Theory of operation

AN2579

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1.2

Double click

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

after a first click, a second click is recognized. The recognition of the second click occurs

only if the event satisfies the rules defined by the Latency and Windows registers.

In particular, after the first click has been recognized, the second click detection procedure

is delayed for an interval defined by the Latency register. This means that after the first click

has been recognized, the second click detection procedure will start only if the input

acceleration exceeds the threshold after the Latency window but before the Window has

Once the second click detection procedure is initiated, the second click will be recognized

with the same rule as the first: the acceleration must return below the threshold before the

TimeLimit has expired.

Appropriately defining the Latency window is important to avoid unwanted clicks due to

spurious bouncing of the input signal.

Figure 2.

Single and double click recognition

Figure 2 illustrates a single click event (a) and a double click event (b). The device is able to

distinguish between (a) and (b) by changing the settings of the CLICK_CFG register from

single to double click recognition.

(a)

(b)