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ST/Industrial Sensing Solutions Tap and double-tap: The device can be configured to output an interrupt signal on a dedicated pin when tapped (once or twice) in any direction. The threshold values and the time duration between the two events for the double-tap recognition are configurable. Tilt calculation The accelerometer measures the projection of the gravity vector on the sensing axis. The amplitude of the sensed acceleration changes as the sine of the angle α between the sensitive axis and the horizontal plane. Be- low is shown the basic concept of tilt calculation using an accelerometer (Figure 12). A three-axis linear accelerometer that can sense the vector of gravity along with all three axes X, Y, & Z is needed if the tilting independently from 3D space orientation is required. Trigonometric equations allow the expression of the angle & as a function of acceleration value on the axes X, Y, and Z (Figure 13). The latest sensors offered by ST have the required specifications for an accurate calculation of tilt as these sensors are already factory calibrated, which usually eliminates the need for further calibration in the produc- tion line. However, the calibration of a few parameters of the sensor is recommended to achieve a higher degree of accuracy. These parameters are zero-g level offset, sensitivity accuracy, non-linearity, cross-axis sensitivity, and offset and sensitivity drift over temperature. The latest acceleromters and IMUs from ST have the tilt function embedded in to enable a smooth implemen- tation of the tilt function for a general-purpose of tilt function. The device may be programmed to generate an interrupt when the device's tilt changes by at least 35 degrees since its activation for at least two seconds. The parameters that may get programmed in the embed- ded tilt function are angle threshold that generates inter- rupt event (default 35°), duration of the event, and filter. There are many applications for tilt including factory automation, robotics, building automation, antenna pointing, platform leveling and structural health monitor- ing for position change detection, scales tilt correction, compass tilt correction, (liquid) level sensing tilt correc- tion, construction equipment and man-lift safe operating angle, crane boom angle, and headlight leveling. Pedometer / Step Counter A pedometer is an instrument able to count steps and to estimate walked distance. The pedometer function may Figure 13: Tilt calculation using a 3-axis accelerometer. 16 Figure 14: One-shot mode. Figure 12: Basic concept of tilt calculation using a MEMS accelerometer.

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