AN2381 datasheet(42/47 Pages) STMICROELECTRONICS

42 / 47 page

Application information

AN2381

42/47

At step 7, a dummy read at HP_FILTER_RESET register is performed to set the

current/reference acceleration/tilt state against which the device performed the 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.

6.6

Free-Fall detection

This paragraph provides the basics for the use of the free-fall detection feature. In particular

the SW routine that configures the device to detect free-fall events and to signal them is the

following:

read HP_FILTER_RESET register

// Dummy read to force the HP filter to

// actual acceleration value

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

write 6Ah into FF_WU_CFG

// Configure desired wake-up event

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

goto 9

// Poll RDY/INT pin waiting for the

// wake-up event

(Wake-up event has occurred; insert

your code here)

// Event handling

read FF_WU_SRC register

// Return the event that has triggered the

// interrupt

(Insert your code here)

// Event handling

read FF_WU_ACK register

// Clear interrupt request

goto 9

write D7h into CTRL_REG1

// Turn on the sensor and set DF=128

write 08h into CTRL_REG2

// Enables interrupt generation

write 08h into CTRL_REG3

// Set CTRL_REG3 to its default state

write 60h into FF_WU_THS_L register

// Set the lower part of free-fall threshold

write 16h into FF_WU_THS_H register

// Set the higher part of free-fall threshold

write 05h into FF_WU_DURATION

// Set minimum event duration

write D5h into FF_WU_CFG

// Configure free-fall recognition and latch

// interrupt request

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

goto 8

// Poll RDY/INT pin waiting for the free-fall

// event

(Free-fall event has occurred; insert your

code here)

// Event handling

read FF_WU_ACK register

// Clear interrupt request

goto 8

AN2381 Datasheet(PDF) 42 Page - STMicroelectronics

AN2381 Datasheet(HTML) 42 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