Datasheet

BMM150 Geomagnetic Sensor

Page 17

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.

Table 4: Magnetometer advanced self-test control

(0x4C)

Adv.ST <1:0>

Configuration

00b

Normal operation

(no self-test), default

01b

Reserved, do not use

10b

Negative on-chip magnetic

field generation

11b

Positive on-chip magnetic

field generation

The BMM150 API/driver provided by Bosch Sensortec provides a comfortable way to perform

both self-tests and to directly obtain the result without further calculations. It is recommended to

use this as a reference.

4.5 Non-volatile memory

Some of the memory of the BMM150 magnetometer is non-volatile memory (NVM). This NVM is

pre-programmed in Bosch Sensortec fabrication line and cannot be modified afterwards. It

contains trimming data which are required for sensor operation and sensor data compensation,

thus it is read out by the BMM150 API/driver during initialization.

4.6 Magnetometer interrupt controller

Four magnetometer based interrupt engines are integrated in the BMM150: Low-Threshold,

High-Threshold, Overflow and Data Ready (DRDY). Each interrupt can be enabled

independently.

When enabled, an interrupt sets the corresponding status bit in the interrupt status register

(0x4A) when its condition is satisfied.

When the “Interrupt Pin Enable” bit (register 0x4E bit6) is set, any occurring activated interrupts

are flagged on the BMM150’s INT output pin. By default, the interrupt pin is disabled (high-Z

status).

Low-Threshold, High-Threshold and Overflow interrupts are mapped to the INT pin when

enabled, Data Ready (DRDY) interrupt is mapped to the DRDY pin of BMM150 when enabled.

For High- and Low-Threshold interrupts each axis X/Y/Z can be enabled separately for interrupt

detection in the registers “High Int Z en”, “High Int Y en”, “High Int X en”, “Low Int Z en”, “Low Int

Y En” and “Low Int X En” in register 0x4D bit5-bit0. Overflow interrupt is shared for X, Y and Z

axis.

When the “Data Ready Pin En” bit (register 0x4E bit7) is set, the Data Ready (DRDY) interrupt

event is flagged on the BMM150’s DRDY output pin (by default the “Data Ready Pin En” bit is

not set and DRDY pin is in high-Z state).

The interrupt status registers are updated together with writing new data into the magnetic field

data registers. The status bits for Low-/High-Threshold interrupts are located in register 0x4A,

the Data Ready (DRDY) status flag is located at register 0x48 bit0.

If an interrupt is disabled, all active status bits and pins are reset after the next measurement

was performed.