ST X-NUCLEO-S2915A1 User manual

Introduction
The X-NUCLEO-S2915A1 expansion board is based on the S2-LP radio and operates in the 915 MHz ISM frequency band.
The expansion board is compatible with ST morpho and Arduino UNO R3 connectors.
The X-NUCLEO-S2915A1 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-S2915A1 expansion board
Getting started with the X-NUCLEO-S2915A1 Sub-1 GHz 915 MHz RF expansion
board based on S2-LP radio for STM32 Nucleo
UM2641
User manual
UM2641 - Rev 1 - November 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
UM2641 - Rev 1 page 2/20

2Getting started
2.1 Overview
The X-NUCLEO-S2915A1 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 +27 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
• Sigfox compatible
• Sample firmware for P2P communication
• 6LoWPAN compatible thanks to STM32Cube
• FCC ID: S9NS2915A
• IC ID: 8976C-S2915A1
• RoHS and WEEE compliant
2.2 Typical applications
The X-NUCLEO-S2915A1 expansion board can be used for the evaluation of the S2-LP device in multiple
applications:
•wM-Bus application
• Point-to-point communication protocol
• 6LoWPAN applications
• SigFox communication
You can develop other applications for evaluating the devices, such as:
• Automatic meter reading
• Home and building automation
• WSN
• Industrial monitoring and control
• Wireless fire and security alarm systems
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Getting started
UM2641 - Rev 1 page 3/20

2.3 Hardware and software requirements
To use STM32 Nucleo development boards with the X-NUCLEO-S2915A1 expansion board, connect the boards
as shown below.
Figure 2. X-NUCLEO-S2915A1 expansion board connected to an STM32 Nucleo development board
The interconnection between the STM32 Nucleo and the X-NUCLEO-S2915A1 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 protocol.
2.4 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-S2915A1 to the STM32 Nucleo 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.
The evaluation kit is ready-to-use.
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Hardware and software requirements
UM2641 - Rev 1 page 4/20

3Hardware description and configuration
3.1 Interconnection details
The X-NUCLEO-S2915A1 expansion board and the NUCLEO-F401RE or NUCLEO-L152RE board connection
details are listed in the table below.
Table 2. X-NUCLEO-S2915A1 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
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-S2915A1 expansion board signals
3V3 GND GND GPIO0 CSN GPIO1 GPIO2 GPIO0(1) GPIO3
1. Optional connection.
Table 3. X-NUCLEO-S2915A1 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-S2915A1 expansion board signals
SCL SDA 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.
Table 4. S2-LP interface with STM32 Nucleo board
S2-LP signal Default STM32 port Optional STM32 port
CSn PA1 PB6
To use the optional connection, mount R9, unmount R13
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Hardware description and configuration
UM2641 - Rev 1 page 5/20

S2-LP signal Default STM32 port Optional STM32 port
CLK PB3 PA5
To use the optional connection, mount R6, unmount R11
nS PB4 PA9
To use the optional connection, mount R7, unmount R19
SDN PA8 PB10
To use the optional connection, mount R18, unmount R10
To use the optional connections, modify the firmware on the basis of the STM32 resources used.
Table 5. SKY66420 power amplifier settings
SKY66420 SW1 SW2
LNA ON (default) 100 pF capacitor between pin1 and pin2 (pin1 and
pin3 open)
100 pF capacitor between pin1 and pin3 (pin1 and
pin2 open)
LNA OFF 100 pF capacitor between pin1 and pin3 (pin1 and
pin2 open)
100 pF capacitor between pin1 and pin2 (pin1 and
pin3 open)
Table 6. SKY66420 interface with STM32 Nucleo board
SKY66420 signal Default STM32 port Optional STM32 port
GPIO0 PA0 PC1
To use optional connection mount R25, unmount R12
GPIO1 PA4 N.A.
GPIO2 PB0 N.A.
3.3 Current measurement
To monitor the X-NUCLEO-S2915A1 expansion board power consumption, use jumper J1: connect an ammeter
probe between the connector pins 1 and 2 for measurements.
3.4 X-NUCLEO-S2915A1 component placement details
The figure below shows the component placement on the X-NUCLEO-S2915A1 expansion board.
UM2641
Current measurement
UM2641 - Rev 1 page 6/20

Figure 3. X-NUCLEO-S2915A1 on-board device placement
1. Arduino UNO R3 left connector
2. Arduino UNO R3 right connector
3. S2-LP
4. SKY66420
12
3
4
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X-NUCLEO-S2915A1 component placement details
UM2641 - Rev 1 page 7/20

4X-NUCLEO-S2915A1 on-board device description
4.1 S2-LP radio
The X-NUCLEO-S2915A1 expansion board is based on the S2-LP standalone RF transceiver. It operates in the
915 MHz ISM frequency band and wireless M-Bus.
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 7. S2-LP details
Features Description
Order code S2-LPQTR
Package QFN24 4x4x1
Operating voltage 1.8 to 3.6 V
4.2 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
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X-NUCLEO-S2915A1 on-board device description
UM2641 - Rev 1 page 8/20

5Schematic diagrams
Figure 4. X-NUCLEO-S2915A1 circuit schematic
24
C32
C_220n_0402
15
VDDRXDIG
GND
4
C16
NP
R1
R_100k_0402
C50
C_1p5_0402
CSN
OUT
GPIO2
+3V3
22
C37 2p4F
GPIO0
VRRF
L10
L_5n6H_0402
L8
L_15nH_0402
C11
C_220n_0402
C34
C_3p3F_0402
SW1
1
9
2
NC
GND
NC
5
U4
SKY66420
7
L2
L_10U_0603
VCC0 15
SW2
NC
C30
C_220n_0402
C47
C_100p_0402
C23 1.5pF
VDDVCOTX
3
10
C48
C_1p2_0402
C37 2p4F
10
C8
C_100p_0402
2
C18
NM
C24
C_100p_0402
nS
C50
C_1p5_0402
8
C55 33pF
VDD
RX
R44
2.2K
C61
NP
C5
C_220n_0402
SDN
25
3
VDDSMPS
GND
U5
STSAFE-A100
18
L24 4n7H
L26
7n5H
C31
2p2F
R1
R_100k_0402
C9
C_100n_0402
L27 2n7H
C36
C_220n_0402
C17
100pF
R3
R_100k_0402
C56 1nF
C44
C_2p7F_0402
C9
C_100n_0402
SDA
L7
L_4n7H_0402
VDD
1. 4 V t o 1. 8 V max
C
C61
NP
7
6
7
ANT
13
4
SW2
9
L3
L_39nH_0402
CPS
5
TX_ALT
L13
L_18nH_0402
2
C46
C_100p_0402
C12
C_1u_0402
L9
L_6n8H_0402
1
C6
C_100p_0402
C38
NP
C51
C_100p_0402
GND
16
R3
R_100k_0402
14
SDA
R45 2.2K
C58 120pF
C41
C_100p_0402
C55 33pF
LNA ON: SW1 soldered a 100 pF cap between 1 - 2
SW2 soldered a 100 pF cap between 1 - 3
LNA OFF: SW1 soldered a 100 pF cap between 1 - 3
SW2 soldered a 100 pF cap between 1 - 2
C60
NP
R2
R_100k_040
GPIO3
C40
12pF
GPIO0
GPIO3
C10
C_220n_0402
C43
C_1p5F_0402
E1
AM11DG-ST01
L12
L_18nH_0402
VDDRXDIG
C1
C_4.7U_0402
nS
VDDANASYNTH
1
SMPS1
TX
U4
SKY66420
8
RX_FLT
C57
4u7F
8
R2
R_100k_040
C3
C_100p_0402
TX
NC
C52
100nF
L28
6n8H
TX
L14
4.7nH
U1
M95640
GND
C35
C_5p6F_0402
SDI
R45 2.2K
C25
C_470p_0402
C59 10nF
C54
10pF
Y1
CRYSTAL_NX1612SA
SDO
19
VCC
C1
C_4.7U_0402
C16
NP
C24
C_100p_0402
C32
C_220n_0402
C42
NP
C36
C_220n_0402
13
IN
RXN
VSS
VDDVCOTX
+3V3
L3
L_39nH_0402
C25
C_470p_0402
C59 10nF
C62
C_100p_0402
L14
4.7nH
C4
C_100p_0402
nHOLD
1
VRSYNTH
PA_OUT
XOUT
12
C57
4u7F
R20
R_10ohm_0402
4
VSMPS2
L24 4n7H
L11
L_27nH_0402
C6
C_100p_0402
RESET
C7
C_220nF_0402
C23 1.5pF
U1
M95640
C53
10uF/0805
16
SCLK
C33
NP
C42
NP
17
SDO
C13
C_100p_0402
C41
C_100p_0402
L26
7n5H
L9
L_6n8H_0402
GPIO1
C31
2p2F
L2
L_10U_0603
SDI
2
C35
C_5p6F_0402
GPIO1
L10
L_5n6H_0402
21
C10
C_220n_0402
C62
C_100p_0402
VRSYNTH
IN
VDDANASYNTH
1
8
R20
R_10ohm_0402
VCC
C11
C_220n_0402
C22
C_220n_0402
L25 4n7H
VRSYNTH
VDDSMPS
+3V3
C49
C_1p5_0402
L7
L_4n7H_0402
C44
C_2p7F_0402
C56 1nF
VDD
E1
AM11DG-ST01
7
C52
100nF
C48
C_1p2_0402
11
1
C34
C_3p3F_0402
C12
C_1u_0402
C7
C_220nF_0402
L29
120ohm
L30
0n8H
C51
C_100p_0402
C30
C_220n_0402
C33
NP
C5
C_220n_0402
CTX
R44
2.2K
23
VRDIG
CSN
2
12
C58 120pF
C22
C_220n_0402
U2
S2LP
C54
10pF
L27 2n7H
+3V3
RXP
VDD
4
VSMPS2
D
20
L13
L_18nH_0402
VDDVCOTX
C17
100pF
C39
C_12pF_0402
nW
J1
SMA ANTENNA
3
SW1
VREFVCO
C18
NM
C8
C_100p_0402
14
SMPS2
RX
3
L8
L_15nH_0402
CSD
C40
12pF
TX
1
VCC1
C13
C_100p_0402
C2
C_220n_0402
SCL
VDDRXDIG
L29
120ohm
Q
2
SDO
SCLK
C2
C_220n_0402
R43
2.2K
C60
NP
C46
C_100p_0402
GPIO2
6
SCLK
VDDANASYNTH
4
SDI 17
L12
L_18nH_0402
C43
C_1p5F_0402
L30
0n8H
U5
STSAFE-A100
OUT
L25 4n7H
5
C47
C_100p_0402
VDD
SDN
U2
S2LP
C39
C_12pF_0402
C53
10uF/0805
C38
NP
SCL
C3
C_100p_0402
C4
C_100p_0402
6
VDDSMPS
L28
6n8H
3
XIN
TX_IN
5
11
3
C49
C_1p5_0402
RX
Y1
CRYSTAL_NX1612SA
J1
SMA ANTENNA
L11
L_27nH_0402
+3V3
R43
2.2K
3
LNA_IN
2
6
UM2641 - Rev 1 page 9/20
UM2641
Schematic diagrams

Figure 5. X-NUCLEO-S2915A1 circuit schematic - Arduino connectors
1
CN9
CSN
D6
7
CN5
SDA
GPIO3
PC7
+5V
1
3V3 4
A0 1
PWM/D10
4
IOREF
D7
8
SCL
SDN
AREF
9SDA
nS
R14
NM
+3V3
3
PWM/D9
3
R7
8
PA3
R13
R9
SCL
10
0
CSN
R16
NM
8 pass-through:
male on bottom
and female on top
0
6
GND
2
R18
7
GND
PA2
JUMPER
nS
0
A4 5
SDI
1
0
5V 52SCK/D13
7GND
MOSI/PWM/D11
5
SDO
0PC7
RESET
R12
R15
6
D5
6
NC 1
D11
Pass-through:
male on bottom
and female on top
ARDUINO UNO R3 SX connector
CN8
NM
JP1
MISO/D12
6
D8
D4
5
RESET 2
R23
A5
0
D2
3
VDD
A3 4
RXD/D0
2
SCLK
R10
NM
GPIO1
330
GPIO0
A2 3
TXD/D1
SCLK
SDN
NM
0
VIN
GPIO0
R6
LED
GPIO2
AVDD
D3
4
0
IOREF
0
R11
R19
8
VIN
CN6
A1 2
0
ARDUINO UNO R3 DX connector
R4
R5
R17
Pass-through:
male on bottom
and female on top
R18
NM
6 pass-through:
male on bottom
and female on top
Figure 6. X-NUCLEO-S2915A1 circuit schematic - ST morpho connectors
PC11
PD2
E5V
IOREF
RESET
+3V3
+5V
VIN
PA0
PA1
PA4
PB0
PC1
PC0
PC9
PB8
PB9
AVDD
PA5
PA6
PA7
PB6
PC7
PA9
PA8
PB10
PB4
PB5
PB3
PA10
PA2
PA3 NC/PF4
NC/PF5
PC4
AGND
PB13
PB14
PB15
PB1
PB2
PC10
PC12
PB11/NC
VDD
BOOT0
PB12
NC/PF6
NC/PF7
PA11PA13
PA14
PA12
PA15
PD8
PB7
PC14
PC6
PC8
PC2
PC3
CN10
1
13
15
17
19
21
23
25
27
29
31
33
35
37
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
CN7
13
15
17
19
21
23
25
31
33
PH0/PF0/PD0
29
35
PH1/PF1/PD1
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
ST morpho SX connector
Pass-through:
female on bottom
and male on top
ST morpho DX connector
3
5
7
9
11
2
4
6
8
2
4
6
8
1
3
5
7
9
11
27
37
PC13
VDD
PC15
VLCD/VBAT
PC5
U5V
Pass-through:
female on bottom
and male on top
UM2641 - Rev 1 page 10/20
UM2641
Schematic diagrams