ST X-NUCLEO-S2868A2 User manual

Introduction
The X-NUCLEO-S2868A2 expansion board is based on the S2-LP ultra-low power RF transceiver and operates in the 868 MHz
ISM frequency band.
The X-NUCLEO-S2868A2 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.
The expansion board is compatible with ST morpho and Arduino UNO R3 connectors.
Figure 1. X-NUCLEO-S2868A2 expansion board
Getting started with the X-NUCLEO-S2868A2 Sub-1 GHz 868 MHz RF expansion
board based on S2-LP radio for STM32 Nucleo
UM2638
User manual
UM2638 - Rev 1 - December 2019
For further information contact your local STMicroelectronics sales office. www.st.com

1Acronyms 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
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Acronyms and abbreviations
UM2638 - Rev 1 page 2/19

2Getting started
2.1 Overview
The X-NUCLEO-S2868A2 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
•BALF-SPI2-01D3 IPD balun for matching network and harmonics filter
• Sigfox compatible
• Sample firmware for P2P communication
• 6LoWPAN compatible thanks to STM32Cube
• RoHS and WEEE compliant
The X-NUCLEO-S2868A2 expansion board can be used for the evaluation of the S2-LP device in multiple
applications:
• wM-Bus applications
• Point-to-point communication protocol
• 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
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Getting started
UM2638 - Rev 1 page 3/19

2.2 Hardware and software requirements
To use the X-NUCLEO-S2868A2 expansion board with STM32 Nucleo development boards, connect the boards
as shown below.
Figure 2. X-NUCLEO-S2868A2 expansion board connected to an STM32 Nucleo development board
The interconnection between the STM32 Nucleo and the X-NUCLEO-S2868A2 is designed to allow the use of
any STM32 Nucleo board, although complete testing has only been performed on the NUCLEO-L053R8,
NUCLEO-F401RE and NUCLEO-L152RE boards hosting ultra-low power STM32 microcontrollers.
The minimum hardware and software requirements are listed below:
• 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 protocol.
2.3 Board setup
Step 1. Check that the jumper on JP1 connector is connected to provide the required voltage to the board
devices.
Step 2. Connect the X-NUCLEO-S2868A2 to the STM32 Nucleo board as shown in Figure 2.
Step 3. Power the STM32 Nucleo development board using the Mini-B USB cable.
Step 4. Program the firmware in the STM32 on the STM32 Nucleo development board using the firmware
sample provided.
Step 5. Preset the reset button on the STM32 Nucleo development board.
The evaluation kit is ready-to-use.
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Hardware and software requirements
UM2638 - Rev 1 page 4/19

3Hardware description and configuration
3.1 Interconnection details
The X-NUCLEO-S2868A2 expansion board and the NUCLEO-F401RE or NUCLEO-L152RE board connection
details are listed in the table below.
Table 2. X-NUCLEO-S2868A2 and NUCLEO-L152RE connection details (left connector)
Signal name
NC IOREF RESET 3V3 5VGND GND VIN A0 A1 A2 A3 A4 A5
Connector name
CN6 Power CN8 Analog
Pin number
12 3 45678123456
NUCLEO-L152RE MCU port
PA0 PA1 PA4 PB0 PC1 PC0
X-NUCLEO-S2868A2 expansion board signals
3V3 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-S2868A2 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-S2868A2 expansion board signals
GND SPI_C
LK(1)
SPI_MI
SO
SPI_M
OSI
SPI_C
SN(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 Nucleo 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
UM2638 - 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 PA0 PC1
To 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 R6, unmount R11
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-S2868A2 expansion board power consumption, use jumper JP1: connect an ammeter
probe between the connector pins 1 and 2 for measurements.
3.4 X-NUCLEO-S2868A2 component placement details
The figure below shows the component placement on the X-NUCLEO-S2868A2 expansion board.
Figure 3. X-NUCLEO-S2868A2 on-board device placement
1. Arduino UNO R3 connector
2. Arduino UNO R3 connector
3. S2-LP
4. EEPROM
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Current measurement
UM2638 - Rev 1 page 6/19

4X-NUCLEO-S2868A2 on-board device description
4.1 SPI EEPROM
The M95640-R is a 64 Kbit serial SPI bus EEPROM with high-speed clock interface. The device can be used to
store the configuration parameters related to S2-LP RF device application or settings.
Features Description
Order code M95640-RMC6TG
Package MLP8
Operating voltage 1.8 to 5.5 V
4.2 S2-LP RF transceiver
The X-NUCLEO-S2868A2 expansion board is based on the S2-LP standalone RF transceiver. It operates in the
868 MHz ISM frequency band and wireless M-Bus.
The S2-LP narrow band ultra-low power sub-1 GHz transceiver is tuned for 430-470 MHz and 860 - 940 MHz
frequency bands and programmable RF output power up to +16 dBm.
Table 5. S2-LP details
Features Description
Order code S2-LPQTR
Package QFN24 4x4x1
Operating voltage 1.8 to 3.6 V
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X-NUCLEO-S2868A2 on-board device description
UM2638 - Rev 1 page 7/19

5Schematic diagrams
Figure 4. X-NUCLEO-S2868A2 circuit schematic
LL__1100UU__00880055
RR__110000kk__004400
CSN
1100uuFF
TX
VDDANASYNTH
SDA
SSTTSSAAFFEE--AA110000
CC__115500nn__00440022
1100RR
CC11
GPIO1
LL1122
NNMM
C2
ANT B2
22
1100ppFF
7
SCL
NNMM
LL1111
1. 4 V t o 1. 8 V max
VRSYNTH
VDDSMPS
2
SDI
18
SDI 17
CC3322
nS
1
RR__110000kk__00440022
1RESET
LL33
GND
25
OUT
RR3366
CC__115500nn__00440022
CC3344
CCRRYYSSTTAALL__NNXX11661122SSAA
CC__44..77UU__00660033
VDDVCOTX
+3V3
SDO
C1
RX_N
GPIO0
CC__110000pp__00440022
CC22
10 VDDVCOTX
TX
VDD
SS22--LLPP
SDO
1
VDD
GPIO1 21
NC 8
RX_P
A1
CC__11uu__00660033
AAMM1111DDGG--SSTT0011
7
CC__110000pp__00440022
VDDSMPS
RR3377
00RR
110000ppFF
VSMPS2
11
VRRF
12
CC55
CC4422
CC2222
GPIO3
B1
RR3355
IN
LL__1122nnHH__00660033
4GND
NC
3
CC1100
CC1122
VRSYNTH
RR3388
VCC
2
19
GPIO0 20
D5
NM
OUT
IN
JJ11
NNMM
CC1177
SDN
GPIO2
CC99
A2
4
CC__115500nn__00440022
22..22KK
3
CC1188
RR__110000kk__00440022
UU44
CC3366
VDDRXDIG
GPIO2
22..22KK
CC__115500nn__00440022
RR33
CC__110000pp__00440022
RR22
CC__110000pp__00440022
CC1166
NM
nW
3
110000ppFF
RXN 13
RR11
UU22
22..77ppFF,,00440022
CC__1122ppFF__00660033
UU33
SMPS1
3
VDDANASYNTH
8
2
VCC 8
YY11
CC3300
110000nnFF
CC1133
NC 6
4VSS
CSN
14
15
SSMMAA AANNTTEENNNNAA
MM9955664400
7
CC2255
+3V3
+3V3
CC44 CC88
44..77nnHH
RXP
SDN
6
CC__115500nn__00440022
SCLK
VSMPS2
nS
VRSYNTH
9
VDD
1
LL88
CC__110000nn__00440022
CC__447700pp__00440022
SCL
SCLK
+3V3
VDDRXDIG
SDO
Q
2
+3V3
22..22KK
nHOLD
C6
CC4411
VDDRXDIG
SDA
VDDVCOTX
CC__115500nn__00440022
GND1
XOUT
5XIN
NNMM
LL1133
CC3355
VREFVCO
EE11
LL77
CC__115500nn__00440022
RR2244
LL__3399nnHH__00440022
SDI
CC66
5
16
SCLK
UU11
VDDANASYNTH
VDD
VDDSMPS
SMPS2
4
LL22
GND2
GPIO3 23
VRDIG 24
CC1144
BBAALLFF--SSPPII22--0011DD33
Figure 5. X-NUCLEO-S2868A2 circuit schematic - Arduino connectors
RR1100
RR1111
SDA
4
3V3
GPIO3
SDN
+5V
D8
and Female on
CCNN55
RR1166
A0 1
D4
5
10
D6
7
1
GPIO0
SCL
5V 5
00
RR1155
nS
00
1
SCL
TXD/D1
PWM/D9
3
1
JJPP11
PA3RR2233
NNMM
6
GND
A3 4
CSN
Top
8 Pass-Through:
Male on Bottom
00
AREF
9SDA
RR1133
PWM/D10
4
RXD/D0
2
00
PA2
RR55
D7
8
PC7
nS
RR66
RR1122
A4 5
RR44
SDI
8
+3V3
LLEEDD
SCLK
RR1188 NNMM
SDO
GPIO0
PC7
RESET
NNMM
CCNN88
6 Pass-Through:
Male on Bottom
Top
and Female on
Pass-Through:
Male on Bottom
Top
and Female on
Pass-Through:
Male on Bottom
Top
and Female on
NC 1
A5 6
CCNN66
7
GND
D3
4
VIN 8
NNMMRR1177
D5
6
MISO/D12
6
CSN
00
IOREF
RR99
RR2222
VDD
MOSI/PWM/D11
5
NNMM
2
00
RESET
2
GPIO1
RR1144 00
SCK/D13
7GND
NNMMRR1199
00
SDN
A2 3
RR77
CCNN99
SCLK
VIN
JJUUMMPPEERR
D2
3
32
333300 DD11
GPIO2
AVDDIOREF
00
A1 2
00
Arduino UNO R3 SX connector Arduino UNO R3 DX connector
UM2638
Schematic diagrams
UM2638 - Rev 1 page 8/19

Figure 6. X-NUCLEO-S2868A2 circuit schematic - ST morpho connectors
13
15
RESET
+3V3
25
27
ST morpho DX connector
Pass-Through: Female on
Bottom and Male on Top Pass-Through: Female on Bottom and Male on Top
PC9
BOOT0
22
PD8
11
13
36
38
IOREF
17
19
PA13 PA6
PA7
AGND
PC10
PA15
31
24
26
PC2
PC3
37
11
2
4
6
8
10
21
E5V
PA14
PB0
PC1
26
28
PB15
PC12
PB10
2 30 27 29
PB13
12
14
CN7
PC0
PC5
PC15
PA3
PB14
PA8
33
PA10
PH1/PF1/PD1
PA12
35
1
3
5
7
9
34
NC/PF7
32
PC11
PD2
1
3
5
7
9
PH0/PF0/PD0
PA2
PA4
PA9
2
4
6
8
10
PC14
16
PA11
30
32
35
34
PB4
PB1
9
18
PC7
12
14
PC6
PB12
23
PA5
33
36
38
28
19
PB5
17
1
20
PB8
PC13
U5V
VIN
PB6
16
PC4
NC/PF6
PB2
NC/PF4
25
18
PB9
AVDD
3
37
CN10
21
23 22 24
PB3
PB7
15
PA0
PA1
+5V
NC/PF5
PC8
VLCD/VBAT
PB11/NC
VDD
20
ST morpho SX connector
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Schematic diagrams
UM2638 - Rev 1 page 9/19

6Bill of materials
Table 6. X-NUCLEO-S2868A2 bill of materials
Item Q.ty Ref. Part/Value Description Manufacturer Order code
1 1 CN5
CON10 550
VAC 2.54 mm
pitch
Connector 4UCON SSQ-110-03-F-S
2 2 CN6, CN9 CON8 550 VAC
2.54 mm pitch Connectors 4UCON SSQ-108-03-F-S
3 2 CN7, CN10
Header 19x2
not assembled
2.54 mm pitch
Connectors 4UCON SSQ-106-03-F-S
4 1 CN8 CON6 550 VAC Connector
5 1 C1
4.7 µF 16 V
±10%
SMD-0603
VBAT filter
capacitors Murata CC0603KRX5R7BB475
6 7
C2, C5, C10,
C22, C30, C32,
C34
150 nF 16 V
±10%
SMD-0402
Filter capacitors Murata CL05B154KO5NNNC
74C4, C6, C8,
C35
100 pF 16 V
±10%
SMD-0402
VBAT bypass
capacitors Murata C0402C101J3GACTU
8 1 C9
100 nF 16 V
±10%
SMD-0402
Decoupling
capacitor Murata GRM155R71C104KA88D
9 1 C12 1 µF 16 V ±10%
SMD-0603
SMPS OUT filter
capacitor Murata EMK107BJ105KA-T
10 1 C13 10 pF 50 VDC
±5% SMD-0402 Capacitor KEMET C0402C100J5GACAUTO7411 or
equivalent
11 1 C14 12 pF 50 V ±5%
SMD-0402 Capacitor Yageo CC0402JRNPO9BN120 or equivalent
12 2 C16, C36 100 pF 16V
±5% SMD-0402 KEMET C0402C101J3GACTU
13 1 C17 100 pF 16V
±5% SMD-0402 not mounted KEMET C0402C101J3GACTU
14 1 C25
470 pF 16V
±10%
SMD-0402
VREFVCO filter Murata UMK105B7471KV
15 1 C41 100 nF 50 VDC
±5% SMD-0402 Capacitor Murata GRM155R61H104JE14D or
equivalent
16 1 C42
10 µF 16 V
±10%
SMD-0805
Capacitor YAGEO CL21A106KOQNNNG
17 1 D1 LED 20 mA
SMD-0603 Red LED OSRAM LS Q976-NR-1
18 1 E1 AM11DG-ST01 SMD antenna (not
mounted) Mitsubishi AM11DG-ST01B
19 1 JP1 VH/T M2OE/
W.325/10/ MOD Jumper Any Any
20 1 J1 RF_IN/OUT,
jack assembly SMA antenna Emerson 142-0701-881
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Bill of materials
UM2638 - Rev 1 page 10/19