MC3253 Datasheet, PDF (30/72 Pages) List of Unclassifed Manufacturers – Axis Accelerometer

MC3253 3-Axis Accelerometer
Preliminary Datasheet
9.4 SHAKE DETECTION
The threshold for detecting a shake event can be set to a range of values around a 1.3g
baseline. The shake threshold can range from 0.925g to 1.672g. The value is a signed, 2’s
complement number. Resolution is approximately 2.9mg/bit.
A shake event will be triggered when high-g values are sensed for a sufficient number of
samples.
SHDB: Shake Debounce Register can be set to count from 1 to 63 events before setting the
SHAKED bit in the TILT: Status Register. Higher values yield longer evaluation periods. See
Figure 12 and Figure 13.
Shake detection can be any combination of axes. To enable detection even when not using
interrupts, set the corresponding SHINTX, SHINTY, or SHINTZ bit-fields in the INTEN:
Interrupt Enable Register.
Event
X Axis
Y Axis
Shake |X| > +1.3g ± Threshold or
|Y| > +1.3g ±
Threshold
Table 20. SHAKE Event Evaluation (Baseline + Offset)
Z Axis
or |Z| > +1.3g± Threshold
Sensed g value
{ SHAKE_TH
Register
1.3 g
Sample
Shake detect is reset here
Time
Shake Debounce Register == 4 but the sensed g value is above 1.3g
+ SHAKE_TH for only 3 samples. Shake event is not detected.
Figure 12. Example Use of Shake Detection Hardware – Shake Not Detected
mCube Proprietary.
APS-048-0026v1.2
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