AN4506 datasheet(30/47 Pages) STMICROELECTRONICS

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Interrupt generation

AN4506

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DocID026442 Rev 2

At step 13, a dummy read of the REFERENCE register is performed to set the

current/reference angular rate/tilt state against which the device performed the threshold

comparison.

This read may be performed any time it is required to set current rate as a reference state

without waiting for the filter to settle.

5.6

Selective axis movement detection

Selective axis movement detection refers to a specific configuration of IG_CFG and IG_THS

registers that allows the user to recognize when the device is rotating only around the

selected axis.

Referring to Figure 17, a “no rotation zone” is defined around the zero-dps level where the

angular rates are small enough to be considered as zero. It is possible to create a

configuration of the IG_CFG register so that an interrupt is generated only if, i.e., angular

rate for rotation around X and Y axes are around zero, while it is different from zero for the

Z-axis. This means the device is doing a pure yaw rotation.

Figure 17. No-move interrupt

13 Read REFERENCE

// Dummy read to force the HP filter to

// current angular rate value

// (i.e. set reference angular rate)

14 Write 6Ah into IG_CFG

// Enable XH, YH and ZH interrupt generation.

// Interrupt latched

15 Poll INT1 pad; if INT1=0 then go to 8

// Poll INT1 pin waiting for the

// wake-up event

16 Read IG_SRC

// Return the event that has triggered the

// interrupt

(Wake-up event has occurred; insert

your code here)

// Event handling

18 Go to 15

AN4506 датащи(PDF) 30 Page - STMicroelectronics