Freescale Semiconductor Xtrinsic MAG3110 Magnetometer RD4247MAG3110 RD4247MAG3110 信息指南
产品代码
RD4247MAG3110
MAG3110FAQS
Sensors
4
Freescale Semiconductor
Q: The magnetic data I am reading seems way off from what it used to be. Is the part damaged?
What am I doing wrong?
What am I doing wrong?
A: When exposed to strong magnetic fields, the sensing element may get magnetically contaminated.
MAG3110 has a reset mechanism to get rid of the effects of this exposure. It is recommended that
CTRL_REG2 bit 7 (AUTO_MRST_EN) be set in the initialization routines of your application before
starting to acquire any measurements.
MAG3110 has a reset mechanism to get rid of the effects of this exposure. It is recommended that
CTRL_REG2 bit 7 (AUTO_MRST_EN) be set in the initialization routines of your application before
starting to acquire any measurements.
Q: Can you describe the Active Mode and Standby Mode? What does the TM bit do in
CTRL_REG1?
CTRL_REG1?
A: In Active mode, the device will keep acquiring data continuously according to settings in CTRL_REG1
(CTRL_REG1 = 0bXXXXXX01). In this case (See the next question.) it is possible to synchronize with
the acquisition rate via the INT1 pin.
(CTRL_REG1 = 0bXXXXXX01). In this case (See the next question.) it is possible to synchronize with
the acquisition rate via the INT1 pin.
In Standby mode, the part is in a low-power state and no data acquisition is taking place. The part defaults
to Standby mode upon power-up (AC = TM = 0).
to Standby mode upon power-up (AC = TM = 0).
Set the TM bit when you want the part to acquire only one sample on each axis. See the following table
for details.
for details.
Q: How do I know that new data is ready to be read on a particular axis in Active mode? How can
we synchronize with MAG3110 and minimize overhead I
we synchronize with MAG3110 and minimize overhead I
2
C instructions?
A: The DR register has flags (bits) for indicating if there is new data ready on a particular axis. The user
application can poll these registers to detect new data. However, a more efficient method exists; if any of
the three DR flags (ZDR, YDR, XDR) in CTRL_REG1 is set (by the ASIC upon new data acquisition),
the ZYXDR bit will also be set. INT1 pin logically follows the state of the ZYXDR bit. The user
application can utilize the INT1 pin to synchronize with MAG3110 as follows:
application can poll these registers to detect new data. However, a more efficient method exists; if any of
the three DR flags (ZDR, YDR, XDR) in CTRL_REG1 is set (by the ASIC upon new data acquisition),
the ZYXDR bit will also be set. INT1 pin logically follows the state of the ZYXDR bit. The user
application can utilize the INT1 pin to synchronize with MAG3110 as follows:
1. Put MAG3110 in Active mode (CTRL_REG1 = 0bXXXXXX01).
2. Wait on INT1 to go high.
3. Read at least one MSB from any of the three data registers. (This will clear INT1.)
4. Go back to
Q: How do I clear the interrupt pin / ZYXDR flag?
A: Interrupt pin / ZYXDR is cleared by reading the MSB (most-significant byte) from any one of the three
magnetic data registers.
magnetic data registers.
Q: What are hard-iron effects? How do we compensate for them?
A: Hard-iron effects are magnetic-interference effects that are due to materials which have permanent
magnetism. Such effects can be detected as offset shifts in one or more of the axes and through
mathematical algorithms be compensated for. See above-mentioned application notes for details.
magnetism. Such effects can be detected as offset shifts in one or more of the axes and through
mathematical algorithms be compensated for. See above-mentioned application notes for details.
AC
TM
Description
0
0
ASIC is in low-power standby mode.
0
1
The ASIC shall exit standby mode, perform one measurement cycle based on the programmed
ODR and OSR setting, update the I
ODR and OSR setting, update the I
2
C data registers, and re-enter standby mode.
1
0
The ASIC shall perform continuous measurements based on the current OSR and ODR settings.
1
1
The ASIC shall continue current measurement at fastest applicable ODR for programmed OSR. The
ASIC shall return to programmed ODR after completing the triggered measurement.
ASIC shall return to programmed ODR after completing the triggered measurement.