AN4650 datasheet(67/102 Pages) STMICROELECTRONICS

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AN4650

Mode 2 - sensor hub mode

102

6.4.3

Getting compensated magnetometer data

The status of magnetometer data acquisition and hard-iron/soft correction can be checked

using the FUNC_SRC register:



SENSORHUB_END_OP bit is set high when the sensor hub routine is completed. The

acquired magnetometer raw data are available in registers from address 66h

(OUT_MAG_RAW_X_L) to 6Bh (OUT_MAG_RAW_Z_H).



SI_END_OP bit is set high when the execution of the enabled hard-iron and soft-iron

algorithms has completed. If the soft-iron correction is enabled, the magnetometer

uncalibrated data (with soft-iron only applied) are available in registers from address

4Dh (SENSORHUB13_REG) to 52h (SENSORHUB18_REG). The magnetometer

calibrated data, with both hard-iron (if enabled) and soft-iron (if enabled) correction are

available in registers from address 2Eh (SENSORHUB1_REG) to 33h

(SENSORHUB6_REG).

If latch mode is disabled (LIR bit of TAP_CFG is set to 0), the SENSORHUB_END_OP and

SI_END_OP bits are active only for 1/100 Hz, then they are automatically deasserted. If

latch mode is enabled, these two bits are cleared by reading the FUNC_SRC register.

The SENSORHUB_END_OP signal can be driven to the INT1 interrupt pin by setting to 1

the DRDY_ON_INT1 bit of the MASTER_CONFIG register. The SI_END_OP signal can be

driven to the INT2 interrupt pin by setting to 1 the INT2_IRON bit of the MD2_CFG register.

A schematic representation of hard-iron and soft-iron correction feature is illustrated in

Figure 22 below.

If the soft-iron correction is enabled and the soft-iron registers still have the default zero

value, then the magnetometer calibrated data and the magnetometer uncalibrated data will

be equal to zero too. As a consequence, when the soft-iron correction is enabled, the soft-

iron rotation matrix must be at least initialized to the identity matrix multiplied by 8, setting

the value of the MAG_SI_XX, MAG_SI_YY and MAG_SI_ZZ registers to 08h.

Figure 22. Hard-iron / soft-iron correction block scheme

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