UG309: Thunderboard Sense 2 User's
Guide
The Thunderboard™ Sense 2 is the ultimate multi-sensor, multiprotocol cloud inspiration kit.
The board is a small and cost-effecitve, feature-rich prototype and development platform based on the EFR32™ Mighty Gecko Wireless System-on-Chip. The Thunderboard Sense 2 is an ideal platform for developing energy-friendly connected IoT devices. This is a true multiprotocol capable kit, supporting proprietary stacks and standard
protocols such as Zigbee, Thread and Bluetooth® low energy.
The Thunderboard Sense 2 ships with a ready-to-use Bluetooth demo that works with a
cloud connected smartphone app, showcasing easy collection of environmental and
motion sensor data.
A built in SEGGER J-Link debugger ensures easy customization and development.
KEY POINTS
• EFR32MG12 Mighty Gecko Wireless SoC
with 38.4 MHz operating frequency, 1024
kB flash and 256 kB RAM
• 2.4 GHz ceramic chip antenna
• Fine-grained power-control for ultra-lowpower operation
• Seven sensors and four high brightness
controllable RGB LEDs
• User LEDs/pushbuttons
• 8-Mbit flash for OTA programming and
data logging
• SEGGER J-Link on-board debugger
• Virtual COM port
• Packet Trace
• Mini Simplicity connector for connection
to an external Silicon Labs debugger
• 20-pin 2.54 mm breakout pads
• Power sources include USB, coin cell and
external batteries
ON-BOARD SENSORS
• Relative humidity and temperature sensor
• UV index and ambient light sensor
• Hall effect sensor
• Indoor air quality gas sensor
• 6-axis inertial sensor
• Barometric pressure sensor
• MEMS microphone
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SOFTWARE SUPPORT
• Simplicity Studio™
ORDERING INFORMATION
• SLTB004A
| Building a more connected world. Rev. 1.1
Table of Contents
1. Introduction ................................4
1.1 Kit Contents ...............................4
1.2 Hardware Content .............................5
1.3 Kit Hardware Layout ............................5
2. Specifications ...............................6
2.1 Absolute Maximum Ratings..........................6
2.2 Recommended Operating Conditions ......................6
2.3 Current Consumption ............................7
3. Hardware .................................9
3.1 Block Diagram ..............................9
3.2 Power Supply ..............................10
3.3 EFR32MG12 Reset ............................11
3.4 Sensors and RGB LEDs ...........................11
3.4.1 Si7021 Relative Humidity and Temperature Sensor ................12
3.4.2 Si1133 UV Index and Ambient Light Sensor...................12
3.4.3 BMP280 Barometric Pressure Sensor .....................13
3.4.4 Si7210 Hall Effect Sensor .........................13
3.4.5 CCS811 Indoor Air Quality Gas Sensor ....................14
3.4.6 ICM-20648 6-Axis Inertial Sensor ......................15
3.4.7 ICS-43434 MEMS Microphone .......................16
3.4.8 RGB LEDs ..............................17
3.5 Push Buttons and RG LED ..........................18
3.6 Memory ................................18
3.7 On-board Debugger ............................19
3.8 Connectors ...............................20
3.8.1 Breakout Pads ............................21
3.8.2 Mini Simplicity Connector .........................22
3.8.3 USB Micro-B Connector .........................22
3.8.4 Battery Connector ...........................22
4. Debugging ...............................23
4.1 On-board Debugger Considerations .......................23
4.2 Virtual COM Port .............................24
4.3 Mini Simplicity Connector ..........................24
5. Radio .................................25
5.1 RF Section ...............................25
5.1.1 Description of the RF Matching .......................25
5.1.2 RF Section Power Supply .........................25
5.1.3 RF Matching Bill of Materials ........................25
5.1.4 Antenna ...............................26
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5.1.5 Antenna Matching Bill of Materials ......................26
5.2 EMC Regulations for 2.4 GHz .........................27
5.2.1 ETSI EN 300-328 Emission Limits for the 2400-2483.5 MHz Band ...........27
5.2.2 FCC15.247 Emission Limits for the 2400-2483.5 MHz Band .............27
5.2.3 Applied Emission Limits .........................27
5.3 Radiated Power Measurements ........................28
5.3.1 Maximum Radiated Power Measurement ...................28
5.3.2 Antenna Pattern Measurement .......................29
5.4 EMC Compliance Recommendations ......................31
5.4.1 Recommendations for 2.4 GHz ETSI EN 300-328 Compliance ............31
5.4.2 Recommendations for 2.4 GHz FCC 15.247 Compliance ..............31
6. Schematics, Assembly Drawings and BOM ...................32
7. Kit Revision History and Errata .......................33
7.1 Revision History .............................33
8. Board Revision History and Errata ......................34
8.1 Revision History .............................34
8.2 Errata .................................34
9. Document Revision History .........................35
silabs.com
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UG309: Thunderboard Sense 2 User's Guide
Introduction
1. Introduction
The Thunderboard Sense 2 has been designed to inspire customers to make battery operated IoT devices with the Silicon Labs
EFR32MG12 Mighty Gecko Wireless System-on-Chip. The highlights of the board include seven different environmental sensors and
four high brightness RGB LEDs accessible to the EFR32MG12 wireless MCU. The sensors and LEDs have been grouped into power
domains that can be turned on and off by the application code as needed. By default, the board starts up in the lowest power operating
mode, with all sensors disabled.
Programming the Thunderboard Sense 2 is easily done using a USB Micro-B cable and the on-board J-Link debugger. A USB virtual
COM port provides a serial connection to the target application. Included on the board is an 8 Mbit serial flash that can be used for
Over-The-Air (OTA) firmware upgrade, or as a general purpose non-volatile memory. The Thunderboard Sense 2 is supported in Simplicity Studio™, and a Board Support Package (BSP) is provided to give application developers a flying start.
Energy profiling and advanced wireless network analysis and debugging tools are available through the provided Mini Simplicity Connector using an external Silicon Labs debugger. See AN958: Debugging and Programming Interfaces for Custom Designs for more information about debugging and programming interfaces that can be used with Silicon Labs' starter kits.
Connecting external hardware to the Thunderboard Sense 2 can be done using the 20 breakout pads which present peripherals from
the EFR32MG12 Mighty Gecko such as I2C, SPI, UART and GPIOs. The breakout pads follow the same pinout as the expansion head-
ers (EXP) on other Silicon Labs Starter Kits.
Figure 1.1. Thunderboard Sense 2
1.1 Kit Contents
The following items are included in the box:
• 1x Thunderboard Sense 2 board (BRD4166A)
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Top View
Bottom View
RGB LED 0
RGB LED 2
Push Button 0
Push Button 1
30 mm
45 mm
Reset Button
Acoustic hole
RGB LED 1
BMP280 Pressure
Sensor
CCS811 Indoor
Air Quality Sensor
20-pin EXP-header
Breakout Pads
ICM-20648 6-axis
Inertial Sensor
USB Micro-B Connector
- Virtual COM port
- Debug access
Si7210 Hall Effect
Sensor
Si7021 Humidity and
Temperature Sensor
Mini-Simplicity
Connector
Si1133 Ambient
Light & UV
Sensor
EFR32MG12
Mighty Gecko
2.4 GHz
Chip Antenna
ICS-43434 MEMS
Microphone
On-board USB
J-Link Debugger
External Battery
Connector
CR2032 Coin Cell
Holder
RGB LED 3
UG309: Thunderboard Sense 2 User's Guide
1.2 Hardware Content
The following key hardware elements are included on the Thunderboard Sense 2:
• EFR32MG12 Mighty Gecko Wireless SoC with 38.4 MHz operating frequency, 1024 kB flash and 256 kB RAM
• 2.4 GHz ceramic antenna for wireless transmission
• Silicon Labs Si7021 relative humidity and temperature sensor
• Silicon Labs Si1133 UV index and ambient light sensor
• Silicon Labs Si7210 hall effect sensor
• Bosch Sensortec BMP280 barometric pressure sensor
• ams CCS811 indoor air quality gas sensor
• TDK InvenSense ICM-20648 6-axis inertial sensor
• TDK InvenSense ICS-43434 MEMS microphone
• Four high brightness RGB LEDs from Broadcom Limited (ASMT-YTB7-0AA02)
• One bi-color LED and two push buttons
• Power enable signals for fine grained power-control
• Macronix ultra-low-power 8-Mbit SPI flash (MX25R8035F)
• On-board SEGGER J-Link debugger for easy programming and debugging, which includes a USB virtual COM port
• Mini Simplicity connector for access to energy profiling and advanced wireless network debugging
• Breakout pads for GPIO access and connection to external hardware
• Reset button
• Automatic switchover between USB and battery power
• CR2032 coin cell holder and external battery connector
Introduction
1.3 Kit Hardware Layout
The layout of the Thunderboard Sense 2 is shown below.
Figure 1.2. Thunderboard Sense 2 Hardware Layout
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UG309: Thunderboard Sense 2 User's Guide
Specifications
2. Specifications
2.1 Absolute Maximum Ratings
Parameter Symbol Min Typ Max Unit
USB Input Voltage V
Battery Input Voltage (VMCU) V
LDO output current I
USB-MAX
BAT-MAX
VREG-LOAD
Voltage on any I/O breakout pad V
Current per I/O pin (sink) I
Current per I/O pin (source) I
Current for all I/O pins (sink) I
Current for all I/O pins (source) I
IOALLMAX
IOALLMAX
ESD Susceptibility HBM (Human Body Model) V
DIGPIN
IOMAX
IOMAX
ESD
0 +5.5 V
0 +3.6 V
300 mA
-0.3 VMCU+0.3 V
50 mA
50 mA
200 mA
200 mA
2 kV
2.2 Recommended Operating Conditions
Parameter Symbol Min Typ Max Unit
USB Supply Input Voltage V
Battery Supply Input Voltage V
Supply Input Voltage (VMCU supplied externally) V
Operating Temperature
1
USB
VBAT
VMCU
T
OP
+4.5 +5.0 +5.5 V
+2.0 +3.3 V
+2.0 +3.3 V
-35 85 ˚C
1 Using the CCS811 gas sensor limits the operating temperature range from -5 to 50 ˚C.
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UG309: Thunderboard Sense 2 User's Guide
Specifications
2.3 Current Consumption
The operating current of the board greatly depends on the application. The number of enabled sensors, how often they are sampled,
and how often the radio is transmitting or receiving are examples of factors that influence the operating current. The table below attempts to give some indication of how different features of the board contribute to the overall power consumption. Note that some numbers are measured values, while others are taken from the data sheets for the devices. For a full overview of the conditions that apply
for a specific number from a data sheet, the reader is encouraged to read the specific data sheet.
Table 2.1. Current Consumption
Parameter Symbol Condition Min Typ Max Unit
EFR32 Current Consumption
UV/ALS Current Consumption
1
2
I
EFR32
I
Si1133
EFR32 in EM0 Active mode. 3.4 mA
Radio in receive mode. 10 mA
Radio transmitter active @ 8 dBm 26 mA
Standby 0.125 µA
ADC Conversion in Progress 0.525 µA
RH/Temp Sensor Current Consumption
Barometric Pressure Sensor Current Consumption
Microphone Current Consumption
CCS811 Current Consumption
IMU Current Consumption
4
5
6
7
Responding to commands and calculat-
4.5 mA
ing results
3
I
Si7021
Standby, -40 to +85˚C 0.06 0.62 µA
RH conversion in progress 150 180 µA
Temperature conversion in progress 90 120 µA
3.5 4.0 mA
2.8 4.2 µA
I
BMP280
Peak IDD during I2C operations
Sleep current 0.1 0.3 µA
1 Hz forced mode, pressure & temperature, lowest power
Peak current during pressure measure-
0.72 1.12 mA
ment
Current at temperature measurement 0.33 mA
I
Sleep mode current (fs<3.125 kHz) 12 20 uA
MIC
Supply current in high-performance mode
490 550 uA
with VDD = 1.8 V and no load
I
CCS811
Enabled, sleep mode at 1.8 V supply 19 µA
During measurement at 1.8 V supply 26 mA
Average over pulse cycle at 1.8 V supply 0.7 mA
I
Full-chip sleep mode at 1.8 V supply 8 µA
IMU
Gyroscope only, 102.3 Hz update rate at
1.23 mA
1.8 V supply
Accelerometer only, 102.3 Hz update
68.9 µA
rate at 1.8 V supply
Gyroscope + Accelerometer, 102.3 Hz
1.27 mA
update rate at 1.8 V supply
RGB LED Current Consumption
8
I
RGB
Power enabled, all LEDs off 65 µA
Additional current for each enabled LED 10 µA
Current per LED, all colors 100% duty cy-
29.9 mA
cle
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UG309: Thunderboard Sense 2 User's Guide
Specifications
Parameter Symbol Condition Min Typ Max Unit
On-board Debugger Current Consumption8I
DBG
1 From EFR32MG12 Mighty Gecko SoC data sheet
2 From Si1133 data sheet
3 From Si7021-A20 data sheet
4 From BMP280 data sheet
5 From ICS-43434 data sheet
6 From CCS811 data sheet
7 From ICM-20648 data sheet
8 Measured values
USB cable inserted, current sourced from
USB 5V
USB cable removed, current sourced
from VMCU rail.
29 mA
20 nA
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Memory
Si7021
CCS811
Si7210
Si1133
ICS-43434
ICM-20648
Sensors
Radio
Device Connectivity & Debugging
x4
BMP280
J-Link
Debugger
USB Micro-B
Connector
2.4 GHz
Antenna
8 Mbit
MX25R
Buttons and LEDs
EFR32MG12
Wireless SoC
Breakout Pads
(EXP-Header pinout)
RGB LEDs
Temperature
& Humidity
Sensor
Ambient
Light & UV
Sensor
Hall Effect
Sensor
MEMS
Microphone
6-axis Inertial
Sensor
Pressure
Sensor
Indoor
Air Quality
Sensor
RGB LEDs
User Buttons
& RG LED
Mini-Simplicity
Connector
Serial Flash
UG309: Thunderboard Sense 2 User's Guide
Hardware
3. Hardware
The core of the Thunderboard Sense 2 is the EFR32MG12 Mighty Gecko Wireless System-on-Chip. The board also contains a multitude of sensors, including various environmental sensors and a motion sensor, all connected to the EFR32MG12. The user interface
components include push buttons, a bi-colour LED, and four high brightness RGB LEDs.
The key aspects of the hardware will be explained in this chapter, while in-depth information on the EFR32MG12 Mighty Gecko SoC
can be found in the EFR32MG12 data sheet and reference manual. For placement and layout of the hardware components the reader
is referred to section 1.3 Kit Hardware Layout.
3.1 Block Diagram
An overview of the Thunderboard Sense 2 is illustrated in the figure below.
Figure 3.1. Kit Block Diagram
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USB micro-B
LDO
5V0
IN
OUT
Automatic
Switchover
3V3
VMCU
Battery
EFR32MG12
Wireless SoC
Peripherals
Peripherals
Peripherals
Peripherals
Mini Simplicity
Connector
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.2 Power Supply
There are several ways to power the kit. The options include battery, on-board LDO from USB and the Mini Simplicity connector. Figure
3.2 Thunderboard Sense 2 Power Options on page 10 shows the power options available on the kit and illustrates the main system
power architecture.
Figure 3.2. Thunderboard Sense 2 Power Options
In normal operation, power can be applied using either a USB cable connected to a power source, or a battery connected to one of the
battery connectors. The 5 V power net on the USB bus is regulated down to 3.3 V using a low-dropout regulator. An automatic switchover circuit switches the main system power from battery power to USB power when the USB cable is inserted, and prevents charging
of the battery.
Batteries can be connected to the Thunderboard Sense 2 using either the CR2032 coin cell holder or the external battery connector. A
CR2032 coin cell is sufficient for low-power operation that does not require high peak current. More demanding applications, such as
enabling the RGB LEDs at high intensities, might need a higher capacity external battery or USB power. Do not connect batteries to
both the CR2032 coin cell connector and the external battery connector simultaneously, as there are no protection mechanisms between the two battery connectors.
Important: Do not connect batteries to both the CR2032 coin cell holder and the external battery connector simultaneously.
A third option for powering the Thunderboard Sense 2 exists through the Mini Simplicity connector. Powering the Thunderboard Sense
2 through the Mini Simplicity connector with an external Silicon Labs debugger allows accurate current measurements using the Advanced Energy Monitoring (AEM) feature of the external debugger. This option requires that no other power sources are present on the
kit, as the power is injected directly to the VMCU net. Doing so will cause conflict between the two regulators and erroneous AEM
measurements. For more information about using the Mini Simplicity connector, refer to section 4.3 Mini Simplicity Connector.
Important: When powering the board through the Mini Simplicity connector, the USB and battery power sources must be removed.
The power supply options are summarized in the table below. For placement of the USB and battery connectors, the reader is referred
to section 1.3 Kit Hardware Layout.
Table 3.1. Thunderboard Sense 2 Power Options
Supply Mode VIN VMCU 3V3 5V0
USB power 4.5 - 5.5 V On-board regulator On-board regulator USB VBUS
CR2032 battery 2.0 - 3.3 V Battery voltage Turned off and isolated No voltage present
External battery 2.0 - 3.3 V Battery voltage Turned off and isolated No voltage present
Mini Simplicity 2.0 - 3.3 V Debugger dependent Turned off and isolated No voltage present
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PC10 (I2C0_SCL#14)
PC11 (I2C0_SDA#16)
EFR32MG
EFR32MG12
CCS811
ICM-20648
BMP280
Si7021
Si1133
Si7210
RGB LEDs
x4
ICS-43434
VMCU
IOVDD
ENV_SENSE_ENABLE
ENV_I2C
VMCU
UV_ALS_INT
VMCUVMCU VMCU
IMU_ENABLE
CCS811_ENABLE
HALL_ENABLE
IMU_SPI
IMU_INT
CCS811_I2C
CCS811_#WAKE
CCS811_INT
HALL_I2C
HALL_OUT1
Power
Power
Power
Power
MIC_ENABLE
Power
MIC_I2S
DC/DC
EN
VMCU
Power[3:0]
RGB_LED_ENABLE
LED_COM[3:0]
LED_RGB[R,G,B]
3.5 V
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.3 EFR32MG12 Reset
The EFR32MG12 Wireless SoC can be reset by a few different sources:
• A user pressing the RESET button.
• The on-board debugger pulling the #RESET pin low.
• An external debugger pulling the #RESET pin low.
3.4 Sensors and RGB LEDs
The Thunderboard Sense 2 contains seven different sensors and four high brightness RGB LEDs which can be accessed from the
EFR32MG12.
• Silicon Labs Si7021 relative humidity & temperature sensor
• Silicon Labs Si1133 UV index & ambient light sensor
• Silicon Labs Si7210 hall effect sensor
• Bosch Sensortec BMP280 barometric pressure sensor
• ams CCS811 indoor air quality gas sensor
• TDK InvenSense ICM-20648 6-axis inertial measurement sensor
• TDK InvenSense ICS-43434 MEMS microphone
• Four high brightness RGB LEDs from Broadcom Limited (ASMT-YTB7-0AA02)
All the sensors have enable signals which can be used to completely turn off sensors that are not in use. This allows for the lowest
possible power consumption in every application. Three of the environmental sensors have been grouped together and share the same
power supply enable signal, while the remaining sensors have individual enable signals. The dc-dc converter that powers the high
brightness RGB LEDs can be turned off when the LEDs are not in use, and each RGB LED have furthermore its own power supply
enable signal.
An overview of the connection and power topology of the sensors and RGB LEDs are given in the figure below.
Figure 3.3. Sensors and RGB LEDs
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0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
ENV_I2C_SCL
ENV_I2C_SDA
Si7021
Temperature
& Humidity
Sensor
VDD
ENV_SENSE_ENABLE
VDD_ENV_SENSE
VMCU
SCL
SDA
PF9 (GPIO)
PC4 (I2C1_SDA#17)
PC5 (I2C1_SCL#17)
IOVDD
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
ENV_I2C_SCL
ENV_I2C_SDA
VDD
ENV_SENSE_ENABLE
VDD_ENV_SENSE
VMCU
SCL
SDA
Si1133
Ambient
Light & UV
Sensor
UV_ALS_INT
PF9 (GPIO)
PC4 (I2C1_SDA#17)
PC5 (I2C1_SCL#17)
PF11 (GPIO)
IOVDD
INT
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.1 Si7021 Relative Humidity and Temperature Sensor
The Si7021 I2C relative humidity and temperature sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-to-digital converter, signal processing, calibration data, and an I2C 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 measuring humidity, dew-point, and temperature,
in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.
On Thunderboard Sense 2, the Si7021 is powered down by default through a power isolation switch. The power switch must therefore
be enabled by setting PF9 high before it can be accessed through the I2C interface. Note that both the Si7021, Si1133, and the
BMP280 all share the same power isolation switch and I2C interface, and hence, all the sensors are powered up once PF9 is set high.
The hardware connection is illustrated in Figure 3.4 Si7021 Relative Humidity and Temperature Sensor on page 12.
Figure 3.4. Si7021 Relative Humidity and Temperature Sensor
Note: Due to self-heating from the on-board LDO, temperature measurements are slightly off when running off USB power. More accu-
rate temperature measurements are achieved when powering the board with a battery or through the Mini Simplicity connector.
3.4.2 Si1133 UV Index and Ambient Light Sensor
The Si1133 is a UV index and ambient light sensor with I2C digital interface and programmable event interrupt output. This sensor IC
includes dual 23-bit analog-to-digital converters, integrated high-sensitivity array of UV, visible and infrared photodiodes, and digital signal processor.
On Thunderboard Sense 2, the Si1133 is powered down by default through a power isolation switch. The power switch must therefore
be enabled by setting PF9 high before it can be accessed through the I2C interface. Note that both the Si1133, Si7021 and the BMP280
all share the same power isolation switch and I2C interface, and hence, all the sensors are powered up once PF9 is set high. The hard-
ware connection is illustrated in Figure 3.5 Si1133 UV and Ambient Light Sensor on page 12.
Figure 3.5. Si1133 UV and Ambient Light Sensor
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BMP280
Pressure
Sensor
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
ENV_I2C_SCL
ENV_I2C_SDA
VDD
ENV_SENSE_ENABLE
VDD_ENV_SENSE
VMCU
SCL
SDA
PF9 (GPIO)
PC4 (I2C1_SDA#17)
PC5 (I2C1_SCL#17)
IOVDD
Si7210
Hall Effect
Sensor
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
HALL_I2C_SCL
HALL_I2C_SDA
VDD
HALL_ENABLE
VDD_HALL
VMCU
SCL
SDA
HALL_OUT1
PB10 (GPIO)
PB8 (I2C1_SDA#8)
PB9 (I2C1_SCL#8)
PB11 (PCNT0_S0IN#6)
IOVDD
VOUT
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.3 BMP280 Barometric Pressure Sensor
The BMP280 is a combined absolute barometric pressure sensor and temperature sensor with a digital interface supporting both SPI
and I2C. No external sensing elements are needed, and the device has an integrated ADC and ASIC with built-in configurable IIR filter
to suppress noise. Selectable oversampling rates provide trade-off between low power and high resolution, and an option to skip either
temperature or pressure measurement is available in case one or the other is unnecessary.
On Thunderboard Sense 2, the BMP280 is powered down by default through a power isolation switch. The power switch must therefore
be enabled by setting PF9 high before it can be accessed through the I2C interface. Note that both the BMP280, Si1133, and Si7021 all
share the same power isolation switch and I2C interface, and hence, all the sensors are powered up once PF9 is set high. The hard-
ware connection is illustrated in Figure 3.6 BMP280 Absolute Pressure Sensor on page 13.
Figure 3.6. BMP280 Absolute Pressure Sensor
3.4.4 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 I2C 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 I2C 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 replacement, fluid level measurement, speed sensing, and control knobs and switches. Refer to the Si7210 data sheet for more information.
On Thunderboard Sense 2, the Si7210 is powered down by default through a power isolation switch. The power switch must therefore
be enabled by setting PB10 high before it can be accessed through the I2C interface. The hardware connection is illustrated in Figure
3.7 Hall Effect Sensor on page 13.
Figure 3.7. Hall Effect Sensor
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CCS811
Indoor
Air Quality
Sensor
SDA
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
CCS811_I2C_SCL
CCS811_I2C_SDA
VDD
CCS811_ENABLE
VDD_CCS811
VMCU
SCL
CCS811_INT
CCS811_#WAKE
PF14 (GPIO)
PB6 (I2C1_SDA#6)
PB7 (I2C1_SCL#6)
PF13 (GPIO)
PF15 (GPIO)
IOVDD
nINT
nWAKE
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.5 CCS811 Indoor Air Quality Gas Sensor
The CCS811 is a digital gas sensor solution for indoor air quality monitoring (IAQ). The sensor detects a wide range of volatile organic
compounds (VOCs) and it calculates and provides the equivalent CO2 concentration and the total volatile organic compound concentra-
tion. The device uses the I2C interface for data transfer.
On Thunderboard Sense 2, the CCS811 is powered down by default through a power isolation switch. To use the sensor, power must
be enabled to the sensor, and it has to be woken up from sleep using the sensor's dedicated "wake" pin. Power is enabled by setting
PF14 high and the sensor is woken up by pulling PF15 low. The CCS811 has furthermore an interrupt pin that can generate an interrupt
signal whenever a new sample is ready. The hardware connection is illustrated in Figure 3.8 CCS811 Indoor Air Quality and Gas Sen-
sor on page 14.
Figure 3.8. CCS811 Indoor Air Quality and Gas Sensor
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X
Pin 1 chip
identifier
Z
Y
ICM-20648
6-axis Intertial
Sensor
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
VMCU
IMU_SPI_MISO
IMU_SPI_MOSI
VDD
IMU_ENABLE
VDD_IMU
VMCU
nCS
INT
IMU_SPI_SCLK
IMU_SPI_CS
IMU_INT
SCLK
MOSI
MISO
PF8 (GPIO)
PF12 (GPIO)
PC3 (US3_CS#18)
PC2 (US3_CLK#18)
PC0 (US3_TX#18)
PC1 (US3_RX#18)
IOVDD
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.6 ICM-20648 6-Axis Inertial Sensor
The ICM-20648 is a 6-axis inertial sensor consisting of a 3-axis gyroscope and a 3-axis accelerometer. The sensor detects acceleration
and angular rate in and around the X-, Y-, and Z-axes with integrated 16-bit ADCs and programmable digital filters. The device supports
both the SPI and I2C interface.
On Thunderboard Sense 2, the inertial sensor is located in the center of the board. The coordinate system and rotation of the sensor
follows the right-hand rule, and the spatial orientation of the board is shown in Figure 3.9 Thunderboard Sense 2 Spatial Orientation on
page 15.
Figure 3.9. Thunderboard Sense 2 Spatial Orientation
On Thunderboard Sense 2, the ICM-20648 is powered down by default through a power isolation switch. The power switch must therefore be enabled by setting PF8 high before it can be accessed through the SPI interface. The ICM-20648 has furthermore an interrupt
pin which, when enabled, generates an interrupt signal whenever a new sample is ready. The hardware connection is illustrated in
Figure 3.10 ICM-20648 Nine-axis Inertial Sensor on page 15.
Figure 3.10. ICM-20648 Nine-axis Inertial Sensor
silabs.com | Building a more connected world. Rev. 1.1 | 15
ICS-43434
MEMS
Microphone
0: Sensor is not powered
1: Sensor is powered
EFR32MG12
MIC_I2S_SCK
MIC_I2S_SD
VDD
MIC_ENABLE
VMCU
SCK
SD
MIC_I2S_WS
WS
PF10 (GPIO)
PC7 (US1_RX#11)
PC8 (US1_CLK#11)
PC9 (US1_CS#11)
IOVDD
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.7 ICS-43434 MEMS Microphone
The ICS-43434 is an omnidirectional MEMS microphone with a wideband frequency response and a digital I2S output. The sensor is a
complete solution and includes, amongst others, a MEMS sensor, signal conditioning, ADC, filters, and different operating modes. The
ICS-43434 is a bottom port microphone, and it is placed on the bottom side of Thunderboard Sense 2 with an acoustic ventilation hole
going through to the top side. This hole lets sound waves into the microphone package.
On Thunderboard Sense 2, the ICS-43434 is powered using the GPIO pin on the EFR32MG12. The sensor is powered by setting PF10
high, and powered down by pulling the pin low. The hardware connection is illustrated in Figure 3.11 ICS-43434 MEMS Microphone on
page 16.
Figure 3.11. ICS-43434 MEMS Microphone
silabs.com | Building a more connected world. Rev. 1.1 | 16
EFR32MG12
LED_RGB_RED
LED_RGB_BLUE
LED_RGB_GREEN
DC/DC
3.5 V
EN
RGB_LED_ENABLE
LED_COM[3:0]
RGB LEDRGB LED 0 RGB LED 1 RGB LED 2 RGB LED 3
DC/DC
EN
VMCU
VMCU
0: RGB LED is not powered
1: RGB LED is powered
0: Regulator is not enabled
1: Regulator is enabled
4
PJ14 (GPIO)
PI[3:0] (GPIOs)
PD11 (TIM0_CC0#19)
PD12 (TIM0_CC1#19)
PD13 (TIM0_CC2#19)
IOVDD
0: Cathode is pulled to ground, and the
LEDs for the corresponding color are enabled
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.4.8 RGB LEDs
The RGB LEDs are driven from a 3.5 V rail that is generated by a boost regulator. This ensures that the color representation remains
constant even if the battery voltage drops below the LED forward voltage (Vf).
The boost regulator is enabled by setting PJ14 high, and each LED can be individually enabled by setting PI0, PI1, PI2, or PI3 high.
The cathodes of the same color of each LED are tied together, so that all enabled RGB LEDs will show the same color. The RGB LED
hardware includes fast low-side drivers, so that any color can be created using the TIMER peripheral in the EFR32 in pulse width modulation (PWM) mode. The hardware connection is illustrated in Figure 3.12 LEDs on page 17.
Figure 3.12. LEDs
Because of the high current consumption, the RGB LEDs are not suitable for use in a coin cell application. Even with a low duty cycle
PWM, the pulsed current can easily exceed 100 mA when all LEDs are enabled. Because of the boost regulator, the actual current
drain increases slightly as the battery voltage decreases.
Table 3.2. RGB LED Typical Power Consumption at 3.3 V VMCU
Color 1x LED 2x LEDs 3x LEDs 4x LEDs
Red, 100% duty cycle 13.4 mA 26.8 mA 40.2 mA 53.6 mA
Green, 100% duty cycle 8.0 mA 16.0 mA 24.0 mA 32.0 mA
Blue, 100% duty cycle 8.5 mA 17.0 mA 25.5 mA 34.0 mA
All, 100% duty cycle (white) 29.9 mA 59.8 mA 89.7 mA 119.6 mA
Turning off the boost regulator and the individual RGB LEDs reduces the quiescent current to about 100 nA typically. Turning on the
boost regulator increases the quiescent current to about 65 µA, even with no LEDs enabled. Due to the high side drivers, each enabled
LED adds an additional 10 µA of quiescent current even if the red, green and blue signals are all off.
silabs.com | Building a more connected world. Rev. 1.1 | 17
EFR32MG12
PUSH_BUTTON0
LED_GREEN
PUSH_BUTTON1
User Buttons
& RG LED
LED_RED
PD8 (GPIO)
PD9 (GPIO)
PD14 (GPIO_EM4WU4)
PD15 (GPIO)
EFR32MG12
FLASH_SCLK
FLASH_MOSI
FLASH_MISO
FLASH_CS
Serial Flash
8 Mbit
MX25R
VMCU
PF7 (US2_CLK#18)
PK0 (US2_TX#29)
PK2 (US2_RX#30)
PK1 (US2_CS#27)
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.5 Push Buttons and RG LED
The kit has two user push buttons. Push button 0 is located at the bottom left corner of the board, while push button 1 is located at the
bottom right corner of the board. The push buttons are connected to pin PD14 and PD15 respectively. Both push buttons are active low
and de-bounced by an RC filter with a time constant of 1 ms.
The board contains a small bi-color LED that is connected to PD8 and PD9 through current limiting resistors. The current consumption
of this LED is fairly low compared to the RGB LEDs, so the use of this LED is suitable for coin cell applications. The red LED consumes
about 0.8 mA @ 3.3 V, and the green LED about 0.7 mA @ 3.3 V.
The hardware connection is illustrated in Figure 3.13 Push Buttons on page 18.
Figure 3.13. Push Buttons
3.6 Memory
The Thunderboard Sense 2 is equipped with an 8-Mbit Macronix SPI Flash that is connected directly to the EFR32MG12 Mighty Gecko.
Figure 3.14 Serial Flash on page 18 shows how the serial flash is connected to the EFR32MG12.
Figure 3.14. Serial Flash
The MX25R series are ultra-low-power serial flash devices, so there is no need for a separate enable switch to keep current consumption down. However, it is important that the flash is always put in deep power down mode when not used. This is done by issuing a
command over the SPI interface. In deep power down, the MX25R typically adds approximately 100 nA to the current consumption.
silabs.com | Building a more connected world. Rev. 1.1 | 18
Mini Simplicity
Connector
EFR32MG
PC11 (I2C0_SCL#15)
EFR32MG12
PF0 (DBG_SCLK)
PF1 (DBG_SWDIO)
PF2 (DBG_SWO#0)
PA0 (US0_TX#0)
PA1 (US0_RX#0)
PA3 (US0_RTS#30)
PA2 (US0_CTS#30)
VCOM_TX
VCOM_RX
VCOM_CTS
VCOM_RTS
DBG_SWCLK
DBG_SWDIO
DBG_SWO
On-Board
J-Link
Debugger
Host
PC
USB
DBG_RESET
RESETn
PTI_DATA
PTI_FRAME
PB12 (FRC_DOUT#6)
PB13 (FRC_DFRAME#6)
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.7 On-board Debugger
The Thunderboard Sense 2 contains a microcontroller separate from the EFR32MG12 Mighty Gecko that provides the user with a onboard J-Link debugger through the USB micro-B port. This microcontroller is referred to as the "On-board Debugger", and is not programmable by the user. When the USB cable is removed, the on-board debugger goes into a very low power shutoff mode (EM4S),
consuming around 20 nA typically.
The on-board debugger also provides additional features:
• The Packet Trace Interface (PTI), which is used in conjunction with PC software to provide detailed insight into an active radio network
• The Virtual COM Port, which provides a way to transfer application data between the host PC and the target processor
Figure 3.15 On-Board Debugger Connections on page 19 shows the connections between the target EFR32MG12 device and the on-
board debugger. The figure also shows the presence of the Mini Simplicity Connector, and how this is connected to the same I/O pins.
Refer to chapter 4. Debugging for more details on debugging.
Figure 3.15. On-Board Debugger Connections
silabs.com | Building a more connected world. Rev. 1.1 | 19
EXP2 - VMCU
EXP4 - SPI_MOSI - PK0
EXP18 - 5V
EXP20 - 3V3
EXP6 - SPI_MISO - PK2
EXP8 - SPI_SCLK - PF7
EXP10 - SPI_CS - PA5
EXP12 - UART_TX - PF3
EXP14 - UART_RX - PF4
EXP16 - I2C_SDA - PC10
GND - EXP1
PA8 - EXP3
PA9 - EXP5
PA6 - EXP7
PA7 - EXP9
PF5 - EXP11
PF6 - EXP13
PC11 - I2C_SCL - EXP15
BOARD_ID_SCL - EXP17
BOARD_ID_SDA - EXP19
1
3
5
7
9
11
13
15
17
19
2
4
6
8
10
12
14
16
18
20
Expansion Header
Breakout Pads
VMCU
RST
PA0 - VCOM_TX
PF1 - SWDIO
PB13 - PTI_FRAME
GND
VCOM_RX - PA1
SWO - PF2
SWCLK - PF0
PTI_DATA - PB12
Mini Simplicity
Connector
GND
VBAT
Hirose DF13C-2P-1.25V
Battery Connector
(on reverse side)
USB Micro-B
Connector
Mini-Simplicity
Connector
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.8 Connectors
The Thunderboard Sense 2 features a Mini Simplicity connector, a USB Micro-B connector and 20 breakout pads that follow the expansion header pinout. The connectors are placed on the top side of the board, and their placement and pinout can be seen in the following
figure. For additional information on the connectors, see the following sub chapters.
Figure 3.16. Thunderboard Sense 2 Connectors
silabs.com | Building a more connected world. Rev. 1.1 | 20
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.8.1 Breakout Pads
Twenty breakout pads, which follow the expansion header pinout, are provided and allow connection of peripherals or add-on boards.
Ten of the pads are located along the left side of the board while the remaining ten are located on the right side. The breakout pads
contain a number of I/O pins that can be used with most of the EFR32MG12 Mighty Gecko's features. Additionally, the VMCU (main
board power rail), 3.3 V (LDO regulator output) and 5 V power rails are also exported.
The breakout pads are pinned out similar to the expansion header found on other Silicon Labs starter kits, which ensures that commonly used peripherals such as SPI, UART, and I2C buses are available on fixed locations. The rest of the pins are used for general pur-
pose IO. This allows the definition of expansion boards that can plug into a number of different Silicon Labs starter kits.
The pin-routing on the EFR32 is very flexible, so most peripherals can be routed to any pin. However, some pins are shared between
the breakout pads and other functions on the Thunderboard Sense 2. Table 3.3 Expansion Header Pinout on page 21 includes an
overview of the expansion header and functionality that is shared with the kit.
Table 3.3. Expansion Header Pinout
Pin Connection EXP Header Function Shared Feature Peripheral Mapping
Right Side Breakout Pins
2 VMCU EFR32MG12 voltage domain, included in AEM measurements.
4 PK0 SPI_MOSI SPI Flash US2_TX #29
6 PK2 SPI_MISO SPI Flash US2_RX #30
8 PF7 SPI_SCLK SPI Flash US2_CLK #18
10 PA5 SPI_CS US2_CS #29
12 PF3 UART_TX LEU0_TX #27
14 PF4 UART_RX LEU0_RX #27
16 PC10 I2C_SDA I2C0_SDA #15
18 5V Board USB voltage
20 3V3 Board controller supply
Left Side Breakout Pins
1 GND Ground
3 PA8 GPIO
5 PA9 GPIO
7 PA6 GPIO
9 PA7 GPIO
11 PF5 GPIO
13 PF6 GPIO
15 PC11 I2C_SCL I2C0_SCL #15
17 BOARD_ID_SCL Connected to Board Controller for identification of add-on boards.
19 BOARD_ID_SDA Connected to Board Controller for identification of add-on boards.
silabs.com | Building a more connected world. Rev. 1.1 | 21
UG309: Thunderboard Sense 2 User's Guide
Hardware
3.8.2 Mini Simplicity Connector
The Mini Simplicity connector featured on the Thunderboard Sense 2 allows the use of an external debugger such as a Silicon Labs
Wireless Starter Kit (WSTK) with the board. In addition to providing serial wire debug (SWD) and virtual COM port functionality, the
WSTK can also support advanced energy profiling and wireless network analysis and debugging tools. The pinout, which is described
in the following table, is referenced from the EFR32MG12.
Table 3.4. Mini Simplicity Connector Pin Descriptions
Pin number Connection Function Description
1 VMCU VAEM Target voltage on the debugged application. Supplied and monitored
by the AEM when powered by a WSTK with its power selection switch
in the "AEM" position.
2 GND GND Ground.
3 EFR32MG12 reset pin DBG_RST Reset.
4 PA1 VCOM_RX Virtual COM Rx.
5 PA0 VCOM_TX Virtual COM Tx.
6 PF2 DBG_SWO Serial Wire Output.
7 PF1 DBG_SWDIO Serial Wire Data.
8 PF0 DBG_SWCLK Serial Wire Clock.
9 PB13 PTI_FRAME Packet Trace Frame Signal.
10 PB12 PTI_DATA Packet Trace Data Signal.
3.8.3 USB Micro-B Connector
The USB port can be used for uploading code, debugging, and as Virtual COM port, as described in section 4. Debugging.
3.8.4 Battery Connector
A small battery connector can be found on the secondary side of the board, above the CR2032 coin cell holder. This is a 1.25 mm pitch
miniature crimping connector from Hirose (P/N: DF13C-2P-1.25V).
The positive supply input pin on this connector (VBAT) is directly connected to the coin cell holder +terminal, so only one battery should
be used at a time to prevent current flow between batteries. The Thunderboard Sense 2 contains a small transistor switch circuit that
protects the board from reverse polarity on VBAT. When the USB cable is inserted, the transistor is turned off to prevent the on-board
LDO from charging the battery connected either to the battery connector or to the coin cell holder.
P/N for mating products:
• Single row socket, 2 pos: Hirose DF13-2S-1.25C
• Crimping contact: Hirose DF13-2630SCFA
It is also possible to source pre-crimped cables from catalog distributors such as Digi-Key.
silabs.com | Building a more connected world. Rev. 1.1 | 22
UG309: Thunderboard Sense 2 User's Guide
Debugging
4. Debugging
The Thunderboard Sense 2 contains an on-board, fully functional SEGGER J-Link Debugger that interfaces to the target EFR32MG12
using the Serial Wire Debug (SWD) interface. The debugger allows the user to download code and debug applications running in the
target EFR32MG12. Additionally, it also provides a virtual COM port (VCOM) to the host computer that is directly connected to the target device's serial port for general purpose communication between the running application and the host computer.
An external Silicon Labs debugger can also be used with the board by connecting it to the Mini Simplicity connector. This allows advanced debugging features as described in section 4.3 Mini Simplicity Connector. A Silicon Labs Wireless Starter Kit (WSTK) is a good
example of a debugger that can be used with the Thunderboard Sense 2 when connected through a debug adapter.
The figure blow shows the possible debug options.
Important: When connecting an external debugger that sources voltage to the VMCU net, the USB and battery power sources must
be removed. Failure to do so will create power conflicts and erroneous current measurements with AEM.
Figure 4.1. Thunderboard Sense 2 Debugging Possibilities
4.1 On-board Debugger Considerations
The on-board debugger is a SEGGER J-Link debugger running on an EFM32 Giant Gecko. The debugger is directly connected to the
SWD and VCOM pins of the target EFR32MG12.
When the USB cable is inserted, the on-board debugger is automatically active and takes control of the SWD and VCOM interfaces.
This means that serial wire debug and communication will not work with an external WSTK connected through the Mini Simplicity Connector at the same time. The on-board LDO is also activated, which then powers the board.
When the USB cable is removed, the on-board debugger goes into a very low power shutoff mode (EM4S), consuming around 20 nA
typically. This means that an application running off batteries does not need to worry about the power consumption of the on-board
debugger. Since the I/O voltage rail of the debugger remains powered in the battery operated mode, the pins connected to the SWD
and VCOM interfaces maintain proper isolation and prevent leakage currents.
silabs.com | Building a more connected world. Rev. 1.1 | 23
UG309: Thunderboard Sense 2 User's Guide
Debugging
4.2 Virtual COM Port
The virtual COM port is a connection to a USART of the target EFR32MG12, and allows serial data to be sent and received from the
device. The on-board debugger presents this as a virtual COM port on the host computer that shows up when the USB cable is inserted. Alternatively, the VCOM port can also be used through the Mini Simplicity Connector with an external WSTK.
Data is transferred between the host computer and the debugger through the USB connection, which emulates a serial port using the
USB Communication Device Class (CDC). From the debugger, the data is passed on to the target device through a physical UART
connection.
The serial format is 115200 bps, 8 bits, no parity, and 1 stop bit. The current firmware does not support changing the baud rate.
Using the VCOM port through the Mini Simplicity Connector with an external WSTK works in a similar way, but requires that the onboard debugger is unplugged. The board controller on the WSTK then makes the data available over USB (CDC) or an IP socket.
Note: Changing the baud rate for the COM port on the PC side does not influence the UART baud rate between the debugger and the
target device.
4.3 Mini Simplicity Connector
The Mini Simplicity connector is a 10-pin 1.27 mm pitch connector that gives access to advanced debugging features. Debugging with
an external WSTK allows:
• Debugging of the target device through SWD
• Communication using the VCOM port
• Packet Trace Interface
• Advanced Energy Monitor
Note that the Mini Simplicity Connector cannot be used at the same time as the on-board debugger is active (USB cable is plugged in).
For information on how to correctly connect to the kit, see Figure 4.1 Thunderboard Sense 2 Debugging Possibilities on page 23. The
recommended way to power the board when using the Mini Simplicity Connector is to use the AEM voltage supply of the WSTK. Power-cycling of the board, if necessary, can easily be done by flipping the power switch on the WSTK to "BAT" and back to "AEM".
It is also possible to have the Thunderboard Sense 2 powered by a battery and still use the Mini Simplicity Connector for debugging
and communication. In this case, the power switch on the WSTK must be set to the "BAT" position, to prevent a power conflict. In this
case, level shifters on the WSTK itself takes care of interfacing to different voltage levels on the Thunderboard Sense 2.
silabs.com | Building a more connected world. Rev. 1.1 | 24
5. Radio
GND
GND
GND GND
GND
GND
RFVDD
GND
GND
PAVDD
GND GND
GND GND
C4
220N
L4
742692004
1 2
C3
10P
L1
2N2
C1
1P5
L2
1N8
RF Analog Power
PA Power
Ground
RF I/ORF Crystal
U1B
HFXTAL_N
K1
HFXTAL_P
L1
PAVDD
M8
PAVDD
N8
PAVSS
M6
PAVSS
M7
RFVDD
J1
RFVDD
J2
RFVSS
H5
RFVSS
H6
RFVSS
H7
RFVSS
H8
RFVSS
H9
RFVSS
J5
RFVSS
J6
RFVSS
J7
RFVSS
J8
RFVSS
J9
RFVSS
K2
RFVSS
L2
RFVSS
M2
RFVSS
M3
RFVSS
M4
RFVSS
M5
RFVSS
N5
RFVSS
G7
RFVSS
E5
RFVSS
E6
RFVSS
E7
RFVSS
E8
RFVSS
E9
RFVSS
F5
RFVSS
F6
RFVSS
F7
RFVSS
F8
RFVSS
F9
RFVSS
G5
RFVSS
G6
RFVSS
G8
RFVSS
G9
2G4RF_ION
N6
NC
N1
NC
N3
NC
N4
NC
N2
2G4RF_IOP
N7
C5
10P
ANT1
2450AT18D0100
GND
2
IN
1
GND
3
GND
4
X1
38.4 MHz
31
2
4
C6
NM
C2
100P
L3
742692004
1 2
R110
0R
C20
1P5
2.4 GHz
Matching
Network
Chip Antenna and
Antenna Matching Network
Supply
Filtering
High
Frequency
Crystal
EFR32
5.1 RF Section
This section gives a short introduction to the RF section of the BRD4166A board.
The schematic of the RF section is shown in the figure below.
UG309: Thunderboard Sense 2 User's Guide
Radio
Figure 5.1. Schematic of the RF Section
5.1.1 Description of the RF Matching
The impedance of the RF port of the EFR32MG12 is matched to 50 Ohm: the 2G4RF_ION pin is connected to ground while the
2G4RF_IOP pin is connected to a two-element impedance matching circuitry. The on-board ceramic antenna is also matched to
50 Ohm by its impedance matching components and connected to the EFR32MG12 through an optional 0 Ohm resistor.
5.1.2 RF Section Power Supply
On the BRD4166A, the supply for the radio (RFVDD) and the power amplifier (PAVDD) is connected to the on-chip dc-dc converter. By
default, the dc-dc converter provides 1.8 V for the entire RF section (for details, see the schematic of the BRD4166A).
5.1.3 RF Matching Bill of Materials
The Bill of Materials of the BRD4166A RF matching network is shown in the following table.
Component name Value Manufacturer Part Number
C6 (optional) 10 pF Murata GRM0335C1E100JA01
silabs.com | Building a more connected world. Rev. 1.1 | 25
L1 2.2 nH Murata LQP03TN2N2B02D
C1 1.5 pF Murata GRM0335C1E1R5CD01
Table 5.1. Bill of Materials of the BRD4166A RF Matching Network
UG309: Thunderboard Sense 2 User's Guide
Radio
5.1.4 Antenna
The BRD4166A has an on-board ceramic antenna.
The land pattern for the antenna on the PCB layout was designed based on the recommendations of the antenna data sheet. Because
there is significant difference between the layout (practically the board size) of the BRD4166A and the antenna evaluation board, the
applied antenna matching network deviates from the recommendation.
The values of the antenna matching network were fine-tuned to match the antenna impedance close to 50 Ohm on the BRD4166A
PCB. The resulting antenna impedance and reflection are shown in the figure below.
Figure 5.2. Fine-tuned Antenna Impedance (Red Curve) and Reflection (Blue Curve)
5.1.5 Antenna Matching Bill of Materials
The Bill of Materials of the BRD4166A antenna matching network is shown in the following table.
Table 5.2. Bill of Materials of the BRD4166A Antenna Matching Network
Component name Value Manufacturer Part Number
ANT1 - Johanson 2450AT18D0100
L2 3.9 nH Murata LQP03TN1N8B02D
C20 1.5 pF Murata GRM0335C1E1R5BA01D
silabs.com | Building a more connected world. Rev. 1.1 | 26
UG309: Thunderboard Sense 2 User's Guide
Radio
5.2 EMC Regulations for 2.4 GHz
5.2.1 ETSI EN 300-328 Emission Limits for the 2400-2483.5 MHz Band
Based on ETSI EN 300-328, the allowed maximum fundamental power for the 2400-2483.5 MHz band is 20 dBm EIRP. For the unwanted emissions in the 1 GHz to 12.75 GHz domain, the specified limit is -30 dBm EIRP.
5.2.2 FCC15.247 Emission Limits for the 2400-2483.5 MHz Band
FCC 15.247 allows conducted output power up to 1 Watt (30 dBm) in the 2400-2483.5 MHz band. For spurious emissions the limit is
-20 dBc based on either conducted or radiated measurement, if the emission is not in a restricted band. The restricted bands are specified in FCC 15.205. In these bands, the spurious emission levels must meet the levels set out in FCC 15.209. In the range from
960 MHz to the frequency of the 5th harmonic, it is defined as 0.5 mV/m at 3 m distance (equals to -41.2 dBm in EIRP).
In case of operating in the 2400-2483.5 MHz band, the 2nd, 3rd, and 5th harmonics can fall into restricted bands so apply the dBm for
those bands. For the 4th harmonic, the -20 dBc limit should be applied.
5.2.3 Applied Emission Limits
The FCC restricted band limits are radiated limits only. Additionally, Silabs applies these limits to the conducted spectrum. In other
words, it is assumed that, for custom boards, an antenna with 0 dB gain at the fundamental and the harmonic frequencies is applied. In
that theoretical case, based on the conducted measurement, compliance with the radiated limits can be estimated.
The overall applied limits are shown in the table below.
Table 5.3. Applied Limits for Spurious Emissions
Harmonic Frequency Limit
2nd 4800~4967 MHz -41.2 dBm
3rd 7200~7450.5 MHz -41.2 dBm
4th 9600~9934 MHz -30 dBm
5th 12000~12417.5 MHz -41.2 dBm
silabs.com | Building a more connected world. Rev. 1.1 | 27
Y
X
Z
UG309: Thunderboard Sense 2 User's Guide
Radio
5.3 Radiated Power Measurements
The output power of the EFR32MG12 was set to 10 dBm. The board was supplied through its USB connector by connecting to a PC
through a USB cable.
During the measurements the board was rotated in three cuts, see the reference plane illustration in the figure below. The radiated
powers of the fundamental and the harmonics were measured with horizontal and vertical reference antenna polarizations.
Figure 5.3. DUT Reference Planes
5.3.1 Maximum Radiated Power Measurement
The measured maximums of the fundamental and the harmonics are shown in the table below.
Table 5.4. Maximums of the Measured Radiated Powers of BRD4166A
2.405 GHz EIRP [dBm] Orientation Margin [dB] Limit in EIRP [dBm]
Fundamental 10.1 YZ/H 19.9 30
2nd harmonic -47.5 XY/H 6.3 -41.2
3rd harmonic
4th harmonic
5th harmonic
* Signal level is below the Spectrum Analyzer noise floor.
As shown, the levels of the harmonics are far below the applied limit.
<-50
<-50
<-50
*
*
*
-/- >10 -41.2
-/- >20 -30
-/- >10 -41.2
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5.3.2 Antenna Pattern Measurement
The measured typical antenna patterns are shown in the figures below.
UG309: Thunderboard Sense 2 User's Guide
Radio
Figure 5.4. Antenna Pattern - XY
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UG309: Thunderboard Sense 2 User's Guide
Radio
Figure 5.5. Antenna Pattern - XZ
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UG309: Thunderboard Sense 2 User's Guide
Radio
Figure 5.6. Antenna Pattern - YZ
5.4 EMC Compliance Recommendations
5.4.1 Recommendations for 2.4 GHz ETSI EN 300-328 Compliance
As it was shown in the previous chapter with the EFR32MG12 output power set to 10 dBm, the radiated power of the fundamental of
the BRD4166A complies with the 20 dBm limit of the ETSI EN 300-328. The harmonic emissions are under the -30 dBm limit with large
margin.
5.4.2 Recommendations for 2.4 GHz FCC 15.247 Compliance
As it was shown in the previous chapter with the EFR32MG12 output power set to 10 dBm, the radiated power of the fundamental of
the BRD4166A complies with the 30 dBm limit of the FCC 15.247. The harmonic emissions are under the applied limits with large margin.
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UG309: Thunderboard Sense 2 User's Guide
Schematics, Assembly Drawings and BOM
6. Schematics, Assembly Drawings and BOM
The schematics, assembly drawings, and bill of materials (BOM) for the hardware included on the Thunderboard Sense 2 are available
through Simplicity Studio when the kit documentation package has been installed.
silabs.com | Building a more connected world. Rev. 1.1 | 32
SLTB004A
Thunderboard Sense 2
1632000360
25-03-20
B05
UG309: Thunderboard Sense 2 User's Guide
Kit Revision History and Errata
7. Kit Revision History and Errata
7.1 Revision History
The kit revision can be found printed on the box label of the kit, as outlined in the figure below. The kit revision history is summarised in
Table 7.1 Kit Revision History on page 33.
Figure 7.1. Revision Info
Table 7.1. Kit Revision History
Kit Revision Released Description
B05 25 March 2020 Updated to BRD4166A Rev. D03.
B04 8 January 2020 Updated to BRD4166A Rev. D02.
B03 26 November 2019 Replaced Get-started card.
B02 6 November 2019 Added Thread Certified Sticker.
B01 12 April 2018 Updated to BRD4166A Rev. D01.
B00 26 September 2017 Updated to BRD4166A Rev. D00.
A01 10 August 2017 Initial version.
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UG309: Thunderboard Sense 2 User's Guide
Board Revision History and Errata
8. Board Revision History and Errata
8.1 Revision History
The board revision can be found laser printed on the board, and the board revision history is summarised in Table 8.1 Board Revision
History on page 34.
Table 8.1. Board Revision History
Revision Released Description
D03 25 March 2020 Changed crystals and updated the matching network to achieve better band-
width.
D02 7 January 2020 Change EOL J-Link LED.
D01 17 December 2017 Updated EFR32MG12 to Rev. C.
D00 26 September 2017 Updated Si7210 revision. Changed IMU to ICM-20648.
C00 4 April 2017 Initial version.
8.2 Errata
Table 8.2. Board Errata
Board Revision Problem Description
C00 Si7210 Errata The rev. C00 boards were fitted with an early revision A of the Si7210 Hall Ef-
fect Sensor. This version has an issue where a large negative field measurement turns positive.
C00 IMU draws additional cur-
rent
The rev. C00 boards were fitted with an ICM-20948 instead of an ICM-20648.
This results in an additional current draw when the IMU is enabled and the supply voltage VMCU is above 1.8 V.
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UG309: Thunderboard Sense 2 User's Guide
Document Revision History
9. Document Revision History
Revision 1.1
August, 2020
Updated kit and board revision history. Added information about PTI in section 3.7. Removed note about the on-board debugger issuing
a reset at startup as this is no longer true with firmware release 1.42 and up. Removed sentence about current firmware not supporting
flow control on VCOM as this is now supported.
Revision 1.0
September, 2017
Initial document version.
silabs.com | Building a more connected world. Rev. 1.1 | 35
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