AN3308 datasheet(30/52 Pages) STMICROELECTRONICS

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Click and double click recognition

AN3308

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Doc ID 18198 Rev 1

Click and double click recognition

The single click and double click recognition functions featured in the LIS3DH help to create

a man-machine interface with little software loading. The device can be configured to output

an interrupt signal on a dedicated pin when tapped in any direction.

If the sensor is exposed to a single input stimulus, it generates an interrupt request on

inertial interrupt pin INT1 and/or INT2. A more advanced feature allows the generation of an

interrupt request when a double input stimulus with programmable time between the two

events is recognized, enabling a mouse button-like function.

This function can be fully programmed by the user in terms of expected amplitude and

timing of the stimuli by means of the dedicated set of registers described in Section 8.3.

Single and double click recognition works independently on the selected output data rate.

8.1

Single click

If the device is configured for single click event detection, an interrupt is generated when the

input acceleration on the selected channel exceeds the programmed threshold, and returns

below it within a time window defined by the TimeLimit register.

If the LIR bit of the TAP_CFG register is not set, the interrupt is kept high for the duration of

the latency window. If the LIR bit is set, the interrupt is kept high until the TAP_SRC register

is read.

Figure 14.

Single click event with non latched interrupt

In Figure 14(a) the click has been recognized, while in Figure 14(b) the click has not been

recognized because the acceleration goes under the threshold after the TimeLimit has

expired.

(a)

(b)

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