AN4650 datasheet(41/102 Pages) STMICROELECTRONICS

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AN4650

Interrupt generation

102

The example code which implements the SW routine for the wake-up event recognition

using the slope filter is given below.

Since the duration time is set to zero, the wake-up interrupt signal is generated for each

X,Y,Z slope data exceeding the configured threshold. The WK_THS field of the

WAKE_UP_THS register is set to 000010b, therefore the wake-up threshold is 62.5 mg

(= 2 * FS_XL / 26).

4.4

6D/4D orientation detection

The LSM6DS3 device provides the capability to detect the orientation of the device in

space, enabling easy implementation of energy-saving procedures and automatic image

rotation for mobile devices.

4.4.1

6D orientation detection

Six orientations of the device in space can be detected; the interrupt signal is asserted when

the device switches from one orientation to another. The interrupt is not re-asserted as long

as the position is maintained.

6D interrupt is generated when, for two consecutive samples, only one axis exceeds a

selected threshold and the acceleration values measured from the other two axes are lower

than the threshold: the ZH, ZL, YH, YL, XH, XL bits of the D6D_SRC (1Dh) register indicate

which axis has triggered the 6D event.

In more detail:



D6D_IA is set high when the device switches from one orientation to another.



ZH (YH, XH) is set high when the face perpendicular to the Z(Y,X) axis is almost flat

and the acceleration measured on the Z(Y,X) axis is positive and in the module bigger

than the threshold.



ZL (YL, XL) is set high when the face perpendicular to the Z(Y,X) axis is almost flat and

the acceleration measured on the Z(Y,X) axis is negative and in the module bigger than

the threshold.

The SIXD_THS[1:0] bits of the TAP_THS_6D register are used to select the threshold value

used to detect the change in device orientation. The threshold values given in Table 30 are

valid for each accelerometer full-scale value.

Write 60h into CTRL1_XL

// Turn on the accelerometer

// ODR_XL = 416 Hz, FS_XL = 2g

Write 00h into TAP_CFG

// Apply slope filter; latch mode disabled

Write 00h into WAKE_UP_DUR

// No duration

Write 02h into WAKE_UP_THS

// Set wake-up threshold

Write 20h into MD1_CFG

// Wake-up interrupt driven to INT1 pin

Table 29. D6D_SRC register

D6D_IA

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