CMA3000-D0X VTI Hamlin, CMA3000-D0X Datasheet - Page 10

• Manufacturer Part Number: CMA3000-D0X
• Description: Cma3000-d0x Series 3-axis Accelerometer
• Manufacturer: VTI Hamlin

2.4.3
2.5 Free-Fall Detection
2.5.1
2.5.2
2.5.3
VTI Technologies Oy
www.vti.fi
Example
Description
Usage
Example
Below is a simple example of motion detection usage:
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 the measured acceleration in the X, Y
and Z directions. If all measured XYZ acceleration values stay within the TL longer than time TFF
(Figure 5 below), the FFD will generate an interrupt to the INT-pin. TL can be controlled by FFTHR
[6:0] and TFF by FFTMR [3:0] bits.
Figure 5. Free Fall condition
Free-fall detection can be enabled by setting MODE[2:0] bits in the CTRL register to "101" (sample
rate 100 Hz) or to "110" (sample rate 400 Hz). See section 3.3 for MODE register details.
Acceleration data is available in registers DOUTX, DOUTY and DOUTZ as in measurement mode.
See section 3.3 for output register and section 2.6 for interrupt functionality details.
Below is a simple example of free-fall detection usage:
Acceleration
X, Y and Z
INT output
1. Write "00001000" (08h) into the MODE register (enable motion detection mode, MODE[2:0]
2. Band pass filtered acceleration data at 10 Hz sample rate is available at the output
3. The INT-pin is activated when motion is detected; see section 2.6 for detailed INT-pin
1. Write "00001100" (0Ch) into the MODE register (enable 400 Hz free fall detection mode,
2. Acceleration data can be read normally
3. INT-pin is activated when free fall is detected. See section 2.6 for detailed INT-pin
+TL
-TL
"1"
"0"
bits = '100').
registers.
information.
MODE[2:0] bits = '110').
information.
T1
T1
Doc.Nr. 8281000.12
T2
T2
T3
T3
T4
T4
T5
T5
TFF
T6
T6
T7
T7
T8
T8
Time
Time
CMA3000-D0X Series
Rev. 0.12
10/ 35