LSM303AH Datasheet, PDF (37/82 Pages) –

LSM303AH
Functionality
4.5.1
Note:
4.5.2
Step detector/Step counter
The step detector function generates an interrupt when a step is recognized, the step
counter (automatically enabled when step detector is on) counts the number of the steps
detected.
Step Detector/Step Counter (SD/SC) are enabled by setting to ‘1’-logic the STEP_CNT_ON
bit in the FUNC_CTRL_A (3Fh) register. Additional pedometer advanced configurations can
be used if the FUNC_CFG_EN bit in CTRL2_A (21h) is set to "1". Details of the pedometer
advanced configuration registers are available in Section 9: Advanced configuration register
mapping and Section 10: Advanced configuration registers description.
To disable the pedometer advanced configurations, the FUNC_CFG_EN bit in CTRL2 (3Fh)
must be set to '0'. Refer to Section 10.4: CTRL2_A (3Fh).
The “step detected” interrupt can be read in the FUNC_CK_GATE_A (3Dh) register and by
writing the INT2 STEP DET bit to ‘1’-logic in the CTRL5_A (24h) register it can be routed on
INT2. The number of steps detected can be read from STEP_COUNTER_L_A (3Bh) and
STEP_COUNTER_H_A (3Ch) registers (65535 steps max).
 As default, SD/SC operates with data scaled at 2 g of full scale (device full-scale
independent), but it is possible to make it work with a FS of 4 g by setting the PEDO4g bit
to ‘1’-logic.
 The number of steps can be reset by writing the bit RST nSTEP to ‘1’-logic in
STEP_COUNTER_MINTHS_A (3Ah): this is a synchronous reset activated at the first
data valid and before the algorithm execution. The bit is auto-reset once the counter has
been successfully set to 0000h.
This bit does not reset the algorithm and its variables.
The algorithm and its variables can be reset just by writing the STEP_CNT_ON bit to
‘0’-logic, i.e. turning off the SD/SC routine. The RST PEDO bit in the FUNC_CK_GATE_A
(3Dh) register signals that a SD/SC reset has to be done, so it goes high and remains at
‘1’-logic value until the algorithm ends the reset procedure, which is carried out at first
execution after the SD/SC routine has been re-enabled, before the algorithm starts.
Significant motion
The significant motion functionality can be used in location-based applications in order to
receive a notification indicating when the user is changing location. This function has been
implemented in hardware using only the accelerometer and works at 25 Hz, so the
accelerometer ODR must be set at 25 Hz or higher values.
The significant motion interrupt signal can be driven to the interrupt pin by setting to 1 the
INT2_SIG_MOT bit of the CTRL5_A (24h) register; it can also be checked by reading the
SIG_MOT_DET bit of the FUNC_CK_GATE_A (3Dh) register.
The significant motion function generates an interrupt when the difference between the
number of steps from its initialization is higher or equal than a threshold. The threshold
value corresponds to the number of steps to be performed by the user upon a change of
location before the significant motion interrupt is generated.
The threshold has a default value equal to 6. This threshold is configurable in the
SM_THS_A (34h) register in the advanced configuration registers (refer to Section 9:
Advanced configuration register mapping and Section 10: Advanced configuration registers
description). The significant motion threshold can be used if the FUNC_CFG_EN bit in
CTRL2_A (21h)is set to "1".
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