by setting FFD_EN bit in MODE register to "1". See section 3.4

for MODE register details.

Acceleration data is available in registers X_LSB, X_MSB, Y_LSB, Y_MSB, Z_LSB, Z_MSB and

BUF_DATA as in measurement mode. See section 3.3 for output register and section 2.7 for

interrupt functionality details.

2.4.3

Example

A simple example of free-fall detection usage:

Write "00010000" (10h) into the MODE register (enable free fall detection, FFD_EN = '1')

Acceleration data can be read normally

INT-pin is activated when free fall is detected, see section 2.7 for detailed INT-pin

information.

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