AN4650 datasheet(51/102 Pages) STMICROELECTRONICS

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AN4650

Android embedded functions

102

Android embedded functions

The LSM6DS3 device implements in hardware the sensor-related functions specified in

Android L; specific IP blocks with negligible power consumption and high-level performance

implement the following functions using only the accelerometer:



Pedometer functions (step detector and step counter);



Significant motion;



Tilt;



Time stamp.

All these functions work at 26 Hz, so the accelerometer ODR must be set at 26 Hz or higher

values.

5.1

Pedometer functions: step detector and step counter

A specific IP block of the LSM6DS3 device is dedicated to pedometer functions: the step

detector and the step counter.

Pedometer functions work at 26 Hz, so the accelerometer ODR must be set at 26 Hz or

higher values.

In order to enable the pedometer functions it is necessary to set to 1 both the FUNC_EN bit

of the CTRL10_C register and the PEDO_EN bit of the TAP_CFG register.

The step detector functionality generates an interrupt every time a step is recognized. In

case of interspersed step sessions, 7 consecutive steps have to be detected before the first

interrupt generation (debounce functionality) in order to avoid false step detections.

This interrupt signal can be driven to the INT1 interrupt pin by setting to 1 the

INT1_STEP_DETECTOR bit of the INT1_CTRL register; it can also be checked by reading

the STEP_DETECTED bit of the FUNC_SRC register.

Instead of generating an interrupt every time a step is recognized, it is possible to generate

it if at least one step is detected within a certain time period. This time period is defined by

setting a value higher than 00h in the STEP_COUNT_DELTA register. It is necessary to set

the TIMER_EN bit of the TAP_CFG register to 1 (to enable the timer) and the TIMER_HR bit

of the WAKE_UP_DUR register to 0 when using this feature: in this case, 1 LSB of the value

of the STEP_COUNT_DELTA register corresponds to 1.6384 seconds. This interrupt signal

can be driven to the INT2 interrupt pin by setting to 1 the INT2_STEP_DELTA bit of the

INT2_CTRL register; it can also be checked by reading the STEP_COUNT_DELTA_IA bit of

the FUNC_SRC register.

The step counter indicates the number of steps detected by the step detector algorithm after

the pedometer function has been enabled. The step count is given by the concatenation of

the STEP_COUNTER_H and STEP_COUNTER_L registers and it is represented as a 16-

bit unsigned number.

The step count is not reset to zero when the accelerometer is configured in Power-Down or

the pedometer is disabled; it can be reset to zero by setting the PEDO_RST_STEP bit of the

CTRL10_C register to 1. After the counter resets, the PEDO_RST_STEP bit is not

automatically set back to 0.

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