Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 45 / - proprietary information - 06 March 2009
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Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.
7.9.7.3 Tap sensing interrupt: algorithm
An acceleration slope is detected when the criterion tapsens_th_criteria is set.
The tap sensing feature is using two acceleration signal slope detections. The first slope
detection sets the status bit first_tapsens_s to ‘1’. An interrupt signal is generated only if new
slope detection comes after tapsens_shock = (120*Tupdate) = 50ms and before tapsens_dur.
first_tapsens is reset when at least one of the following conditions is true:
• tap sensing feature is disabled during the processing of tap sensing sequence.
• tapsens_dur period is passing.
• tap sensing interrupt occurs.
The sign of the slope, which has initiated the interrupt signal, is stored in the flag bit
tapsens_sign_int_* , only if the corresponding enable bit tapsens_int_* is set.
Tap sensing function is defined with an OR condition. For example, if all axes are selected
(tapsens_int_x= tapsens_int_y= tapsens_int_z=’1’), the procedure could start with a pulse on
the X-axis and finish with a pulse on the Z-axis.
The procedure starts always with the first detected pulse.
acceleration
tiptap_dur
tiptap_shock
INT
High slope detection within
tiptap_shock
Æ No interrupt generated
High slope detection within
tiptap_dur
Æ interrupt generated
High slope detection
Æ start
Figure 9: example of tap sensing detection with use of tapsens_th, tapsens_dur