AN2579

Theory of operation

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1

Theory of operation

The single click and double click recognition functions featured in the LIS302DL 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 functionality.

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 Chapter 2:

Register description.

The single and double click recognition works independently on the selected output data

rate.

1.1

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 CLICK_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 CLICK_SRC

register is read.

Figure 1.

Single click event with non latched interrupt

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

expired.

(a)

(b)