AN4506 datasheet(29/47 Pages) STMICROELECTRONICS

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AN4506

Interrupt generation

DocID026442 Rev 2

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5.5.3

Using the HP filter

The code provided below gives a basic routine which shows the practical use of the wake-

up feature performed on high-pass filtered data. In particular, the device is configured to

recognize when the high-frequency component of the angular rate applied 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

signaled through the use of the INT1 pin.

Write 0Fh into CTRL1

// Turn on the sensor and enable X, Y, and Z

// ODR = 100 Hz

Write 00h into CTRL2

// High-pass filter disabled

Write 80h into CTRL3

// Interrupt driven to INT1 pad

Write 00h into CTRL4

// FS = 245 dps

Write 34h into IG_THS_XH

// Threshold = 100 dps

Write 3Eh into IG_THS_XL

// Threshold = 100 dps

Write 00h into IG_DURATION

// Duration = 0

Write 02h into IG_CFG

// Enable XH interrupt generation

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

// Poll INT1 pin waiting for the

// wake-up event

10 Read IG_SRC

// Return the event that has triggered the

// interrupt

(Wake-up event has occurred; insert

your code here)

// Event handling

12 Go to 8

Write 0Fh into CTRL1

// Turn on the sensor and enable X, Y, and Z

// ODR = 100 Hz

Write 00h into CTRL2

// High-pass filter in Normal mode

Write 80h into CTRL3

// Interrupt driven to INT1 pad

Write 00h into CTRL4

// FS = 245 dps

Write 05h into CTRL5

// Data in DataReg and FIFO are high-pass filtered.

// High-pass-filtered data are used for interrupt

// generation

Write 34h into IG_THS_XH

// Threshold = 100 dps

Write 3Eh into IG_THS_XL

// Threshold = 100 dps

Write 34h into IG_THS_YH

// Threshold = 100 dps

Write 3Eh into IG_THS_YL

// Threshold = 100 dps

10 Write 34h into IG_THS_ZH

// Threshold = 100 dps

Write 3Eh into IG_THS_ZL

// Threshold = 100 dps

12 Write 00h into IG_DURATION

// Duration = 0

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