AN4506 datasheet(28/47 Pages) STMICROELECTRONICS

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Interrupt generation

AN4506

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DocID026442 Rev 2

The threshold module which is used by the system to detect any no-move or wake-up event

is defined by the IG_THS registers. The threshold value is expressed over 15 bits as an

unsigned number and is symmetrical around the zero-g level. XH (YH, ZH) is true when the

unsigned angular rate value of the X (Y, Z) channel is higher than IG_THS. Similarly, XL (YL,

ZL) low is true when the unsigned angular rate value of the X (Y, Z) channel is lower than

IG_THS. Refer to Figure 15 for more details.

Figure 15. NM_WU_CFG high and low

5.5.1

Wake-up

Wake-up interrupt refers to a specific configuration of the IG_CFG and IG_THS registers

that allows interrupt generation when the angular rate on the configured axis exceeds a

defined threshold (Figure 16).

Figure 16. Wake-up interrupt

5.5.2

HP filter bypassed

This paragraph provides a basic algorithm which shows the practical use of the wake-up

feature. In particular, with the code below, the device is configured to recognize when the

absolute angular rate along either the X-, Y-, or Z-axis exceeds a preset threshold (100 dps

is used in the example). The event which triggers the interrupt is latched inside the device

and its occurrence is signalled through the use of the INT1 pin.

0 dps

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