Silicon Laboratories BRD4257A, EFR32FG14, BRD4257B Reference Manual
EFR32FG14 2400/915 MHz Dual Band
19 dBm Radio Board
BRD4257A Reference Manual
The BRD4257A Flex
wireless applications. The board contains a dual-band Flex Gecko Wireless System-onChip and it is optimized for operating at 19 dBm output power. For the 2.4 GHz band
with the on-board printed antenna and UFL connector, radiated and conducted testing is
supported. For the 915 MHz band, the on-board SMA connector enables conducted
testing and attachment of external whip antenna for radiated tests.
The BRD4257A Flex Gecko Radio Board plugs into the Wireless Starter Kit Mainboard,
which is included with the Flex Gecko Starter Kit and gives access to display, buttons
and additional features from Expansion Boards. With the supporting Simplicity Studio
suite of tools, developers can take advantage of graphical wireless application development and visual energy profiling and optimization. The board also serves as an RF reference design for applications targeting 2.4 GHz and 915 MHz dual band wireless operation with 19 dBm output power.
This document contains a brief introduction and description of the BRD4257A Radio
Board features, focusing on the RF sections and performance.
Gecko Radio Board enables developers to develop proprietary
RADIO BOARD FEATURES
• Wireless SoC:
EFR32FG14P233F256GM48
•
CPU core: ARM
• Flash memory: 256 kB
• RAM: 32 kB
• Operation frequency: 2.4 GHz + 915 MHz
• Transmit power: 19 dBm
• 2.4 GHz: Integrated PCB antenna, UFL
connector (optional)
• 915 MHz: Single SMA connector both for
transmit and receive
• Crystals for LFXO and HFXO: 32.768 kHz
and 38.4 MHz
• 8 Mbit low-power serial flash for over-theair updates
Cortex®-M4 with FPU
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Table of Contents
1. Introduction ................................
4
2. Radio Board Connector ...........................5
2.1 Introduction...............................5
2.2 Radio Board Connector Pin Associations.....................5
3. Radio Board Block Summary .........................6
3.1 Introduction...............................6
3.2 Radio Board Block Diagram .........................6
3.3 Radio Board Block Description ........................6
3.3.1 Wireless MCU............................6
3.3.2 LF Crystal Oscillator (LFXO) .......................6
3.3.3 HF Crystal Oscillator (HFXO).......................6
3.3.4 Matching Network for Sub-GHz ......................6
3.3.5 Matching Network for 2.4 GHz ......................7
3.3.6 SMA Connector ...........................7
3.3.7 UFL Connector ...........................7
3.3.8 Radio Board Connectors ........................7
3.3.9 Inverted-F Antenna ..........................7
3.3.10 Serial Flash ............................7
3.3.11 Serial EEPROM ...........................7
4. RF Section ................................8
4.1 Introduction...............................8
4.2 Schematic of the RF Matching Network .....................8
4.2.1 Description of the Sub-GHz RF Matching ..................8
4.2.2 Description of the 2.4 GHz RF Matching ...................8
4.3 RF Section Power Supply ..........................8
4.4 Bill of Materials for the sub-GHz Matching ....................8
4.5 Bill of Materials for the 2.4 GHz Matching ....................9
4.6 Inverted-F Antenna ............................9
5. Mechanical Details .............................11
6. EMC Compliance ............................. 12
6.1 Introduction...............................12
6.2 EMC Regulations for 915 MHz ........................12
6.2.1 FCC15.247 Emission Limits for the 902-928 MHz Band ..............12
6.3 ETSI EN 300-328 Emission Limits for the 2400-2483.5 MHz Band ............12
6.4 FCC15.247 Emission Limits for the 2400-2483.5 MHz Band ..............12
6.5 Applied Emission Limits for the 2.4 GHz Band ...................12
7. RF Performance ............................. 13
7.1 Conducted Power Measurements .......................13
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7.1.1 Conducted Measurements in the 915 MHz Band ................13
7.1.2 Conducted Measurements in the 2.4 GHz Band ................14
7.2 Radiated Power Measurements ........................15
7.2.1 Radiated Measurements in the 915 MHz Band .................16
7.2.2 Radiated Measurements in the 2.4 GHz Band .................16
8. EMC Compliance Recommendations ..................... 17
8.1 Recommendations for 915 MHz FCC 15.247 Compliance ...............17
8.2 Recommendations for 2.4 GHz ETSI EN 300-328 Compliance .............17
8.3 Recommendations for 2.4 GHz FCC 15.247 Compliance ...............17
9. Board Revision History .......................... 18
10. Errata................................. 19
11. Document Revision History ........................ 20
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BRD4257A Reference Manual
Introduction
1. Introduction
The EFR32 Flex Gecko Radio Boards provide a development platform (together with the Wireless Starter Kit Mainboard) for the Silicon
Labs EFR32 Flex Gecko Wireless System-on-Chips and serve as reference designs for the matching networks of the RF interfaces.
The BRD4257A Radio Board supports dual-band operation with its integrated sub-GHz ISM band and 2.4 GHz band transceivers. The
sub-GHz section is designed to operate in the US FCC 902-928 MHz band with an external whip antenna, the 2.4 GHz section is designed to operate at the 2400-2483.5 MHz band with the on-board printed antenna. The matching networks are optimized for operating
at 19 dBm output power.
To develop and/or evaluate the EFR32 Flex Gecko, the BRD4257A Radio Board can be connected to the Wireless Starter Kit Mainboard to get access to display, buttons and additional features from Expansion Boards and also to evaluate the performance of the RF
interfaces.
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GND
F9 / PA3 / VCOM.#RTS_#CS
3v3
NC / P36
P200
Upper Row
NC / P38
NC / P40
NC / P42
NC / P44
DEBUG.TMS_SWDIO / PF1 / F0
DISP_ENABLE / SENSOR_ENABLE / PD15 / F14
UIF_BUTTON0 / PF6 / F12
UIF_LED0 / PF4 / F10
VCOM.#CTS_SCLK / PA2 / F8
UIF_BUTTON0 / PF6 / P4
DEBUG.TDO_SWO / PF2 / F2
DISP_SI / PC6 / F16
VCOM.TX_MOSI / PA0 / F6
PTI.DATA / PB12 / F20
DISP_EXTCOMIN / PD13 / F18
USB_VBUS
5V
Board ID SCL
GND
Board ID SDA
USB_VREG
F7 / PA1 / VCOM.RX_MISO
F5 / PA5 / VCOM_ENABLE
F3 / PF3 / DEBUG.TDI
F1 / PF0 / DEBUG.TCK_SWCLK
P45 / NC
P43 / NC
P41 / NC
P39 / NC
P37 / PD15 / DISP_ENABLE / SENSOR_ENABLE
F11 / PF5 / UIF_LED1
F13 / PF7 / UIF_BUTTON1
F15 / PC8 / DISP_SCLK
F17 / PD14 / DISP_SCS
F19 / PB13 / PTI.SYNC
F21 / PB11 / PTI.CLK
GND
VMCU_IN
VCOM.#CTS_SCLK / PA2 / P0
P201
Lower Row
VCOM.#RTS_#CS / PA3 / P2
UIF_BUTTON0 / PF6 / P4
UIF_BUTTON1 / PF7 / P6
GND
VRF_IN
P35 / PD15 / DISP_ENABLE / SENSOR_ENABLE
P7 / PC9
P5 / PC8 / DISP_SCLK
P3 / PC7
P1 / PC6 / DISP_SI
P33 / PD14 / DISP_SCS
P31 / PD13 / DISP_EXTCOMIN
P29 / NC
P27 / NC
P25 / NC
P23 / NC
P21 / NC
P19 / NC
P17 / NC
P15 / NC
P13 / PC11
P11 / PA1 / VCOM.RX_MISO
P9 / PA0 / VCOM.TX_MOSI
NC / P34
UIF_LED1 / PF5 / P32
NC / P30
DEBUG.TDO_SWO / PF2 / P28
DEBUG.TMS_SWDIO / PF1 / P26
DEBUG.TCK_SWCLK / PF0 / P24
PTI.SYNC / PB13 / P22
PTI.DATA / PB12 / P20
PTI.CLK / PB11 / P18
VCOM_ENABLE / PA5 / P16
PA4 / P14
PC10 / P12
DEBUG.TDI / PF3 / P10
UIF_LED0 / PF4 / P8
BRD4257A Reference Manual
Radio Board Connector
2. Radio Board Connector
2.1 Introduction
The board-to-board connector scheme allows access to all EFR32FG14 GPIO pins as well as the RESETn signal. For more information
on the functions of the available pins, see the EFR32FG14 data sheet.
2.2 Radio Board Connector Pin Associations
The figure below shows the mapping between the connector and the EFR32FG14 pins and their function on the Wireless Starter Kit
Mainboard.
Figure 2.1. BRD4257A Radio Board Connector Pin Mapping
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3. Radio Board Block Summary
EFR32
Inverted-F
PCB
Antenna
2.4 GHz RF
UFL
Connector
LF
Crystal
32.768k
HF
Crystal
38.4M
Radio
Board
Connectors
8 Mbit
MX25R
Serial Flash
I2C
24AA024
Serial EEPROM
Matching
Network &
Output
Selection
GPIO
UART
Debug
Packet Trace
AEM
I2C
SPI
SPI
2.4 GHz RF
2.4 GHz RF
SubGHz RF
Matching
Network &
DC Bias
SubGHz RF
SMA
Connector
EFR32
EFR32
Wireless SoC
3.1 Introduction
This section gives a short introduction to the blocks of the BRD4257A Radio Board.
3.2 Radio Board Block Diagram
The block diagram of the BRD4257A Radio Board is shown in the figure below.
BRD4257A Reference Manual
Radio Board Block Summary
Figure 3.1. BRD4257A Block Diagram
3.3 Radio Board Block Description
3.3.1 Wireless MCU
BRD4257A Flex Gecko Radio Board incorporates an EFR32FG14P233F256GM48 Wireless System-on-Chip featuring 32-bit Cor-
The
tex®-M4 with FPU core, 256 kB of flash memory, 32 kB of RAM, an integrated 2.4 GHz band and an integrated sub-GHz ISM band
transceiver with output power up to 19 dBm. For additional information on the EFR32FG14P233F256GM48, refer to the EFR32FG14
Data Sheet.
3.3.2 LF Crystal Oscillator (LFXO)
The BRD4257A Radio Board has a 32.768 kHz crystal mounted. For details regarding the crystal configuration, refer to Application
Note "AN0016: Oscillator Design Considerations".
3.3.3 HF Crystal Oscillator (HFXO)
The BRD4257A Radio Board has a 38.4 MHz crystal mounted. For details regarding the crystal configuration, refer to Application Note
"AN0016: Oscillator Design Considerations".
3.3.4 Matching Network for Sub-GHz
The BRD4257A Radio Board incorporates a sub-GHz matching network which connects both the sub-GHz TX and RX pins of the
EFR32FG14 to the SMA connector to be able to transmit and receive with one antenna. The component values have been optimized
for the 915 MHz band RF performance and current consumption with 19 dBm output power.
For a detailed description of the matching network see Chapter 4.2.1 Description of the Sub-GHz RF Matching.
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3.3.5 Matching Network for 2.4 GHz
BRD4257A Reference Manual
Radio Board Block Summary
The BRD4257A
Radio Board incorporates a 2.4 GHz matching network which connects the 2.4 GHz TRX pin of the EFR32FG14 to the
one on-board printed inverted-F antenna. The component values have been optimized for the 2.4 GHz band RF performance and current consumption with 19 dBm output power.
For a detailed description of the matching network, see Chapter 4.2.2 Description of the 2.4 GHz RF Matching.
3.3.6 SMA Connector
To be able to perform conducted measurements or mount external antenna for radiated measurements, range tests etc., Silicon Labs
added an SMA connector to the Radio Board. The connector allows an external 50 Ohm cable or antenna to be connected during design verification or testing.
3.3.7 UFL Connector
To be able to perform conducted measurements, Silicon Labs added a UFL connector to the Radio Board. The connector allows an
external 50 Ohm cable or antenna to be connected during design verification or testing.
Note: By default, the output of the matching network is connected to the printed inverted-F antenna by a series component. It can be
connected to the UFL connector as well through a series 0 Ohm resistor, which is not mounted by default. For conducted measurements through the UFL connector, the series component to the antenna should be removed and the 0 Ohm resistor should be mounted
(see Chapter 4.2.2 Description of the 2.4 GHz RF Matching for further details).
3.3.8 Radio Board Connectors
Two dual-row, 0.05” pitch polarized connectors make up the BRD4257A Radio Board interface to the Wireless Starter Kit Mainboard.
For more information on the pin mapping between the EFR32FG14P233F256GM48 and the Radio Board Connector, refer to Chapter
2.2 Radio Board Connector Pin Associations.
3.3.9 Inverted-F Antenna
The BRD4257A Radio Board includes a printed inverted-F antenna (IFA) tuned to have close to 50 Ohm impedance at the 2.4 GHz
band.
For detailed description of the antenna, see Chapter 4.6 Inverted-F Antenna.
3.3.10 Serial Flash
The BRD4257A Radio Board is equipped with an 8 Mbit Macronix MX25R SPI flash that is connected directly to the EFR32FG14 to
support over-the-air (OTA) updates. For additional information on the pin mapping see the schematic of the BRD4257A.
3.3.11 Serial EEPROM
The BRD4257A Radio Board is equipped with a serial I2C EEPROM for board identification and to store additional board related information.
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