3.4.1 Si7021 Relative Humidity and Temperature Sensor
The Si7021 I
2
C relative humidity and temperature sensor is a monolithic CMOS IC integrating humidity and temperature sensor ele-
ments, an analog-to-digital converter, signal processing, calibration data, and an I
2
C interface. The patented use of industry-standard,
low-K polymeric dielectrics for sensing humidity enables the construction of low-power, monolithic CMOS Sensor ICs with low drift and
hysteresis, and excellent long term stability. The Si7021 offers an accurate, low-power, factory-calibrated digital solution ideal for meas-
uring humidity, dew-point, and temperature in applications ranging from HVAC/R and asset tracking to industrial and consumer plat-
forms.
On xG24 Dev Kit, the Si7021 is connected through a switch. The switch must therefore be enabled by setting PC09 high before it can
be used by the application. This enables power to the Si7021 and connects the I
2
C lines used for the sensor to the EFR32MG24 I
2
C
bus. The application code should always drive the PC09 signal either high or low to prevent it from floating. The figure below shows
how the Si7021 is connected to the EFR32MG24.
Si7021
Temperature
& Humidity
Sensor
VMCU
EFR32MG24
PC04
PC05
PC09
VDD_SENSOR
I2C_SCL
I2C_SDA
SENSOR_ENABLE
SENSOR_I2C_SCL
SENSOR_I2C_SDA
0: Sensor is not powered
1: Sensor is powered
Figure 3.4. Si7021 Relative Humidity and Temperature Sensor
Although measures have been taken to thermally isolate the sensor from the board, temperature readings will be influenced when pow-
er is dissipated on the board. More accurate temperature measurements are achieved when powering the board with a battery or
through the Mini Simplicity connector as self-heating from the on-board LDO is eliminated and the on-board debugger is put in a low
power state.
3.4.2 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 amplifi-
er, 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. Applications for the Si7210 include mechanical position sensing in consum-
er, industrial, and automotive applications, reed switch replacement, fluid level measurement, speed sensing, and control knobs, and
switches.
On xG24 Dev Kit, the Si7210 is connected through a switch. The switch must therefore be enabled by setting PC09 high before it can
be used by the application. This enables power to the Si7210 and connects the I
2
C lines used for the sensor to the EFR32MG24 I
2
C
bus. The application code should always drive the PC09 signal either high or low to prevent it from floating. The figure below shows
how the Si7210 is connected to the EFR32MG24.
VMCU
EFR32MG24
PC04
PC05
PC09
VDD_SENSOR
I2C_SCL
I2C_SDA
SENSOR_ENABLE
SENSOR_I2C_SCL
SENSOR_I2C_SDA
0: Sensor is not powered
1: Sensor is powered
Si7210
Hall Effect
Sensor
Figure 3.5. Hall Effect Sensor
UG524: xG24 Dev Kit User's Guide
Hardware
silabs.com
| Building a more connected world.
Rev. 0.1 | 12
