ISM303DAC datasheet(33/80 Pages) STMICROELECTRONICS

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ISM303DAC

Functionality

4.2.3

Accelerometer 6D / 4D orientation detection

The ISM303DAC includes 6D / 4D orientation detection which applies only to the

accelerometer.

In this configuration the interrupt is generated when the device is stable in a known

direction. In 4D configuration, detection of the position of the Z-axis is disabled.

4.2.4

Accelerometer activity/inactivity function

The Activity/Inactivity recognition function allows reducing the power consumption of the

system in order to develop new smart applications and is applicable only to the

accelerometer block of the device.

When the Activity/Inactivity recognition function is activated, the ISM303DAC is able to

automatically go to 12.5 Hz sampling rate and to wake up as soon as the interrupt event has

been detected, increasing the output data rate and bandwidth.

With this feature the system may be efficiently switched from low-power mode to full

performance depending on user-selectable positioning and acceleration events, thus

ensuring power saving and flexibility.

The Activity/Inactivity recognition function is activated by writing the desired threshold in the

WAKE_UP_THS_A (33h) register. The high-pass filter is automatically enabled.

If the device is in Sleep (Inactivity) mode, when at least one of the axes exceeds the

threshold in the WAKE_UP_THS_A (33h) the device goes into Sleep-to-Wake (as Wake-

Up).

Activity/Inactivity threshold and duration can be configured in the control registers:

WAKE_UP_THS_A (33h)

WAKE_UP_DUR_A (34h)

4.2.5

Accelerometer self-test

The self-test allows the user to check the sensor functionality without moving it. When the

self-test is enabled, an actuation force is applied to the sensor, simulating a definite input

acceleration. In this case the sensor outputs will exhibit a change in their DC levels which

are related to the selected full scale through the device sensitivity. When the self-test is

activated, the device output level is given by the algebraic sum of the signals produced by

the acceleration acting on the sensor and by the electrostatic test-force. If the output signals

change within the amplitude specified inside Table 3, then the sensor is working properly

and the parameters of the interface chip are within the defined specifications.

The self-test procedure is described in the following figure.

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