Application Note

Bosch Sensortec

BlueBox Demo-Board for the digital sensors AN18002

SMB365 (acceleration) and SMD500 (pressure)

•Select any acceleration range [21]

•Select independent interrupt mode [22]

•Put in Hysteresis and Threshold digits for X, Y and Z axis [23]

•Start data acquisition [8]

•accelerate, roll or tilt the TriBox board while watching the interrupt LED [25]

For Interrupt operation as a function of Threshold and Hysteresis the same as shown in chapter

4.3.2before applies with one exception. Threshold and Hysteresis can be selected individually for each axis. For Hysteresis set = Zero, the following logic applies, e.g.:

LED [25] = 1 if LSBX > ThresholdX OR LSBY > ThresholdY OR LSBZ > ThresholdZ LED [25] = 0 if LSBX < ThresholdX AND LSBY < ThresholdY AND LSBZ < ThresholdZ

For Hysteresis set ≠ Zero, the following logic applies, e.g.:

LED [25] = 1 if LSBX > ThresholdX OR LSBY > ThresholdY OR LSBZ > ThresholdZ LED [25] = 0 if LSBX < HysteresisX AND LSBY < HysteresisY AND LSBZ < HysteresisZ

The following example shows how to set up the axis specific Threshold and Hysteresis. The calculation corresponds to the low g operation mode:

Threshold:

20d = 20 ⋅16LSB = 320LSB

∝

20 ⋅ 64mg = 1.28g

Hysteresis:

1d = 320LSB −1⋅ 64LSB = 256LSB

∝

1.28g −1⋅ 256mg = 1.02g

If Hysteresis is equal or above Threshold (LSB values), the interrupt functionality will be disabled. For a total reset of the sensor internal interrupt information just switch to standby mode [20] and continue.

Rev. 1.0

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