• EFR32 Mighty Gecko Wireless SoC
• Fine grained power-control for ultra low
power operation
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The board is a small and cost effective, feature rich, prototype and development platform based on the EFR32™ Mighty Gecko Wireless System-on-Chip. The Thunderboard Sense is an ideal platform for developing energy-friendly connected IoT devices.
This is a true multi-protocol capable kit, supporting proprietary stacks and standard protocols such as Zigbee, Thread and Bluetooth® low energy.
KEY POINTS
D
The Thunderboard™ Sense is the ultimate multi-sensor, multiprotocol cloud inspiration kit.
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UG250: Thunderboard Sense User's Guide
The Thunderboard Sense 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.
• Six sensors and four high brightness
controllable RGB LEDs
• User LEDs/pushbuttons
• 8-Mbit Flash for OTA programming
• SEGGER J-Link on-board debugger
• Virtual COM Port
• Mini Simplicity connector for AEM and
packet trace using 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
• Indoor air quality gas sensor
• 6-axis inertial sensor
• Barometric pressure sensor
• MEMS microphone
SOFTWARE SUPPORT
• Simplicity Studio™
• Energy Profiler
• Network Analyzer
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A built in SEGGER J-Link debugger ensures easy customization and development.
• 2.4 GHz ceramic chip antenna
silabs.com | Building a more connected world.
Rev. 1.1
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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1.2 Hardware Content
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1.3 Kit Hardware Layout.
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1.1 Kit Contents
2. Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Absolute Maximum Ratings .
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2.2 Recommended Operating Conditions .
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2.3 Current Consumption .
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3.1 Block Diagram.
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3.2 Power Supply .
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3.3 EFR32 Reset .
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3.4 Peripheral Power Domains
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3. Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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3.5 Sensors . . . . . . . . . . . . . . . . .
3.5.1 Si7021 Relative Humidity and Temperature Sensor
3.5.2 Si1133 UV Index and Ambient Light Sensor . . .
3.5.3 BMP280 Barometric Pressure Sensor . . . . .
3.5.4 CCS811 Indoor Air Quality Gas Sensor . . . .
3.5.5 ICM-20648 6-Axis Inertial Sensor . . . . . .
3.5.6 SPV1840 MEMS Microphone . . . . . . .
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3.6 LEDs . . . . . . . . . .
3.6.1 RGB LEDs . . . . . .
3.6.2 Low power red/green LED.
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.18
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3.7 Push Buttons .
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3.10 Connectors . . . . . . .
3.10.1 Breakout Pads . . . .
3.10.2 Mini Simplicity Connector
3.10.3 USB Micro-B Connector .
3.10.4 Battery Connector . . .
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.20
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4. Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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3.8 Memory .
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3.9 On-board Debugger .
4.1 On-board Debugger .
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.23
4.2 Virtual COM Port .
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.24
4.3 Mini Simplicity Connector .
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.24
5. Power and Interrupt Controller . . . . . . . . . . . . . . . . . . . . . . . .
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5.1 Communication .
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.25
5.2 Register Map .
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.26
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silabs.com | Building a more connected world.
Rev. 1.1 | 2
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.28
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6. Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
6.1 RF Section . . . . . . . . . .
6.1.1 Description of the RF Matching .
6.1.2 RF Section Power Supply . . .
6.1.3 RF Matching Bill of Materials . .
6.1.4 Antenna . . . . . . . . .
6.1.5 Antenna Matching Bill of Materials
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6.3 Radiated Power Measurements . . . . . .
6.3.1 Maximum Radiated Power Measurement
6.3.2 Antenna Pattern Measurement . . . .
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6.4 EMC Compliance Recommendations . . . . . . . . . . .
6.4.1 Recommendations for 2.4 GHz ETSI EN 300-328 Compliance
6.4.2 Recommendations for 2.4 GHz FCC 15.247 Compliance . .
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.36
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7. Schematics, Assembly Drawings and BOM . . . . . . . . . . . . . . . . . . .
37
8. Kit Revision History and Errata
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38
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6.2 EMC Regulations for 2.4 GHz . . . . . . . . . . . . . .
6.2.1 ETSI EN 300-328 Emission Limits for the 2400-2483.5 MHz Band
6.2.2 FCC15.247 Emission Limits for the 2400-2483.5 MHz Band . .
6.2.3 Applied Emission Limits . . . . . . . . . . . . . .
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5.3 Interrupt Controller . . . . .
5.3.1 Clearing Interrupts . . .
5.3.2 Periodic Event Signalling .
8.1 Revision History .
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8.2 Errata
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.38
9. Board Revision History and Errata . . . . . . . . . . . . . . . . . . . . . .
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10. Document Revision History
silabs.com | Building a more connected world.
Rev. 1.1 | 3
UG250: Thunderboard Sense User's Guide
Introduction
1. Introduction
The Thunderboard Sense (OPN: SLTB001A) has been designed to inspire customers to make battery operated IoT devices with the
Silicon Labs EFR32 Mighty Gecko Wireless System-on-Chip. The highlights of the board include six different environmental sensors
and four high brightness RGB LEDs accessible to the EFR32 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.
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Programming the Thunderboard Sense 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 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 for more information about debugging and programming interfaces that can
be used with Silicon Labs' starter kits.
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Connecting external hardware to the Thunderboard Sense can be done using the 20 breakout pads which present peripherals from the
EFR32 Mighty Gecko such as I2C, SPI, UART and GPIOs. The breakout pads follow the same pinout as the expansion headers (EXP)
on other Silicon Labs Starter Kits.
silabs.com | Building a more connected world.
Figure 1.1. Thunderboard Sense
Rev. 1.1 | 4
UG250: Thunderboard Sense User's Guide
Introduction
1.1 Kit Contents
The following items are included in the box:
• 1x Thunderboard Sense board (BRD4160A)
1.2 Hardware Content
1.3 Kit Hardware Layout
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The layout of the Thunderboard Sense is shown below.
EFR32
Mighty Gecko
2.4 GHz
Chip Antenna
RGB LED
EFM8 Power and
Interrupt Controller
Top View
BMP280 Pressure
Sensor
3
5
EXP
2
4
om
20-pin EXP-header
breakout pads
8
9
10
11
12
13
14
15
17
RESET
19
EXP
RGB LED
Bottom View
SPV1840 MEMS
Microphone
Si1133 Ambient Light
On-board USB
& UV Sensor
J-Link Debugger
Mini-Simplicity
Connector
16
18
45 mm
External Battery
Connector
20
Si7021 Humidity and
Temperature Sensor
R
Reset Button
RGB LED
Push Button 0
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ICM-20648
6-axis Intertial Sensor
30 mm
Acoustic hole
1
CCS881 Indoor
Air Quality Sensor
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The following key hardware elements are included on the Thunderboard Sense:
• EFR32 Mighty Gecko Wireless SoC with a 2.4 GHz ceramic antenna for wireless transmission
• Power and interrupt controller for fine grained power-control based on a Silicon Labs EFM8 Sleepy Bee microcontroller
• Silicon Labs Si7021 Relative Humidity and Temperature Sensor
• Silicon Labs Si1133 UV Index and Ambient Light Sensor
• Bosch Sensortec BMP280 Barometric Pressure Sensor
• Cambridge CMOS Sensors CCS811 Indoor Air Quality Gas Sensor
• InvenSense ICM-20648 6-Axis Inertial Sensor
• Knowles SPV1840 MEMS Microphone
• Four high brightness RGB LEDs, one bi-color LED and two push buttons
• Macronix Ultra Low Power 8-Mbit SPI Flash (MX25R8035F)
• On-board SEGGER J-Link debugger for easy programming and debugging, and with a virtual COM port through the USB Micro-B
connector
• Mini Simplicity connector for access to energy profiling and advanced wireless network debugging
• Breakout pads for connection to external hardware
• Reset button and automatic switchover between USB and battery power
• CR2032 coin cell connector and external battery connector
Push Button 1
USB Micro-B Connector
- Virtual COM port
- Debug access
CR2032 Coin Cell
Connector
RGB LED
Figure 1.2. Thunderboard Sense Hardware Layout
silabs.com | Building a more connected world.
Rev. 1.1 | 5
UG250: Thunderboard Sense User's Guide
Specifications
2. Specifications
2.1 Absolute Maximum Ratings
Symbol
Min
USB Input Voltage
VUSB-MAX
Supply Voltage VMCU
VVDDMAX
LDO output current
IVREG-LOAD
Voltage on any I/O pin
VDIGPIN
Current per I/O pin (sink)
IIOMAX
Current per I/O pin (source)
IIOMAX
Current for all I/O pins (sink)
IIOALLMAX
Current for all I/O pins (source)
IIOALLMAX
Storage Temperature
Tstg
ESD Susceptibility HBM (Human Body Model)
VESD
Unit
0
+5.5
V
0
+3.8
V
300
mA
VMCU+0.3
V
50
mA
50
mA
200
mA
200
mA
+85
˚C
2
kV
D
-0.3
-40
Symbol
Min
Typ
Max
Unit
VUSB
+4.5
+5.0
+5.5
V
VVBAT
+2.0
+3.8
V
+3.8
V
+3.6
V
70
˚C
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Parameter
Max
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2.2 Recommended Operating Conditions
Supply Input Voltage
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Supply Input Voltage
Supply Input Voltage (VMCU supplied externally)
VVMCU
+2.0
LDO Output Voltage
VREG
+3.0
TOP
0
+3.3
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Operating Temperature
Typ
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Parameter
silabs.com | Building a more connected world.
Rev. 1.1 | 6
UG250: Thunderboard Sense 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.
Table 2.1. Current Consumption, all values at 25˚C and VMCU = 3.3 V
Symbol
IEFR32
EFR32 Current Consumption 1
Condition
Min
EFR32 in EM0 Active mode
Radio in receive mode
Radio transmitter active @ 8 dBm
ISi7021
om
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Microphone Current Consumption
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R
CCS811 Current Consumption 9
silabs.com | Building a more connected world.
ICCS811
mA
23.3
mA
0.25
µA
Enabled, all sensors in standby 4
0.29
1.2
µA
Standby
0.125
µA
ADC Conversion in Progress
0.525
µA
Responding to commands and calculating results
4.25
mA
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
0.1
0.3
µA
1 Hz forced mode, pressure & temperature, lowest power
2.8
4.2
µA
Peak current during pressure measurement
0.72
1.12
mA
Current at temperature measurement
0.33
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IBMP280 Sleep current
IMIC
8.7
nA
Peak IDD during I2C operations
Barometric Pressure Sensor Current Consumption 7
mA
15
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RH/Temp Sensor Current Consumption 6
ISi1133
Unit
0.3
Turned off and isolated (leakage) 3
fo
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UV/ALS Current Consumption 5
IENV
Max
3.4
D
EFR32 in EM4S, all power domains disabled 2
Environmental Sensor Group Current
Consumption
Typ
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Parameter
Turned off
mA
50
nA
0.37
mA
Enabled, not sampling 8
0.20
Sampling @ 1 kHz with EFR32 in EM2 2
0.28
mA
Sampling @ 16 kHz with EFR32 in EM2 2
1.44
mA
Turned off and isolated (leakage) 3
0.3
15
nA
Enabled, sleep mode
3
µA
During measurement
20
mA
0.67
mA
Average for a measurement every 60
seconds
Rev. 1.1 | 7
UG250: Thunderboard Sense User's Guide
Specifications
Parameter
Symbol
IIMU
IMU Current Consumption 10
Condition
Min
Turned off and isolated (leakage) 3
IRGB
mA
Accelerometer only, 102.3 Hz update rate
68.9
µA
1.27
Turned off
0.1
mA
0.3
µA
µA
10
µA
29.9
mA
D
65
80
nA
0.54
mA
USB cable inserted, current sourced from
USB 5V
29
mA
USB cable removed, current sourced
from VMCU rail.
20
nA
N
ew
Idle
fo
r
Awake, responding to I2C commands
IDBG
nA
1.23
Current per LED, all colors 100% duty cycle
On-board Debugger Current Consumption
25
Gyroscope Only, 102.3 Hz update rate
Additional current for each enabled LED
IPIC
0.5
µA
Power Enabled, all LEDs off
Power and Interrupt Controller 2
Unit
8
Gyroscope + Accelerometer, 102.3 Hz
update rate
RGB LED Current Consumption
Max
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Full-chip sleep mode
Typ
From EFR32 Mighty Gecko SoC datasheet
2
Measured with advanced energy monitor (AEM) using a Wireless Starter Kit (WSTK)
3
From TS3A4751 datasheet
4
Combination of UV/ALS, RH/Temp and BMP sensors' sleep currents
5
From Si1133 datasheet
6
From Si7021-A20 datasheet
7
From BMP280 datasheet
8
Based on microphone, OP-AMP and LDO datasheets
9
From CCS811 datasheet
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1
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10 From ICM-20648 datasheet
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Rev. 1.1 | 8
UG250: Thunderboard Sense User's Guide
Hardware
3. Hardware
The core of the Thunderboard Sense is the EFR32 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 EFR32. The user interface components
include push buttons, a bi-colour LED and four high brightness RGB LEDs.
An overview of the Thunderboard Sense is illustrated in the figure below.
Device Connectivity & Debugging
USB Micro-B
Connector
Mini-Simplicity Breakout Pads
(EXP-Header pinout)
Connector
N
ew
J-Link
Debugger
D
3.1 Block Diagram
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The key aspects of the hardware will be explained in this chapter, while in-depth information on the EFR32 Mighty Gecko SoC can be
found in the EFR32MG datasheet and reference manual. For placement and layout of the hardware components the reader is referred
to 1.3 Kit Hardware Layout.
Radio
Memory
2.4 GHz
Antenna
8 Mbit
MX25R
fo
r
Serial Flash
EFM8
Sleepy Bee
m
en
de
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Power and Interrupt
Controller
Buttons and LEDs
User Buttons
& LEDs
EFR32MG
Wireless SoC
x4
RGB LEDs
Sensors
i7210
ec
Si1133
Temperature
& Humidity
Sensor
SPV1840
N
ot
R
Hall Effect
Sensor
om
Si7021
silabs.com | Building a more connected world.
Ambient
light & UV
Sensor
ICM-20648
MEMS
Microphone
6-axis Intertial
Sensor
CCS811
Indoor
Air Quality
Sensor
BMP280
Pressure
Sensor
Figure 3.1. Kit Block Diagram
Rev. 1.1 | 9
UG250: Thunderboard Sense 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 Power Options on page 10 shows the power options available on the kit and illustrates the main system
power architecture.
Automatic
Switchover
Battery
3V3
IN
OUT
Peripherals
LDO
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EFR32MG
Wireless SoC
Peripherals
Peripherals
USB micro-B
D
5V0
VMCU
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Mini Simplicity
Connector
Peripherals
Figure 3.2. Thunderboard Sense Power Options
fo
r
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 volt power net on the USB bus is regulated down to 3.3 volt 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.
m
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Batteries can be connected to the Thunderboard Sense using either the CR2032 coin cell connector 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.
Note: Do not connect batteries to both the CR2032 coin cell connector and the external battery connector at the same time.
A third option for powering the Thunderboard Sense exists through the Mini Simplicity connector. This option requires that no other
power sources are present on the kit, as the power is injected directly to the VMCU power net. Powering the Thunderboard Sense
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. For more information about using the Mini Simplicity connector,
please refer to 4.3 Mini Simplicity Connector.
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Note: When powering the board through the Mini Simplicity connector, the USB and battery power sources must be removed.
R
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The power supply options are summarized in Table 3.1 Thunderboard Sense Power Options on page 10. For placement of the USB
and battery connectors the reader is referred to 1.3 Kit Hardware Layout.
Table 3.1. Thunderboard Sense Power Options
VIN
VMCU
3V3
5V0
USB power
4.5 - 5.5 V
On-board regulator
On-board regulator
USB VBUS
CR2032 battery
2.0 - 3.8 V
Battery voltage
Turned off and isolated
No voltage present
External battery
2.0 - 3.8 V
Battery voltage
Turned off and isolated
No voltage present
Mini Simplicity
2.0 - 3.8 V
Debugger dependent
Turned off and isolated
No voltage present
N
ot
Supply mode
silabs.com | Building a more connected world.
Rev. 1.1 | 10
UG250: Thunderboard Sense User's Guide
Hardware
3.3 EFR32 Reset
The EFR32 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.
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In addition to the reset sources mentioned above, the debugger will also issue a reset to the EFR32 when starting up. This means that
removing power to the debugger (unplugging the USB Micro-B cable) will not generate a reset, but plugging the cable back in will cause
a reset as the debugger starts up.
3.4 Peripheral Power Domains
D
The sensors that make up most of the peripheral set of the Thunderboard Sense are grouped into power domains that are turned off
when not in use. This allows for the lowest possible power consumption in every application. To help out with controlling the separate
power domains, a Silicon Labs EFM8 Sleepy Bee microcontroller is used as an on-board Power and Interrupt Controller. By default, all
sensors are disabled when the board powers up.
N
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The EFM8 Sleepy Bee comes pre-programmed with a simple register interface accessible over the I2C bus, which is used to enable
and disable power to the different sensors and the RGB LEDs on the board. It also contains a simple interrupt controller that aggregates interrupts from the sensors and notifies the host in case of interrupt events.
The EFM8 Sleepy Bee itself spends most of the time in sleep mode, and consumes very little power when doing so. In order for it to
respond to I2C commands, the device must first be woken up. The INT/WAKE pin (PD10) functions as a dual role interrupt/wake-up pin.
The EFR32 pulses this pin low to wake up the EFM8, and the EFM8 pulses the pin low to notify the host of interrupt events.
fo
r
More details on communication between the EFR32 and the power controller, as well as register map and information related to the
interrupt controller, can be found in 5. Power and Interrupt Controller.
The different power connections are illustrated in the figure below.
EFR32MG
EFR32MG
Analog
PC10 (I2C0_SCL#14)
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RGB
SPI bus
I2C bus
PC11 (I2C0_SDA#16)
Power & I2C
isolation
I2C_INT_WAKE
EFM8SB
EFM8SB
Individual enable signals
Temperature
& Humidity
Sensor
Ambient
light & UV
Sensor
CCS811
Indoor
Air Quality
Sensor
Power & SPI
isolation
ICM-20648
6-axis Intertial
Sensor
Power
isolation
Power
isolation
SPV1840
MEMS
Microphone
x4
RGB LEDs
BMP280
Pressure
Sensor
Figure 3.3. Power Domain Architecture
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Interrupt signals
Si1133
Si7021
Power & I2C
isolation
N
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3.5 Sensors
The Thunderboard Sense contains six different sensors which can be accessed from the EFR32 over the I2C and SPI interfaces.
•
•
•
•
•
•
Si7210
Effect
Silicon Labs Si7021 Relative Humidity & Temperature Hall
Sensor
Sensor
Silicon Labs Si1133 UV Index & Ambient Light Sensor
Bosch BMP280 Barometric Pressure Sensor
Cambridge CMOS Sensors CCS811 Indoor Air Quality Gas Sensor
InvenSense ICM-20648 6-axis Inertial Measurement Sensor
Knowles SPV1840LR5H-B MEMS Microphone
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Rev. 1.1 | 11
UG250: Thunderboard Sense User's Guide
Hardware
3.5.1 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.
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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.
EFR32MG
D
On the Thunderboard Sense, the Si7021 is powered down and isolated by default. To use the sensor, 0x01 must be written to the
ENV_SENSOR_CTRL register in the Power and Interrupt Controller, as described in 5. Power and Interrupt Controller. Doing so enables power to the Si7021 and connects the I2C lines used for the sensor to the main I2C bus. The Si7021 shares power and I2C bus
isolation switch with the Si1133 and BMP280 sensor, and hence, all these sensors are powered and connected to the main I2C bus
once 0x01 has been written to the ENV_SENSOR_CTRL register. The hardware connection is illustrated in Figure 3.3 Power Domain
Architecture on page 11 and Figure 3.4 Si7021 Relative Humidity and Temperature Sensor on page 12
VMCU
Si7021
PC10 (I2C0_SDA#15)
PD10 (Open drain GPIO)
I2C_SCL
ENV_SENSE_SCL
I2C_SDA
ENV_SENSE_SDA
I2C_INT_WAKE
Temperature
& Humidity
Sensor
0: I2C lines are isolated, sensor is not powered
1: Sensor is powered and connected
ENV_SENSE_ENABLE
m
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EFM8SB
fo
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PC11 (I2C0_SCL#15)
N
ew
VDD_ENV_SENSE
Figure 3.4. Si7021 Relative Humidity and Temperature Sensor
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Note: Due to self-heating from the on-board LDO, temperature measurements are slightly off when running off USB power. More accurate temperature measurements are achieved when powering the board with a battery or through the Mini Simplicity connector.
silabs.com | Building a more connected world.
Rev. 1.1 | 12
UG250: Thunderboard Sense User's Guide
Hardware
3.5.2 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.
EFR32MG
EFR32MG
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On the Thunderboard Sense, the Si1133 is powered down and isolated by default. To use the sensor, 0x01 must be written to the
ENV_SENSOR_CTRL register in the Power and Interrupt Controller, as described in 5. Power and Interrupt Controller. Doing so enables power to the Si1133 and connects the I2C lines used for the sensor to the main I2C bus. The Si1133 shares power and I2C bus
isolation switch with the Si7021 and BMP280 sensor, and hence, all these sensors are powered and connected to the main I2C bus
once 0x01 has been written to the ENV_SENSOR_CTRL register. The Si1133 has furthermore an interrupt pin that can generate an
interrupt signal whenever a new sample is ready. There are several settings for handling the interrupt signal in the Power and Interrupt
Controller as explained in 5.3 Interrupt Controller. The hardware connection is illustrated in Figure 3.3 Power Domain Architecture on
page 11 and Figure 3.5 Si1133 UV and Ambient Light Sensor on page 13
VMCU
D
Si1133
VDD_ENV_SENSE
PC10 (I2C0_SDA#15)
PC10
(I2C0_SDA#15)
PD10
(Open
drain GPIO)
I2C_SCL
ENV_SENSE_SCL
I2C_SDA
N
ew
PC11 (I2C0_SCL#15)
ENV_SENSE_SDA
I2C_INT_WAKE
Ambient
light & UV
Sensor
0: I2C lines are isolated, sensor is not powered
1: Sensor is powered and connected
EFM8SB
ENV_SENSE_ENABLE
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UV_ALS_INT
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Figure 3.5. Si1133 UV and Ambient Light Sensor
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Rev. 1.1 | 13
UG250: Thunderboard Sense User's Guide
Hardware
3.5.3 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 provides 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.
EFR32MG
EFR32MG
VMCU
BMP280
PC10
(I2C0_SDA#15)
PD10
(Open
drain GPIO)
I2C_SCL
ENV_SENSE_SCL
I2C_SDA
ENV_SENSE_SDA
I2C_INT_WAKE
N
ew
PC10 (I2C0_SDA#15)
D
VDD_ENV_SENSE
PC11 (I2C0_SCL#15)
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On the Thunderboard Sense, the BMP280 is powered down and isolated by default. To use the sensor, 0x01 must be written to the
ENV_SENSOR_CTRL register in the Power and Interrupt Controller, as described in 5. Power and Interrupt Controller. Doing so enables power to the BMP280 and connects the I2C lines used for the sensor to the main I2C bus. The BMP280 shares power and I2C bus
isolation switch with the Si7021 and Si1133 sensor, and hence, all these sensors are powered and connected to the main I2C bus once
0x01 has been written to the ENV_SENSOR_CTRL register. The hardware connection is illustrated in Figure 3.3 Power Domain Architecture on page 11 and Figure 3.6 BMP280 Absolute Pressure Sensor on page 14.
Pressure
Sensor
0: I2C lines are isolated, sensor is not powered
1: Sensor is powered and connected
ENV_SENSE_ENABLE
m
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EFM8SB
N
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Figure 3.6. BMP280 Absolute Pressure Sensor
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Rev. 1.1 | 14
UG250: Thunderboard Sense User's Guide
Hardware
3.5.4 CCS811 Indoor Air Quality Gas Sensor
The CCS811 is a digital gas sensor solution for indoor air quality monitoring over the I2C interface. Gases that can be detected by the
CCS811 includes ethanol and hazardous gases such as carbon monoxide and a wide range of volatile organic compounds (VOCs).
On the Thunderboard Sense, the CCS811 is powered down and isolated by default. 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. Both are done by setting bits in the CCS_CTRL
register in the Power and Interrupt Controller. See 5. Power and Interrupt Controller for details.
EFR32MG
EFR32MG
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The CCS811 has furthermore an interrupt pin that can generate an interrupt signal whenever a new sample is ready. There are several
settings for handling the interrupt signal in the Power and Interrupt Controller as explained in 5.3 Interrupt Controller. The hardware
connection is illustrated in Figure 3.3 Power Domain Architecture on page 11 and Figure 3.7 CCS811 Indoor Air Quality and Gas Sensor on page 15.
VMCU
CCS811
PC10 (I2C0_SDA#15)
PC10
(I2C0_SDA#15)
PD10
(Open
drain GPIO)
I2C_SCL
CCS811_SCL
I2C_SDA
CCS811_SDA
I2C_INT_WAKE
N
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PC11 (I2C0_SCL#15)
D
VDD_CCS811
Indoor
Air Quality
Sensor
0: I2C lines are isolated, sensor is not powered
1: Sensor is powered and connected
EFM8SB
CCS811_ENABLE
CCS811_#WAKE
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CCS811_INT
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Figure 3.7. CCS811 Indoor Air Quality and Gas Sensor
silabs.com | Building a more connected world.
Rev. 1.1 | 15
UG250: Thunderboard Sense User's Guide
Hardware
3.5.5 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. Acceleration is detected independently along the X-, Y-, and Z- axes with 16-bit ADCs, in addition to the angular rates around the same axes. An integrated processor computes motion processing algorithms for ease of use and improved system power performance. The device supports both the SPI
and I2C interface.
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On the Thunderboard Sense, 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 3.8 Thunderboard Sense Spatial Orientation on
page 16.
Y
Z
N
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X
D
Pin 1 chip
identifier
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Figure 3.8. Thunderboard Sense Spatial Orientation
m
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On the Thunderboard Sense, the ICM-20648 is powered down and isolated by default. To use the sensor, 0x01 must be written to the
IMU_CTRL register in the Power and Interrupt Controller, as described in 5. Power and Interrupt Controller. Doing so enables power to
the ICM-20648 and connects the SPI lines used for the sensor to the main SPI bus. The SPI interface is shared between the
ICM-20648 and the SPI Flash, but uses separate chip select signals for the two devices. The ICM-20648 has an interrupt pin which,
when enabled, generates an interrupt signal whenever a new sample is ready. There are several settings for handling the interrupt signal in the Power and Interrupt Controller as explained in 5.3 Interrupt Controller. The hardware connection is illustrated in Figure
3.3 Power Domain Architecture on page 11 and Figure 3.9 ICM-20648 Six-axis Inertial Sensor on page 16.
VMCU
EFR32MG
PC8 (US1_CLK#11)
PC6 (US1_TX#11)
SPI_SCLK
IMU_SCLK
SPI_MOSI
IMU_MOSI
SPI_MISO
IMU_MISO
om
PC7 (US1_RX#11)
PA5 (GPIO)
PC11 (I2C0_SCL#15)
ec
PC10 (I2C0_SDA#15)
IMU_CS
SPI_CS_IMU
ICM-20648
6-axis Intertial
Sensor
I2C_SCL
0: SPI lines are isolated, sensor is not powered
1: Sensor is powered and connected
I2C_SDA
I2C_INT_WAKE
N
ot
R
PD10 (Open drain GPIO)
VDD_IMU
silabs.com | Building a more connected world.
EFM8SB
IMU_ENABLE
IMU_INT
Figure 3.9. ICM-20648 Six-axis Inertial Sensor
Rev. 1.1 | 16
UG250: Thunderboard Sense User's Guide
Hardware
3.5.6 SPV1840 MEMS Microphone
The SPV1840 is an omnidirectional MEMS microphone with high performance and low power consumption in a miniature 3.75 x 1.85 x
0.90 mm surface mount package. Included on the SPV1840 is an acoustic sensor, a low noise input buffer and an output amplifier. The
microphone is suitable in applications requiring excellent audio performance and RF immunity.
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The SPV1840 is placed on the bottom side of the Thunderboard Sense with an acoustic ventilation hole going through to the top side.
This hole lets sound waves travel unimpeded from the top side of the board to the acoustic port of the MEMS microphone located on
the back side of the component. The top side of the board should therefore be oriented against the sound source for best possible
performance. Following the microphone is a signal processing stage containing an amplifier with 32.1 dB gain (-40.2 V/V) and an active
first order low pass filter with a cut-off frequency of 10 kHz.
EFR32MG
VMCU
G = 32.1 dB
N
ew
PD10 (Open drain GPIO)
MIC
I2C_SCL
SHDN
I2C_SDA
I2C_INT_WAKE
1V8_MIC
VMCU
MEMS
Microphone
VDD
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PC11 (I2C0_SCL#15)
PC10 (I2C0_SDA#15)
SPV1840
Gain & Filter
fc = 10 kHz
PF7 (ADC)
D
On the Thunderboard Sense, the SPV1840 is powered down by default. To use the sensor, 0x01 must be written to the MIC_CTRL
register in the Power and Interrupt Controller, as described in 5. Power and Interrupt Controller. This turns on the low-dropout regulator
powering both the microphone and the signal processing stage. The analog microphone signal is transmitted to the ADC of the EFR32.
The hardware connection is illustrated in Figure 3.3 Power Domain Architecture on page 11 and Figure 3.10 SPV1840 MEMS Microphone on page 17
LDO
EFM8SB
MIC_ENABLE
EN
m
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0: Sensor is not powered
1: Sensor is powered
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Figure 3.10. SPV1840 MEMS Microphone
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Rev. 1.1 | 17
UG250: Thunderboard Sense User's Guide
Hardware
3.6 LEDs
The board contains one low power bi-color LED (red/green), and four high brightness RGB LEDs. The low power LED and the RGB
LEDs share the same I/O pins, but the RGB LEDs can be individually enabled/disabled through the Power and Interrupt Controller.
Figure 3.11 LEDs on page 18 shows how the different LEDs are connected to the EFR32, and how power to the RGB LEDs is controlled.
The following sections contain more detailed information.
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VMCU
3.5 V
EFM8SB1
DC/DC
LED_POWER
EN
EFR32MG
LED_ENABLE[3:0]
PC10 (I2C0_SDA#15)
I2C_SCL
I2C_SDA
I2C_INT_WAKE
RGB_GREEN
PD12 (TIM0_CC1#19)
RGB_BLUE
PD13 (TIM0_CC2#19)
RED/GREEN
LED
LED_RED
RGB LED 2
RGB LED 3
Low-power
R/G LED
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LED_GREEN
RGB LED 1
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RGB LED 0
RGB_RED
PD11 (TIM0_CC0#19)
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PD10 (GPIO)
D
PC11 (I2C0_SCL#15)
Figure 3.11. LEDs
3.6.1 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).
om
The boost regulator and each LED is individually enabled by writing to the LED_CTRL register in the power domain and interrupt controller. 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.
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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 3.3V VMCU
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
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Color
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 | 18
UG250: Thunderboard Sense User's Guide
Hardware
3.6.2 Low power red/green LED
The board contains a small bi-color LED that is directly connected to PD11 and PD12 through current limiting resistors. Since these are
directly connected, they cannot be disabled, and will always light up when these lines are driven high.
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.
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Note: The pin that drives the green line of the RGB LEDs is connected to the red low-power LED, and the red line of the RGB LEDs is
connected to the green low-power LED.
3.7 Push Buttons
PC11 (I2C0_SCL#15)
PD14 (GPIO)
PC10 (I2C0_SDA#15)
PD15 (GPIO)
Push Button 0
Push Button 1
VMCU
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ew
VMCU
EFR32MG
EFR32MG
D
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.
GND
GND
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Figure 3.12. Push Buttons
3.8 Memory
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The Thunderboard Sense is equipped with an 8-Mbit Macronix SPI Flash that is connected directly to the EFR32 Mighty Gecko. Figure
3.13 Serial Flash on page 19 shows how the serial flash is connected to the EFR32. The SPI bus used for the flash is shared with the
ICM-20648 six-axis inertial sensor.
EFR32MG
PC8 (US1_CLK#11)
PC6 (US1_TX#11)
om
PC10 (US1_RX#11)
SPI_SCLK
SPI_MOSI
8 Mbit
MX25R
SPI_MISO
SPI_CS_FLASH
Serial Flash
Figure 3.13. Serial Flash
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PA4 (GPIO)
VMCU
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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 | 19
UG250: Thunderboard Sense User's Guide
Hardware
3.9 On-board Debugger
The Thunderboard Sense contains a microcontroller separate from the EFR32 Mighty Gecko that provides the user with a on-board JLink debugger through the USB micro-B port. This microcontroller is referred to as the "On-board Debugger", and is not programmable
by the user.
In addition to providing code download and debug features, the on-board debugger also presents a virtual COM port for general purpose application serial data transfer.
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Figure 3.14 On-Board Debugger Connections on page 20 shows the connections between the target EFR32 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. Please
refer to chapter 4. Debugging for more details on debugging.
Mini Simplicity
Connector
D
EFR32MG
EFR32MG
VCOM_TX
VCOM_RX
USB
On-Board
J-Link
Debugger
PA0 (UART_TX)
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Host
PC
PA1 (UART_RX)
DBG_SWCLK
PF0 (DBG_SCLK)
DBG_SWDIO
PF1 (DBG_SWDIO)
DBG_SWO
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(I2C0_SCL#15)
PF2PC11
(DBG_SWO)
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Figure 3.14. On-Board Debugger Connections
3.10 Connectors
Featured on the Thunderboard Sense is 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 Figure
3.15 Thunderboard Sense Connectors on page 20. For additional information on the connectors see the following sub chapters.
Expansion Header
Breakout
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Top Side
Battery Connector
(on reverse side)
1
2
EXP2 | VMCU
3
4
EXP4 | SPI_MOSI | PC6
6
EXP6 | SPI_MISO | PC7
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EXP1 | GND
EXP3 | UART_CTS | PA2
5
EXP7 | PF3
7
8
EXP8 | SPI_SCLK | PC8
EXP9 | PF4
9
10
EXP10 | SPI_CS | PC9
R
EXP5 | UART_RTS | PA3
12
EXP12 | UART_TX | PA0
14
EXP14 | UART_RX | PA1
15
16
EXP16 | I2C_SDA | PC10
EXP17 | BOARD_ID_SCL
17
18
EXP18 | 5V
EXP19 | BOARD_ID_SDA
19
20
EXP20 | 3V3
11
13
EXP15 | PC11 | I2C_SCL
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EXP11 | PF5
EXP13 | PF6
Mini-Simplicity
Connector
USB Micro-B
Connector
VBAT
GND
Hirose DF13C-2P-1.25V
Mini-Simplicity
Connector
VMCU
RST
VCOM_TX | PA0
SWDIO | PF1
PTI_FRAME | PB13
GND
VCOM_RX | PA1
SWO | PF2
SWCLK | PF0
PTI_DATA | PB12
Figure 3.15. Thunderboard Sense Connectors
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Rev. 1.1 | 20
UG250: Thunderboard Sense User's Guide
Hardware
3.10.1 Breakout Pads
20 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 of the board. The breakout
pads contain a number of I/O pins that can be used with most of the EFR32 Mighty Gecko's features. Additionally, the VMCU (main
board power rail), 3.3V (LDO regulator output) and 5V power rails are also exported.
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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
purpose 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. Table 3.3 Expansion Header Pinout on page 21 includes an overview of the expansion header and functionality that is shared with the kit.
Pin
Connection
EXP Header Function
Shared Feature
Right Side Breakout Pins
4
PC6
SPI_MOSI
6
PC7
SPI_MISO
8
PC8
SPI_SCLK
10
PC9
SPI_CS
12
PA0
UART_TX
14
PA1
UART_RX
16
PC10
I2C_SDA
18
5V
Board USB voltage
20
3V3
Board controller supply
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EFR32 voltage domain, included in AEM measurements.
IMU/SPI Flash
USART1_TX #11
IMU/SPI Flash
USART1_RX #11
IMU/SPI Flash
USART1_CLK #11
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VMCU
USART1_CS #11
Virtual COM Port
USART0_TX #0
Virtual COM Port
USART0_RX #0
Sensors/Power & Int. Controller
I2C0_SDA #15
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2
Peripheral Mapping
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Table 3.3. Expansion Header Pinout
Left Side Breakout Pins
GND
3
PA2
5
PA3
7
PF3
GPIO
9
PF4
GPIO
11
PF5
GPIO
PF6
GPIO
PC11
I2C_SCL
R
15
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13
Ground
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1
GPIO
Sensors/Power & Int. Controller
I2C0_SCL #15
BOARD_ID_SCL Connected to Board Controller for identification of add-on boards.
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17
GPIO
19
BOARD_ID_SDA Connected to Board Controller for identification of add-on boards.
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Rev. 1.1 | 21
UG250: Thunderboard Sense User's Guide
Hardware
3.10.2 Mini Simplicity Connector
The Mini Simplicity connector featured on the Thunderboard Sense 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 is described in
3.10.2 Mini Simplicity Connector.
Pin number
Connection
Function
1
VMCU
VAEM
2
GND
GND
3
EFR32 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
10
PB12
PTI_DATA
Description
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Target voltage on the debugged application. Supplied and monitored
by the AEM when power selection switch is in the "AEM" position.
Packet Trace Frame Signal
Packet Trace Data Signal
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3.10.3 USB Micro-B Connector
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Table 3.4. Mini Simplicity Connector Pin Descriptions
3.10.4 Battery Connector
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The USB port can be used for uploading code, debugging and as Virtual COM port, as described in 4. Debugging.
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).
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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 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.
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P/N for mating products:
• Single row socket, 2 pos: Hirose DF13-2S-1.25C
• Crimping contact: Hirose DF13-2630SCFA
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It is also possible to source pre-crimped cables from catalog distributors such as Digi-Key.
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Rev. 1.1 | 22
UG250: Thunderboard Sense User's Guide
Debugging
4. Debugging
The Thunderboard Sense contains an on-board fully functional SEGGER J-Link Debugger that interfaces to the target EFR32 using the
Serial Wire Debug (SWD) interface. The debugger allows the user to download code and debug applications running in the target
EFR32. 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.
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Figure 4.1 Thunderboard Sense Debugging Possibilities on page 23 show the possible debug options.
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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 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 when connected through a debug adapter.
Figure 4.1. Thunderboard Sense Debugging Possibilities
4.1 On-board Debugger
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 EFR32.
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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.
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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.
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Rev. 1.1 | 23
UG250: Thunderboard Sense User's Guide
Debugging
4.2 Virtual COM Port
The virtual COM port is a connection to a USART of the target EFR32, 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.
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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. Flow control signals RTS and CTS are provided, but not supported by
the current firmware implementation. The current firmware also 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.
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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
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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
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Please 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 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".
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It is also possible to have the Thunderboard Sense powered by a battery, and still use the 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.
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Rev. 1.1 | 24
UG250: Thunderboard Sense User's Guide
Power and Interrupt Controller
5. Power and Interrupt Controller
This chapter contains reference information about how to interface with the Power and Interrupt Controller implemented in the EFM8
Sleepy Bee on the Thunderboard Sense.
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The software examples available for the Thunderboard Sense provide a board support package (BSP) that handles enabling and interfacing to the different peripherals on the board. The BSP has supporting code to enable the different power domains, control the RGB
LEDs and enable interrupts in the interrupt controller. It is recommended to use the provided BSP to get up and running as quick as
possible with the kit.
5.1 Communication
Controlling the power domains and using the interrupt controller is done with commands over the I2C bus. The EFM8 firmware presents
a register interface that can be read and written by the EFR32.
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Before the Power and Interrupt Controller will respond to I 2C commands, it must first be woken up. The EFM8 wakes up and enables its
I2C peripheral on the falling edge of the int/wake pin (PD10). It remains awake as long as this line is low, and for about 1 ms after the
line goes high again. If there is activity on the I2C bus lines while it is awake, the timeout is extended until 1 ms after the activity stops.
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This means that the device can be woken up with just a short pulse on the int/wake pin. Please note that the minimum pulse width is
about 4 µs to ensure that the device properly wakes up. Several consecutive commands can be issued without re-asserting the wakeup pin as long as each transfer follows within 1 ms of the last.
Since the int/wake pin is used for both wake-up and interrupt signaling, it is recommended to configure the int/wake pin to an open drain
(wired AND) configuration to ensure that both devices can change the pin state.
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Writing to the registers is done by transmitting the 7-bit bus address 0x90 with the R/W bit cleared, followed by the register address and
the data to be written. Reading a register first requires the address pointer to be set up using an I2C write, followed by a new start and
the address with the R/W bit set. Reading can be done with a repeated start, or can be a simple one byte write followed by a read.
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SDA
SCL
INT/WAKE
Figure 5.1. I2C Register Write Example
Start
bit
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SDA
SCL
0
0
1
0
0
0
W ACK
0
0
0
0
0
0
0
1
Repeated
start bit
ACK
Register data: 0x01
I2C address 0x90 + Read bit
1
0
0
1
0
0
0
R
ACK
0
0
0
0
0
0
0
Stop
bit
1 NACK
Figure 5.2. I2C Register Read Example
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1
INT/WAKE
Register address 0x01
I2C address 0x90 + write bit
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Rev. 1.1 | 25
UG250: Thunderboard Sense User's Guide
Power and Interrupt Controller
5.2 Register Map
The register map of the power and interrupt controller is outlined below. Power to sensors are enabled by writing a single bit to the
control register for each sensor or sensor group. The CCS811 indoor air quality sensor has an additional "wake" bit that controls the
sensor's WAKE line. Control of the RGB LEDs consists of an enable bit for the on board regulator, and one bit for each of the four RGB
LEDs located on the board.
Addr
Name
Type
Reset
0x00
IMU_CTRL
RW
Control register for the inertial sensor
• Bits 7:1 - Reserved
• Bit 0 - Write 1 to this bit to enable power and SPI access
0x00
0x01
ENV_SENSOR_CTRL
RW
Environmental sensor group control register
• Bits 7:1 - Reserved
• Bit 0 - Write 1 to this bit to enable power and I2C access to the environmental sensor group
0x00
0x02
MIC_CTRL
RW
Microphone control register
• Bits 7:1 - Reserved
• Bit 0 - Write 1 to this bit to enable power to the microphone and microphone gain/filter circuit
0x00
0x03
CCS_CTRL
RW
Indoor air quality sensor control register
• Bits 7:2 - Reserved
• Bit 1 - Write 1 to this bit to wake up the indoor air quality sensor
• Bit 0 - Write 1 to this to enable power and I2C access to the indoor air
quality sensor
0x00
0x04
LED_CTRL
RW
Control register for the RGB LEDs
• Bits 7:4 - Individual enable bit for each RGB LED
• Bits 3:1 - Reserved
• Bit 0 - Write 1 to this bit to enable the RGB LED voltage regulator
0x00
0x05
INT_ENABLE
RW
Interrupt enable register
• Bits 7:3 - Reserved
• Bit 2 - UV_ALS interrupt enable
• Bit 1 - IMU interrupt enable
• Bit 0 - CCS811 interrupt enable
0x00
0x06
INT_CLEAR
W
Interrupt clear register
• Bits 7:3 - Reserved
• Bit 2 - Clears UV_ALS interrupt status flag
• Bit 1 - Clears IMU interrupt status flag
• Bit 0 - Clears CCS811 interrupt status flag
0x00
R
Interrupt status register
• Bits 7:3 - Reserved
• Bit 2 - UV_ALS interrupt status flag
• Bit 1 - IMU interrupt status flag
• Bit 0 - CCS811 interrupt status flag
0x00
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INT_STATUS
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0x07
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Description
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Table 5.1. Register Map
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Rev. 1.1 | 26
UG250: Thunderboard Sense User's Guide
Power and Interrupt Controller
Name
Type
Description
Reset
0x08
INT_CTRL
RW
Interrupt controller settings register
• Bits 7:6 - Reserved
• Bit 5 - Latched interrupt pin mode. If this bit is set the device will keep
the int/wake signal low as long as an enabled interrupt flag is set.
• Bit 4 - Periodic interrupt pulse enable. If this bit is set the device will
produce continuous pulses on the int/wake signal as long as an enabled interrupt flag is set.
• Bits 3:0 - Periodic interrupt pulse timer value. This bit field controls
the frequency of the periodic interrupt pulses.
0x00
0xF0
SYS_CMD
W
System command register
0x00
0xF1
VER_MAJOR
R
Firmware revision major
0xF2
VER_MINOR
R
Firmware revision minor
0xF3
VER_PATCH
R
Firmware revision patch
0xF4
SCRATCH0
RW
Scratch register 0
0xF5
SCRATCH1
RW
Scratch register 1
0xF6
SCRATCH2
RW
Scratch register 2
0xF7
SCRATCH3
RW
Scratch register 3
0xF8
DEVICE_ID0
RW
Device identification register 0
0x49
0xF9
DEVICE_ID1
RW
Device identification register 1
0x4F
0xFA
DEVICE_ID2
RW
Device identification register 2
0x58
0xFB
DEVICE_ID3
R
Device identification register 3
0x50
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Addr
0
0
0
0
0
0
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4
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UG250: Thunderboard Sense User's Guide
Power and Interrupt Controller
5.3 Interrupt Controller
A simple interrupt controller has been implemented in the EFM8 Sleepy Bee firmware to collect interrupt signals from several sources
and notify the host if something happens.
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The three different interrupt sources available are
• The inertial sensor (ICM-20648) interrupt
• The UV/ALS sensor (Si1133) interrupt
• The indoor air quality sensor (CCS811) interrupt
The interrupt controller always registers the falling edges of these three interrupt signals, and sets corresponding interrupt status flags
in the INT_STATUS register. If the corresponding enable bit is set in INT_ENABLE, the controller pulls INT/WAKE low for about 400 ns.
If the int/wake line happens to be pulled low by the EFR32 at the time an interrupt arrives, the interrupt controller defers generating the
pulse until a few µs after INT/WAKE goes high. This ensures that no interrupts are missed when the host is asserting the int/wake line
in order to communicate with the EFM8.
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The recommended procedure for asserting the int/wake pin when using interrupts is:
1. Disable falling edge interrupt on the int/wake pin (PD10)
2. Set the int/wake pin low
3. Wait minimum 4 µs (required to wake up the EFM8)
4. Enable falling edge interrupt on the int/wake pin
5. Release INT/WAKE so it gets pulled high externally
Re-enabling the interrupt before releasing the INT/WAKE allows any interrupts signalled by the interrupt controller right afterwards to be
caught.
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Figure 5.3 Interrupt Controller Example on page 28 shows an example of how the external interrupt events cause pulses on the int/
wake line when enabled.
IMU Interrupt
CCS811 Interrupt
UV/ALS Interrupt
INT/WAKE signal
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Example: INT_ENABLE = 0x03 (IMU & CCS811 interrupts enabled)
IMU event
signalled
CCS811 event
signalled
UV/ALS interrupt
disabled - event ignored
New IMU event
signalled
EFR32 pulls
int/wake low
Deferred CCS811
event signalled
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Figure 5.3. Interrupt Controller Example
5.3.1 Clearing Interrupts
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Clearing the interrupt status flags is done by writing 1 to the corresponding bits in the INT_CLEAR register, but interrupt flags can only
be cleared if they have been read from the INT_STATUS register. This ensures that no interrupt flags can be accidentally cleared without the host knowing they were set, if for example the interrupt occurs between reading the status register and clearing the flags.
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Note that interrupt status flags can only be cleared by writing to the INT_CLEAR register after reading INT_STATUS. If the external
interrupt line goes high again, the flag remains set until cleared. If another falling edge arrives, another interrupt pulse to the host will be
generated if the interrupt is enabled, regardless of the status flag value.
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Rev. 1.1 | 28
UG250: Thunderboard Sense User's Guide
Power and Interrupt Controller
5.3.2 Periodic Event Signalling
In some systems it could be possible that the interrupt pulse from the interrupt controller is missed, which can be critical to the application in some cases. As a possible work-around, there is a possibility to let the interrupt controller continuously signal pulses as long as
an interrupt that is enabled has its flag set. The idea being that if an interrupt is missed for some reason, one of the consecutive pulses
will be registered.
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Because this is very system and application dependent, it is necessary to choose an appropriate frequency for the interrupt pulses.
Slow systems expecting interrupts infrequently might need a longer repeat time than applications where the interrupt must be serviced
immediately. Since the application have to wait for the next pulse if an interrupt has been missed, this timing will influence the time it
takes for the application to respond to the event.
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The periodic pulses are enabled by setting bit 4 of the INT_CTRL register. The time between interrupt pulses is controlled by bits 3:0 of
the INT_CTRL register, with the formula shown below:
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For example, INT_CTRL[3:0] = 8 gives a pulse period of about 7.9 ms (about 126 Hz), while the lowest frequency is achieved with
INT_CTRL[3:0] = 15, which gives about 1 second (1 Hz). The shortest period is achieved by setting INT_CTRL[3:0] = 0, which gives an
interrupt period of 61 µs (about 16.4 kHz).
Figure 5.5 Periodic Event Signalling Example on page 29 shows an example of the interrupt pulse generation.
INT_STATUS
0x00
INT/WAKE signal
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IMU Interrupt
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INT_ENABLE = 0x02 (IMU interrupt enabled)
INT_CTRL
= 0x18 (periodic interrupt pulses enabled, tpulse = 7.9 ms)
0x02
tpulse
Periodic event
pulses signalled
0x00
EFR32 reads and clears
interrupt status flags
0x02
New IMU
interrupt
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Figure 5.5. Periodic Event Signalling Example
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Rev. 1.1 | 29
UG250: Thunderboard Sense User's Guide
Radio
6. Radio
6.1 RF Section
This section gives a short introduction to the RF section of the BRD4160A board.
The schematic of the RF section is shown in the figue below.
RF Crystal
10
3
2
4
RFVDD
GND
L3
CIM03U241
11
2G4RF_IOP
2G4RF_ION
C1
C20
10P
1P5
16
9
2
C2
C3
100P
10P
RFVSS
14
1
2
GND
PAVDD
PAVSS
GND
GND
C4
C5
220N
10P
GND
GND
TUNE
3
AMAN301512ST01
1N8
GND
D
L4
CIM03U241
15
L9
IN
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PAVDD
2
3N9
GND
PA Power
18
1
NM
Ground
RFVDD
ANT1
L2
GND
RF Analog Power
1
C6
17
2N2
HFXO
Chip Antenna and
Antenna Matching Network
L1
RF I/O
HFXI
X1
38.4 MHz
1
Supply
Filtering
2.4 GHz
Matching
Network
U1B
EFR32
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High
Frequency
Crystal
GND
Figure 6.1. Schematic of the RF section
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6.1.1 Description of the RF Matching
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The impedance of the RF port of the EFR32 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 EFR32 through an optional bypass capacitor.
6.1.2 RF Section Power Supply
On the BRD4160A 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 BRD4160A).
6.1.3 RF Matching Bill of Materials
The Bill of Materials of the BRD4160A RF matching network is shown in the following table.
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Table 6.1. Bill of Materials of the BRD4160A RF Matching Network
Value
Manufacturer
Part Number
L1
2.2 nH
Murata
LQP03TN2N2B02D
C1
1.5 pF
Murata
GRM0335C1E1R5CD01
C6 (optional)
10 pF
Murata
GRM0335C1E100JA01
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6.1.4 Antenna
The BRD4160A 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 datasheet. Due to the
fact that there is significant difference between the layout (practically the board size) of the BRD4160A and the antenna evaluation
board the applied antenna matching network deviates from the recommendation.
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The values of the antenna matching network were fine tuned to match the antenna impedance close to 50 Ohm on the BRD4160A
PCB. The resulting antenna impedance and reflection are shown in the figure below.
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Figure 6.2. Fine Tuned Antenna Impedance and Reflection
6.1.5 Antenna Matching Bill of Materials
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The Bill of Materials of the BRD4160A antenna matching network is shown in the following table.
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Table 6.2. Bill of Materials of the BRD4160A Antenna Matching Network
Value
Manufacturer
Part Number
ANT1
-
Amotech
AMAN301512ST01
L2
3.9 nH
Murata
LQP03TN3N9B02D
L9
1.8 nH
Murata
LQP03TN1N8C02D
C20
Not Populated
-
-
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6.2 EMC Regulations for 2.4 GHz
6.2.1 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.
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6.2.2 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 emmissions 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 for those the
-41.2 dBm limit should be applied. For the 4th harmonic the -20 dBc limit should be applied.
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6.2.3 Applied Emission Limits
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The FCC restricted band limits are radiated limits only. Besides that, Silicon Labs applies those to the conducted spectrum i.e. it is assumed that in case of a custom board an antenna is used which has 0 dB gain at the fundamental and the harmonic frequencies. In that
theoretical case, based on the conducted measurement, the compliance with the radiated limits can be estimated.
The overall applied limits are shown in the table below.
Frequency
2nd
4800~4967 MHz
3rd
7200~7450.5 MHz
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Table 6.3. Applied Limits for Spurious Emissions
4th
-41.2 dBm
-41.2 dBm
9600~9934 MHz
-30 dBm
12000~12417.5 MHz
-41.2 dBm
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5th
Limit
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6.3 Radiated Power Measurements
The output power of the EFR32 was set to 10 dBm. The board was supplied through its USB connector by connecting to a PC through
a USB cable.
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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.
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6.3.1 Maximum Radiated Power Measurement
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Figure 6.3. DUT Reference Planes
The measured maximums of the fundamental and the harmonics are shown in the table below.
Table 6.4. Maximums of the Measured Radiated Powers of BRD4160A
2.405 GHz
Fundamental
2nd harmonic
4th harmonic
Margin [dB]
Limit in EIRP [dBm]
9.1
XY/H
20.9
30
-55.4
XZ/H
14.2
-41.2
10
-41.2
20
-30
10
-41.2
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5th harmonic
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3rd harmonic
EIRP [dBm]
* Signal level is below the Spectrum Analyzer noise floor.
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As it can be observed the levels of the harmonics are far below the applied limit.
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Radio
6.3.2 Antenna Pattern Measurement
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The measured typical antenna patterns are shown in the figures below.
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Figure 6.4. Antenna Pattern - XY
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Figure 6.5. Antenna Pattern - XZ
Figure 6.6. Antenna Pattern - YZ
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6.4 EMC Compliance Recommendations
6.4.1 Recommendations for 2.4 GHz ETSI EN 300-328 Compliance
As it was shown in the previous chapter with the EFR32 output power set to 10 dBm the radiated power of the fundamental of the
BRD4160A complies with the 20 dBm limit of the ETSI EN 300-328. The harmonic emissions are under the -30 dBm limit with large
margin.
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6.4.2 Recommendations for 2.4 GHz FCC 15.247 Compliance
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As it was shown in the previous chapter with the EFR32 output power set to 10 dBm the radiated power of the fundamental of the
BRD4160A 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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Schematics, Assembly Drawings and BOM
7. Schematics, Assembly Drawings and BOM
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The schematics, assembly drawings and bill of materials (BOM) for the hardware included on the Thunderboard Sense are available
through Simplicity Studio when the kit documentation package has been installed.
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Kit Revision History and Errata
8. Kit Revision History and Errata
8.1 Revision History
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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 8.1 Kit Revision History on page 38
Thunderboard Sense
SLTB001A
25-08-16
1632000360
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B01
Figure 8.1. Revision Info
Table 8.1. Kit Revision History
Released
Description
C00
2017-09-28
Removed coin cell battery due to shipping restrictions.
B02
2017-04-05
Updated to BRD4160A Rev. B02.
B01
2016-08-25
Updated to BRD4160A Rev. B01.
B00
2016-08-23
Updated to BRD4160A Rev. B00.
A00
2016-06-22
Initial kit release with BRD4160A Rev A02.
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Kit Revision
8.2 Errata
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There are no known errata at present.
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Board Revision History and Errata
9. Board Revision History and Errata
9.1 Revision History
The board revision can be found laser printed on the board, and the board revision history is summarised in
Revision
Label Outline
B02
BRD4160A
Released
Description
2016-11-17
Minor update to PCB.
2016-08-25
Minor update to PCB.
2016-08-18
Removed engineering sample of Si7210 Hall-effect sensor.
2016-07-04
Initial release.
Rev. B02
162701381
B01
Rev. B01
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BRD4160A
Rev.
162701381
B00
BRD4160A
Rev. A02
A02
162701381
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BRD4160A
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162701381
B00
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Table 9.1. Board Revision History
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There are no known errata at present.
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Document Revision History
10. Document Revision History
Revision 1.1
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2017-10-10
• Removed CR2032 battery from Section 1.1 Kit Contents
• Updated section 8.1 and section 9.1.
Revision 1.01
2016-09-26
• Minor edit.
• Corrected release dates in table 8.1.
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Revision 1.00
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2016-09-20
• Initial document release.
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Rev. 1.1 | 40
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One-click access to MCU and
wireless tools, documentation,
software, source code libraries &
more. Available for Windows,
Mac and Linux!
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IoT Portfolio
www.silabs.com/IoT
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Simplicity Studio
SW/HW
www.silabs.com/simplicity
Quality
www.silabs.com/quality
Support and Community
community.silabs.com
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Disclaimer
Silicon Labs intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers using or
intending to use the Silicon Labs products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific device, and "Typical"
parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Labs reserves the right to make changes
without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy or completeness of the included
information. Silicon Labs shall have no liability for the consequences of use of the information supplied herein. This document does not imply or express copyright licenses granted
hereunder to design or fabricate any integrated circuits. The products are not designed or authorized to be used within any Life Support System without the specific written consent of
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