Information

BMA280
Data sheet
Page 31
BST-BMA280-DS000-11 | Revision 1.8 | August 2014 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
4.7.6 Tap sensing
Tap sensing has a functional similarity with a common laptop touch-pad or clicking keys of a
computer mouse. A tap event is detected if a pre-defined slope of the acceleration of at least
one axis is exceeded. Two different tap events are distinguished: A ‘single tap’ is a single event
within a certain time, followed by a certain quiet time. A ‘double tap’ consists of a first such
event followed by a second event within a defined time frame.
Single tap interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) s_tap_en. Double tap
interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) d_tap_en.
While temporary latching is used do not simultaneously enable single tap interrupt and double
tap interrupt.
The status of the single tap interrupt is stored in bit (0x09) s_tap_int, the status of the double
tap interrupt is stored in bit (0x09) d_tap_int.
The slope threshold for detecting a tap event is set by bits (0x2B) tap_th. The meaning of
(0x2B) tap_th depends on the range setting. 1 LSB of (0x2B) tap_th corresponds to a slope of
62.5mg in 2g-range, 125mg in 4g-range, 250mg in 8g-range, and 500mg in 16g-range.
In figure 8 the meaning of the different timing parameters is visualized:
tap_shock tap_quiet tap_dur
tap_shock tap_quiet
time
12.5 ms
single tap detection
double tap detection
slope
time
12.5 ms
time
1st tap 2nd tap
tap_th
Figure 8: Timing of tap detection