Datasheet

BMM150 Geomagnetic Sensor

Page 19

BST-BMM150-DS001-01 | Revision 1.0 | April 2013

Bosch Sensortec

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Note: Specifications within this document are subject to change without notice.

4.6.3 Data ready / DRDY interrupt

This interrupt serves for synchronous reading of magnetometer data. It is generated after

storing a new set of values (DATAX, DATAY, DATAZ, RHALL) in the data registers:

Figure 5: Data acquisition and DRDY operation (DRDY in “high active” polarity)

The interrupt mode of the Data Ready (DRDY) interrupt is fixed to non-latched.

It is enabled (disabled) by writing “1” (“0”) to “Data Ready pin En” in register 0x4E bit7.

DRDY pin polarity can be changed by the “DR polarity” bit (register 0x4E bit2), from the default

high active (“1”) to low active (“0”).

4.6.4 Low-threshold interrupt

When the data registers’ (DATAX, DATAY and DATAZ) values drop below the threshold level

defined by the “Low Threshold register (0x4F), the corresponding interrupt status bits for those

axes are set (“Low Int X”, “Low Int Y” and “Low Int Z” in register 0x4A). This is done for each

axis independently. Please note that the X and Y axis value for overflow is -4096. However, no

interrupt is generated on these values. See chapter 4.6.6 for more information on overflow.

Hereby, one bit in “Low Threshold” corresponds to roughly 6µT (not exactly, as the raw

magnetic field values DATAX, DATAY and DATAZ are not temperature compensated).

The Low-threshold interrupt is issued on INT pin when one or more values of the data registers

DATAX, DATAY and DATAZ drop below the threshold level defined by the “Low Threshold”

register (0x4F), and when the axis where the threshold was exceeded is enabled for interrupt

generation:

Result =

(DATAX < “Low Threshold” x 16) AND “Low Int X en” is “0” OR

(DATAY < “Low Threshold” x 16) AND “Low Int Y en” is “0” OR

(DATAZ < “Low Threshold” x 16) AND “Low Int Z en” is “0”

Note: Threshold interrupt enable bits (“Low INT [XYZ] en”) are active low and “1” (disabled) by

default.

Active measurement time

Preset time

Measurement

Data processing

Data write into

output registers

DRDY =

’1 ’

Measurement phase start

Data readout

Measurement

Data processing

Inactive time