LSM303C Datasheet, PDF (21/53 Pages) –

LSM303C
Read #1
Read #n
Figure 7. FIFO multiple read
x,y,z
x,y,z
OUT_X_A
(28-29)
OUT_Y_A
(2A-2B)
OUT_Z_A
(2C-2D)
OUT_X_A
(28-29)
OUT_Y_A
(2A-2B)
OUT_Z_A
(2C-2D)
Functionality
4.3
Activity/Inactivity function
The Activity/Inactivity recognition function allows reducing the power consumption of the
accelerometer block in order to supply other smart applications.
When the Activity/Inactivity recognition function is activated, accelerometer is able to
automatically go to 10 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/to 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
ACT_THS_A register. The high-pass filter is automatically enabled.
Table 9. Activity/Inactivity function control registers
Register
LSB value
ACT_THS_A
Full Scale / 128 [mg]
ACT_DUR_A
8/ODR [s]
When the acceleration becomes smaller than the threshold for at least (8 ACT_DUR
+1)/ODR time, the CTRL_REG1_A (ODR [2:0]) bits of CTRL_REG1_A are bypassed
(Inactivity) and internally set to 10 Hz (ODR [2:0] = 001), but the content of the
CTRL_REG1_A (ODR [2:0]) bits are left untouched.
When the acceleration becomes bigger than the threshold (ACT_THS_A), CTRL_REG1_A
is restored immediately (Activity).
Once the Activity/Inactivity detection function is enabled, it will be applied to the INT_XL pin
by setting the CTRL_REG3_A (INT_XL_INACT) bit to ‘1’.
To disable the Activity/Inactivity detection function, set the content of ACT_THS_A register
to 00h.
4.4
Factory calibration
The IC interface is factory calibrated for sensitivity (LA_So, M_GN), Zero-g level (LA_TyOff)
and Zero-gauss level (M_TyOff).
The trim values are stored inside the device in non-volatile memory. Anytime the device is
turned on, the trim parameters are downloaded into the registers to be used during active
operation. This allows using the device without further calibration.
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