AN2381 datasheet(43/47 Pages) STMICROELECTRONICS

43 / 47 page

AN2381

Application information

43/47

The code sample exploits a threshold set at 350mg for free-fall recognition and the event is

notified by the hardware signal RDY/INT. At step 6, the FF_WU_DURATION register is

configured so to ignore events that are shorter than 5/DR=5/160~30msec (DR=data rate;

see Table 7.) in order to avoid false detections.

Once the free-fall event has occurred, a dummy read at FF_WU_ACK reg clears the request

and the device is ready to recognize other events.

6.7

Direction detection

The code disclosed below illustrates the ability of the LIS3LV02DL device to recognize in

which direction it has been tilted and to flag a change in its orientation/tilt with respect to the

previous state through the hardware RDY/INT signal. In the example below the device is

configured to detect tilt which exceed 260mg (set as external/outer threshold), while the

internal/inner threshold is set, as an example, to 150mg.

At step 8, a dummy read at HP_FILTER_RESET register is performed to set the current

acceleration/tilt as a reference state value for threshold comparison. This read may be

performed any time it is required to set the orientation/tilt of the device as a reference state

without waiting for the filter to settle.

write C7h into CTRL_REG1

// Turn on the sensor and set DF=512

write 08h into CTRL_REG2

// Enables interrupt generation

write 4Bh into CTRL_REG3

// Enable the HP filter and force HPc=4096

write A3h into DD_THSE_L register

// Set the lower part of outer threshold

write 10h into DD_THSE_H register

// Set the higher part of outer threshold

write 99h into DD_THSI_L register

// Set the lower part of inner threshold

write 09h into DD_THSI_H register

// Set the higher part of inner threshold

read HP_FILTER_RESET register

// Dummy read to force the HP filter to

// actual acceleration value

// (i.e. set reference acceleration/tilt value)

write CFh into DD_CFG register

// Configure direction detection along

// X and Y axes

poll RDY/INT pad; if RDY/INT=0 then

goto 10

// Poll RDY/INT pin waiting for a direction

// change event

(Direction/tilt has changed; insert your

code here)

// Event handling

read DD_SRC register

// Return the direction in which the tilt

// has occurred

(Insert your code here)

// Event handling

read DD_ACK register

// Clear interrupt request (on direction

// change)

goto 10

AN2381 Datasheet(PDF) 43 Page - STMicroelectronics

AN2381 Datasheet(HTML) 43 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Datasheet Download

Link URL