Accelerometer IC single/double click event
Accelerometer single and double click events are easiest to understand if one considers them as a tap and double-tap equivalent of what we do with our computer mouse buttons.

The accelerometer MEMS devices that support the feature, incorporate the intelligence to determine when a tap is sensed, or two taps in rapid succession within a set period. The logic also distinguishes between such taps, and vibration due to, for instance, a car's movement. Click / double-click detection also filters out the sharp impact from a device being dropped, for instance, and will not generate a false positive "click" event if this occurs. 

Once such a tap or double-tap event is detected, the accelerometer notifies the host microcontroller of this using either an interrupt line, or normal digital query-response. This saves the programmer from writing reams of code to identify, for instance,


"a pair of brief accelerations in opposing vectors in rapid succession" i.e. a click, 
"two pairs of brief opposing accelerations, with more than x delay between the pairs, and less than y delay between the pairs" i.e. a double-click, and 
"way too many brief accelerations in sequence, so it can't be someone tapping the device twice", i.e. a false alarm. 


This click / double-click detection permits a hand-held device to be used like a single-button computer mouse, as an input interface, with the mouse button clicking being replaced by tapping on the device.