Introduction
The X-NUCLEO-S2868A1 expansion board is based on the S2-LP radio and operates in the 868 MHz ISM frequency band.
The expansion board is compatible with ST morpho and Arduino UNO R3 connectors.
The X-NUCLEO-S2868A1 interfaces with the STM32 Nucleo microcontroller via SPI connections and GPIO pins. You can
change some of the GPIOs by mounting or removing the resistors.
Figure 1. X-NUCLEO-S2868A1 expansion board
Getting started with the X-NUCLEO-S2868A1 Sub-1 GHz 868 MHz RF expansion
board based on S2-LP radio for STM32 Nucleo
UM2405
User manual
UM2405 - Rev 1 - May 2018
For further information contact your local STMicroelectronics sales office.
www.st.com
1 Acronyms and abbreviations
Table 1. List of acronyms
Acronym Description
AMR Automatic meter reading
EEPROM Electrically erasable programmable read only memory
GHz Giga Hertz
GUI Graphical user interface
LED Light emitting diode
MCU Microcontroller unit
P2P Point-to-point communication
RF Radio frequency communication
SPI Serial peripheral interface
USB Universal serial bus
wM-Bus Wireless metering bus
WSN Wireless sensors network
UM2405
Acronyms and abbreviations
UM2405 - Rev 1
page 2/19
2 Getting started
2.1 Overview
The X-NUCLEO-S2868A1 main features are:
•
Based on S2-LP
radio
•
S2-LP narrow band ultra-low power sub-1 GHz transceiver tuned for 860 - 940 MHz frequency band
• Programmable RF output power up to +16 dBm
• Modulation schemes: 2-FSK, 2-GFSK, 4-FSK, 4-GFSK, OOK and ASK
• Air data rate from 0.1 to 500 kbps
• Ultra-low power consumption: 7 mA RX and 10 mA TX at +10 dBm
• IEEE 802.15.4g hardware packet support with whitening, FEC, CRC and dual SYNC word detection
• RX and TX 128 byte FIFO buffers
• Support to wireless M-Bus
• Excellent performance of receiver sensitivity (up to -130 dBm)
• Automatic acknowledgement, retransmission and timeout protocol engine
• Compatible with STM32 Nucleo boards
• Compatible with Arduino UNO R3 connectors
• Support to SMD and SMA antennas
• BALF-SPI2-01D3 IPD balun for matching network and harmonics filter
• Sigfox compatible
• Sample firmware for P2P communication
• 6LoWPAN compatible thanks to STM32Cube
• RoHS compliant
The X-NUCLEO-S2868A1 expansion board can be used for the evaluation of the S2-LP device in multiple
applications.
The following demo samples are available for testing:
• wM-Bus demo
• Point-to-point communication protocol demo
• 6LoWPAN applications
• SigFox communication
You can develop other applications for evaluating the devices, such as:
• SigFox communication
• Automatic meter reading
• Home and building automation
• WSN
• Industrial monitoring and control
• Wireless fire and security alarm systems
2.2 Hardware and software requirements
To use STM32 Nucleo development boards with the X-NUCLEO-S2868A1
expansion board, connect the boards
as shown below.
UM2405
Getting started
UM2405 - Rev 1
page 3/19
Figure 2. X-NUCLEO-S2868A1 expansion board connected to an STM32 Nucleo development board
The interconnection between the STM32 Nucleo and the X-NUCLEO-S2868A1 has been designed to allow using
any STM32 Nucleo board, although complete testing has been performed using NUCLEO-L053R8, NUCLEO-
F401RE and NUCLEO-L152RE boards hosting the ultra-low power STM32.
The following software and hardware specifications are required:
• a PC/laptop with Microsoft Windows (7 and above) to install the software package (X-CUBE-SUBG1)
• a type A USB to mini-B USB cable to connect the STM32 Nucleo board to the PC/laptop
• 128 MB of RAM
• Approximately 40 MB of hard disk space for the firmware
• Approximately 15 MB of hard disk space for the wM-Bus GUI
The use of the wM-Bus concentrator with the GUI requires additional boards to be connected to the PC. The GUI
can be used to check the wM-Bus communication sample.
2.3 Board setup
Step 1. Check that the jumper on J1 connector is connected to provide the required voltage to the board
devices.
Step 2. Connect the X-NUCLEO-S2868A1 to the STM32 Nucleo
board as shown in Figure 2. X-NUCLEO-
S2868A1 expansion board connected to an STM32 Nucleo development board
Step 3. Power the Nucleo development board using the Mini-B USB cable
Step 4. Program the firmware in the STM32 on the Nucleo development board using the firmware sample
provided
Step 5. Reset the MCU board using the reset button on the Nucleo development board
Step 6. The evaluation kit is ready-to-use
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Board setup
UM2405 - Rev 1
page 4/19
3 Hardware description and configuration
3.1 Interconnection details
The X-NUCLEO-S2868A1 expansion board and the NUCLEO-F401RE or NUCLEO-L152RE board connection
details are listed in the table below
.
T
able 2. X-NUCLEO-S2868A1 and NUCLEO-L152RE connection details (left connector)
Signal name
NC IOREF
RESET
3
V
3
5
V
GND GND VIN A0 A1 A2 A3 A4 A5
Connector name
CN6 Power CN8 Analog
Pin number
1 2 3 4 5 6 7 8 1 2 3 4 5 6
NUCLEO-L152RE MCU port
PA0 PA1 PA4 PB0 PC1 PC0
X-NUCLEO-S2868A1 expansion board signals
3
V
3
GND GND GPIO0 CSN GPIO1 GPIO2
GPIO0
(1)
GPIO3
1. Used to enable different configurations in case a signal conflict occurs when using other expansion board (refer to next
section).
Table 3. X-NUCLEO-S2868A1 and NUCLEO-L152RE connection details (right connector)
Signal name
D15 D14
AREF
GND D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Connector name
CN5 Digital CN9 Digital
Pin number
10 9 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
NUCLEO-L152RE MCU port
PB8 PB9 PA5 PA6 PA7 PB6 PC7 PA9 PA8
PB10
PB4 PB5 PB3
PA10
PA2 PA3
X-NUCLEO-S2868A1 expansion board signals
GND
SPI_
CLK
(
1)
SPI_
MIS
O
SPI_
MOS
I
SPI_
CSN
(
1)
nS
(1)
SDN
SDN
(
1)
nS
SPI_
CLK
1. Optional connection
3.2 SPI and GPIO connection options
The SPI and GPIO connection options between the STM32 and S2-LP can be used to enable different
configurations in case a signal conflict occurs when using other expansion boards.
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Hardware description and configuration
UM2405 - Rev 1
page 5/19
Table 4. S2-LP interface (optional) with STM32 Nucleo board
S2-LP signal Default STM32 port Optional STM32 port
GPIO0 PC7
PC1
T
o use the optional connection, mount R18, unmount R12
CSn PA1
PB6
To use the optional connection, mount R9, unmount R13
CLK PB3
PA5
To use the optional connection, mount R8, unmount R6
nS PB4
PA9
To use the optional connection, mount R7, unmount R22
SDN PA8
PB10
To use the optional connection, mount R19, unmount R10
To use the optional connections, modify the firmware on the basis of the STM32 resources used.
3.3 Current measurement
To monitor the X-NUCLEO-S2868A1 expansion board power consumption, use jumper J1: connect an ammeter
probe between the connector pins 1 and 2 for measurements.
3.4 X-NUCLEO-S2868A1 component placement details
The figure below shows the component placement on the X-NUCLEO-S2868A1 expansion board.
UM2405 Current
measurement
UM2405 - Rev 1
page 6/19
Figure 3. X-NUCLEO-S2868A1 on-board device placement
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