6.5 Si7210 Hall-Effect Sensor
The Si7210 family of hall effect sensors from Silicon Labs combines a chopper-stabilized hall element with a low-noise analog amplifier,
13-bit analog-to-digital converter, and an I
2
C interface. Leveraging Silicon Labs' proven CMOS design techniques, the Si7210 family
incorporates digital signal processing to provide precise compensation for temperature and offset drift.
The 13-bit magnetic field strength can be read through the I
2
C interface at any time. The Si7210 also features an output pin which can
provide a digital alert when the measured field is above or below a programmable threshold value.
Applications for the Si7210 include mechanical position sensing in consumer, industrial and automotive applications, reed switch re-
placement, fluid level measurement, speed sensing and control knobs and switches.
The I
2
C bus used for the Si7210 is shared with the Si7021 relative humidity and temperature sensor. To use the sensor, PB3 must be
set high, which also powers the Si7021. When enabled, the sensors' current consumption is included in the AEM measurements.
SENSOR_ENABLE
PI4 (I2C2_SDA #7)
PI5 (I2C2_SCL #7)
PB3 (GPIO)
SENSOR_I2C_SDA
SENSOR_I2C_SCL
VDD
EFM32
Hall-Effect
Sensor
Si7210
PB0 (GPIO)
SENSOR_HALL_VOUT
Figure 6.5. Si7210 Hall-Effect Sensor
Please refer to the Si7210 datasheet for more information.
6.6 LC Sensor
In the bottom right corner of the board there is an inductive-capacitive sensor for demonstrating the low energy sensor interface (LE-
SENSE). The LESENSE peripheral uses the voltage digital-to-analog converter (VDAC) to set up an oscillating current through the in-
ductor, and then uses the analog comparator (ACMP) to measure the oscillation decay time. The oscillation decay time will be affected
by the presence of metal objects within a few millimeters of the inductor.
The LC sensor can be used for implementing a sensor that wakes up the EFM32 from sleep when a metal object comes close to the
inductor, which again can be used as a utility meter pulse counter, door alarm switch, position indicator or other applications where one
wants to sense the presence of a metal object.
PB12 (VDAC0_OUT1)
PC3 (ACMP0X/0Y CH3)
DAC_LC_EXCITE
EFM32
LC Sensor
LES_LC_SENSE
100R
100nF
330pF
390uH
1.5K
Figure 6.6. LC Metal Sensor
For more information about usage and theory of operation of the LC sensor, please refer to application note AN0029 Low Energy Sen-
sor Interface - Inductive Sense
UG287: EFM32 Giant Gecko GG11 Starter Kit User's Guide
Peripherals
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