Datasheet

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