ST UM2708 User manual

Introduction
The B-L4S5I-IOT01A Discovery kit for the IoT node allows the user to develop applications with a direct connection to the cloud
servers.
The B-L4S5I-IOT01A Discovery kit for the IoT node enables a wide diversity of applications by exploiting low-power
multilink communication (Bluetooth® Low Energy, Wi‑Fi®, NFC), multiway sensing (detection, environmental awareness) and
Arm® Cortex®-M4 core-based STM32L4+ Series features.
ARDUINO® Uno V3 and Pmod™ connectivity provide unlimited expansion capabilities with a large choice of specialized add-on
boards.
The B-L4S5I-IOT01A Discovery kit for the IoT node includes an ST-LINK debugger/programmer and comes with the
comprehensive STM32CubeL4 MCU Package, which provides an STM32 comprehensive software HAL library as well as
various software examples to seamlessly connect to cloud servers.
Figure 1. B-L4S5I-IOT01A Discovery kit for the IoT node
Picture is not contractual.
Discovery kit for IoT node, multi-channel communication with STM32L4+ Series
UM2708
User manual
UM2708 - Rev 2 - December 2021
For further information contact your local STMicroelectronics sales office. www.st.com

1Features
• Ultra-low-power STM32L4+ Series STM32L4S5VIT6 microcontroller based on the Arm® Cortex®-M4 core
with 2 Mbytes of Flash memory and 640 Kbytes of RAM in LQFP100 package
• 64-Mbit Quad-SPI Flash memory from Macronix™
• Bluetooth® 4.1 module (SPBTLE-RF) from STMicroelectronics
• 802.11 b/g/n compliant Wi‑Fi® module (ISM43362-M3G-L44) from Inventek Systems
• Dynamic NFC TAG based on ST25DV04K with its printed NFC antenna
• 2 digital omnidirectional microphones ((I)MP34DT0x) from STMicroelectronics
• Capacitive digital sensor for relative humidity and temperature (HTS221) from STMicroelectronics
• High-performance 3-axis magnetometer (LIS3MDL) from STMicroelectronics
• 3D accelerometer and 3D gyroscope (LSM6DSL) from STMicroelectronics
• 260-1260 hPa absolute digital output barometer (LPS22HB) from STMicroelectronics
• Time-of-flight and gesture-detection sensor (VL53L0X) from STMicroelectronics
• Highly-secure solution (STSAFE-A110) from STMicroelectronics
• 2 push-buttons (user and reset)
• USB OTG FS with Micro-AB connector
•ARDUINO® Uno V3 expansion connector
• Pmod™ expansion connector
• Flexible power-supply options: ST-LINK USB VBUS, USB connector, or external sources
• On-board ST-LINK/V2-1 debugger/programmer with USB re-enumeration capability: mass storage, Virtual
COM port, and debug port
• Comprehensive free software libraries and examples available with the STM32Cube MCU Package
• Support of a wide choice of Integrated Development Environments (IDEs) including IAR Embedded
Workbench®, MDK-ARM, and STM32CubeIDE
Note: Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.
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Features
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2Ordering information
To order the B-L4S5I-IOT01A Discovery kit for the IoT node, refer to Table 1. Additional information is available
from the datasheet and reference manual of the target STM32.
Table 1. Ordering information
Order code Board reference Target STM32
B-L4S5I-IOT01A MB1297 STM32L4S5VIT6
2.1 Codification
The meaning of the codification is explained in Table 2.
Table 2. Codification explanation
B-L4S5I-IOT01A Description B-L4S5I-IOT01A
B Discovery kit with a variety of sensors Sensor node
L4S5 MCU product line in STM32 32-bit Arm Cortex MCUs STM32L4R5/S5 in the STM32L4+ Series
ISTM32 Flash memory size:
• I for 2 Mbytes 2 Mbytes
IOT Dedicated to IoT applications Discovery kit for IoT applications
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Ordering information
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3Development environment
The B-L4S5I-IOT01A Discovery kit for the IoT node runs with the STM32L4S5VI 32-bit microcontroller based on
the Arm® Cortex®-M4 core.
3.1 System requirements
• Multi‑OS support: Windows® 10, Linux® 64-bit, or macOS®
• USB Type-A or USB Type-C® to Micro-B cable
Note: macOS® is a trademark of Apple Inc. registered in the U.S. and other countries.
Linux® is a registered trademark of Linus Torvalds.
All other trademarks are the property of their respective owners.
3.2 Development toolchains
• IAR Systems® - IAR Embedded Workbench®(1)
• Keil® - MDK-ARM(1)
• STMicroelectronics - STM32CubeIDE
1. On Windows® only.
3.3 Demonstration software
The demonstration software, included in the STM32Cube MCU Package corresponding to the on-board
microcontroller, is preloaded in the STM32 Flash memory for easy demonstration of the device peripherals in
standalone mode. The latest versions of the demonstration source code and associated documentation can be
downloaded from www.st.com.
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Development environment
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4Conventions
Table 3 provides the conventions used for the ON and OFF settings in the present document.
Table 3. ON/OFF convention
Convention Definition
Jumper JPx ON Jumper fitted
Jumper JPx OFF Jumper not fitted
Jumper JPx [1-2] Jumper fitted between Pin 1 and Pin 2
Solder bridge SBx ON SBx connections closed by 0 Ω resistor
Solder bridge SBx OFF SBx connections left open
Resistor Rx ON Resistor soldered
Resistor Rx OFF Resistor not soldered
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Conventions
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5Delivery recommendations
Before first use, check the board for any damage that might have occurred during shipment, that all socketed
components are firmly fixed in their sockets and that none are loose in the plastic bag.
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Delivery recommendations
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6Hardware layout and configuration
The B-L4S5I-IOT01A Discovery kit for the IoT node is designed around the STM32L4S5VIT6 target
microcontroller in a 100-pin LQFP package. The hardware block diagram (Refer to Figure 2) illustrates the
connection between the STM32 and peripherals: embedded ST-LINK, ARDUINO® Uno V3 shields, Pmod™
connector, Quad-SPI Flash memory, USB OTG connectors, digital microphones, various ST-MEMS sensors,
and the three RF modules (Wi‑Fi®, Bluetooth®, and NFC). Figure 3 and Figure 4 help users to locate these
features on the B-L4S5I-IOT01A Discovery kit for the IoT node. Figure 5 gives the mechanical dimensions of the
B-L4S5I-IOT01A Discovery kit for the IoT node.
Figure 2. Hardware block diagram
STM32L4S5VIT6
(I)MP34DT0x digital microphone
RTC
SWD
3.3 V Power
supply
32 KHz Crystal
ST-LINK /
V2-1
GPIOs and
UART3
DFSDM
ISM43362-M3G-L44
Wi-Fi® module
PmodTM (2A) connector
PmodTM (4A) connector
LEDs,
reset and wake-up
buttons
GPIOs
GPIOs and
SPI2
GPIOs and
UART2
HS PHY and
Micro-AB USB
connector
OTG FS
QSPI
64-Mbit Quad-SPI Flash
(MX25R6435F)
VCP UART1
ARDUINO® UNo
Shield connectors
GPIOs,
UART4,
and SPI1
Micro-B
USB
connector
GPIOs and
SPI3
SPBTLE-RF
Bluetooth® module
SPSGRF Sub-GHz
(Spirit) module
Not fitted
ST25DV04K NFC
module
GPIOs and
I2C2
LIS3MDL
3-axis magnetometer
LSM6DSL
3D gyroscope
LPS22HB
digital barometer
HTS221
humidity and temperature
VL53L0X
ToF and gesture
detection
STSAFE-A110
authentication and
security
(I)MP34DT0x digital microphone
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Hardware layout and configuration
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Figure 3. B-L4S5I-IOT01A Discovery kit for the IoT node layout (top view)
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Figure 4. B-L4S5I-IOT01A Discovery kit for the IoT node layout (bottom view)
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Figure 5. B-L4S5I-IOT01A Discovery kit for the IoT node mechanical drawing in millimeters
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6.1 Embedded STLINK/V2-1
The ST-LINK/V2-1 programming and debugging tool is integrated on the B-L4S5I-IOT01A Discovery kit for the IoT
node. Compared to the ST-LINK/V2 the changes are listed below.
The new features supported on the ST-LINK/V2-1 are:
• USB software re-enumeration
• Virtual COM port interface on USB
• Mass storage interface on USB
• USB power management request for more than 100 mA power on USB
The following features are no more supported on the ST-LINK/V2-1:
• SWIM interface
• Application voltage lower than 3 V
For all general information concerning debugging and programming features common between V2 and V2-1
versions, refer to user manual ST-LINK/V2 in-circuit debugger/programmer for STM8 and STM32 (UM1075) at the
www.st.com website.
6.1.1 Drivers
The ST-LINK/V2-1 requires a dedicated USB driver, which, for Windows 7®, Windows 8® and Windows 10®, is
found at www.st.com.
In case the B-L4S5I-IOT01A Discovery kit for the IoT node is connected to the PC before the driver is installed,
some Discovery board interfaces may be declared as “Unknown” in the PC device manager. In this case, the user
must install the dedicated driver files, and update the driver of the connected device from the device manager as
shown in Figure 6.
Note: Prefer using the “USB Composite Device” handle for a full recovery.
Figure 6. USB composite device
6.1.2 ST-LINK/V2-1 firmware upgrade
The ST-LINK/V2-1 embeds a firmware upgrade mechanism for the in-situ upgrade through the USB port. As the
firmware may evolve during the lifetime of the ST-LINK/V2-1 product (for example new functionalities, bug fixes,
support for new microcontroller families), it is recommended to visit the www.st.com website before starting to use
the B-L4S5I-IOT01A Discovery kit for the IoT node and periodically, to stay up-to-date with the latest firmware
version.
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Embedded STLINK/V2-1
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6.2 Power supply
The B-L4S5I-IOT01A Discovery kit for the IoT node is designed to be powered by a 5 V DC power supply. It is
possible to configure the B-L4S5I-IOT01A Discovery kit for the IoT node to use any of the following five sources
for the power supply: 5V_ST_LINK, 5V_ARD, 5V_USB_FS, 5V_VBAT, and 5V_USB_CHARGER.
In the case of an external 5 V DC power adapter, the B-L4S5I-IOT01A Discovery kit for the IoT node must be
powered by a power supply unit or by a piece of auxiliary equipment complying with the standard EN-60950-1:
2006+A11/2009, and must be SELV (Safety extra‑low voltage) with limited power capability.
5V_ST_LINK
(Refer to Figure 7)
This is a 5V DC power with limitation from CN7, the USB type Micro-B connector of ST-LINK/V2-1. In this case,
the JP4 jumper must be fitted between pin 1 and pin 2 to select the 5V_ST_LINK power source on the JP4
silkscreen. This is the default setting. If the USB enumeration succeeds, the 5V_ST_LINK power is enabled,
by asserting the PWR_ENn signal (from STM32F103CBT6). This pin is connected to a power switch ST890,
which powers the board. This power switch features also a current limitation to protect the PC in case of an
onboard short-circuit (Current higher than 750 mA). The B-L4S5I-IOT01A Discovery kit for the IoT node can
be powered from the ST-LINK USB connector CN7, but only the ST-LINK circuit has the power before USB
enumeration because the host PC only provides 100 mA to the board at that time. During the USB enumeration,
the B-L4S5I-IOT01A Discovery kit for the IoT node asks for the 500 mA power to the host PC. If the host
can provide the required power, the enumeration finishes by a SetConfiguration command, and then, the power
transistor ST890 is switched ON, the red LED LD7 is turned ON, thus the B-L4S5I-IOT01A Discovery kit for
the IoT node consumes up to 500 mA current, but no more. If the host cannot provide the requested current,
the enumeration fails. Therefore the ST890 remains OFF and the MCU part including the extension board is
not powered. As a consequence, the red LED LD7 remains turned OFF. In this case, it is mandatory to use an
external power supply.
Figure 7. JP4: 5V_ST_LINK selection
12
3
5
7
4
6
8
109
5V_ST_LINK
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_CHARGER
JP4
5V_ARD
(Refer to Figure 8)
This is the 7 to 12 V DC power from ARDUINO® CN2 pin 8 (named VIN on ARDUINO® connector silkscreen).
In this case, the JP4 jumper must be fitted between pin 3 and pin 4 to select the 5V_ARD power source on the
JP4 silkscreen and the DC power comes from the power supply through the ARDUINO® Uno V3 battery shield
(compatible with Adafruit PowerBoost 500 shield).
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Power supply
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Figure 8. JP4: 5V_ARD selection from CN6 (VIN)
12
3
5
7
4
6
8
109
5V_ST_LINK
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_CHARGER
JP4
5V_USB_FS
(Refer to Figure 9)
This is the DC power with a 500 mA limitation from CN9, the USB OTG FS Micro-AB connector. In this case, the
JP4 jumper must be fitted between pin 5 and pin 6 to select the 5V_USB_FS power source on the JP4 silkscreen.
Figure 9. JP4: 5V_USB_FS
12
3
5
7
4
6
8
109
5V_ST_LINK
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_CHARGER
JP4
5V_VBAT
(Refer to Figure 10)
This is the DC power coming from an external source. In this case, the JP4 jumper must be fitted between pin 7
and pin 8 to select the 5V_VBAT power source on JP4 silkscreen.
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Power supply
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Figure 10. JP4: 5V_VBAT
12
3
5
7
4
6
8
109
5V_ST_LINK
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_CHARGER
JP4
5V_USB_CHARGER
(Refer to Figure 11)
This is the DC power charger connected to the USB ST-LINK (CN7). To select the 5V_USB_CHARGER power
source on the JP4 silkscreen, the JP4 jumper must be fitted between pin 9 and pin 10. In this case, if the
B-L4S5I-IOT01A Discovery kit for the IoT node is powered by an external USB charger, then the debug is not
available. If the PC is connected instead of the charger, the limitation is no longer effective and the PC may be
damaged.
Figure 11. JP4: 5V_USB_CHARGER selection
12
3
5
7
4
6
8
109
5V_ST_LINK
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_CHARGER
JP4
Note: If the board is powered by a USB charger, there is no USB enumeration, so the LD7 LED remains OFF
permanently and the board is not powered. In this specific case only, the resistor R30 must be soldered, to allow
the board to be powered anyway.
Caution: Do not connect the PC to the ST-LINK (CN7) when R30 is soldered. The PC may be damaged or the board may
not be powered correctly.
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Power supply
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The green LED LD5 is lit when the B-L4S5I-IOT01A Discovery kit for the IoT node is powered by the 5 V correctly.
The power tree is shown in Figure 12. Power tree.
Figure 12. Power tree
USB_ST_LINK
USB_OTG_FS
ARDUINO®
STM32F103 ST_LINK
Bi-color LED
ST_LINK debug
TAG
MCU STM32L4S5VIT6
64-Mbit QSPI Flash
(MX25R6435F)
(I)MP34DT0x digital microphone
ISM43362-M3G-L44
Wi-Fi® module
Bluetooth® module
SPSGRF Sub-GHz
(Spirit) module
Not Fitted
ST25DV04K NFC module
LIS3MDL
3-axis magnetometer
LSM6DSL
3D gyroscope
LPS22HB
digital barometer
HTS221
humidity and temperature
VL53L0X
ToF and gesture detection
STSAFE-A110
authentication and security
(I)MP34DT0x digital microphone
LDO
LD1117S33TR
3V3
5V
VDD_MCU
JP5
IC14
JP4
3V3_Wifi
LDO
LT1963EST-3.3
5V
IC12
Pmod™
Power switch 5V/1.2A
ST890CDR
IC17
LDO
LD3985M33R
IC16
5V_ST_Link
5V_ARD
5V_USB_FS
5V_VBAT
5V_USB_charger
LDO
LD1117S50TR
U13
VIN 5V
VDDA
5V_ARD
3V3
5V_ARD
5V_USB_ST_Link
3V3_ST_Link
Switch 5V/1.2A
ST890CDR
IC17
5V
5V_USB_FS
VDDA
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Power supply
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6.3 Programming and debugging when the power supply is not from ST-LINK
(5V_ST_LINK)
It is mandatory to power the board first using CN2 (VIN) or CN9 (USB_FS_OTG), then to connect the USB cable
to the PC. Proceeding this way ensures that the enumeration succeeds, thanks to the external power source. The
following power sequence procedure must be respected:
1. Connect the jumper JP4 on (5V_ARD) or (5V_USB_FS).
2. Connect the external power source to CN2 in case of an ARDUINO® shield or to CN9 in case of a USB FS
host interface.
3. Check that the red LED LD5 is turned ON.
4. Connect the PC to the USB connector CN7.
If this sequence is not respected, the board may be powered by VBUS first from ST-LINK, and the following risks
may be encountered:
1. If more than 500 mA current is needed by the board, the PC may be damaged or the current can be limited
by the PC. As a consequence, the board is not powered correctly.
2. 500 mA is requested at the enumeration, so there is a risk that the request is rejected and enumeration does
not succeed if the PC cannot provide such current.
6.4 Clock source
Three clock sources are described below:
• X1 8 MHz oscillator for the STM32L4S5VI microcontroller. This clock is not implemented in a basic
configuration.
• X2 32.768 kHz crystal for the STM32L4S5VI embedded RTC
• X3 8 MHz clock from the ST-LINK MCU for the STM32L4S5VIT6 microcontroller.
6.5 Reset sources
The reset signal of the B-L4S5I-IOT01A Discovery kit for the IoT node is active LOW and the reset sources
include:
• A reset button B1
• An ARDUINO® Uno V3 shield board from CN2
• An embedded ST-LINK/V2-1
6.6 USB OTG FS
The B-L4S5I-IOT01A Discovery kit for the IoT node supports USB OTG full-speed communications via the CN9
USB Micro-AB connector.
To do this, the following components must be added by the user:
• 8 MHz crystal (at X1 position). Reference is NX3225GD-8.00M
• 8.2 pF capacitor (0402 size) at the C2 position
• 8.2 pF capacitor (0402 size) at the C4 position
• 0-ohm resistor (0402 size) at the R5 position
• 0-ohm resistor (0402 size) at the R7 position
The B-L4S5I-IOT01A Discovery kit for the IoT node can be powered by the USB connectors at 5 V DC with
500 mA current limitation. A USB power switch (IC19) is also connected to VBUS and provides power to CN9. The
green LED LD9 is lit when either:
• The power switch is ON and the B-L4S5I-IOT01A Discovery kit for the IoT node works as a USB host,
• Or VBUS is powered by another USB host when the B-L4S5I-IOT01A Discovery kit for the IoT node works as
a USB device,
The red LED LD8 is lit when an over-current occurs.
6.7 Quad-SPI NOR Flash memory
64-Mbit Quad-SPI NOR Flash memory is connected to the Quad-SPI interface of the STM32L4S5VI
microcontroller.
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Programming and debugging when the power supply is not from ST-LINK (5V_ST_LINK)
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6.8 Virtual COM port
The serial interface USART1 is directly available as a Virtual COM port of the PC connected to the ST-LINK/V2-1
USB connector CN7. The Virtual COM port settings are configured with 115200 bps, 8-bit data, no parity, one-stop
bit, and no flow control.
6.9 RF modules
Three RF interfaces are available on the B-L4S5I-IOT01A board:
1. Bluetooth® (V4.1 compliant) SPBTLE-RF module,
2. 802.11 b/g/n compliant Wi‑Fi® module ISM43362-M3G-L44 from Inventek Systems,
3. Dynamic NFC TAG based on ST25DV04K with its printed NFC antenna (Double layer inductive antenna
etched on the PCB).
6.9.1 Bluetooth® module
An M1 Bluetooth® module is implemented on the top side of the B-L4S5I-IOT01A Discovery kit for the IoT node.
This Bluetooth® module can be either:
• An SPBTLE RF module on MB1297-L4S5VI-E02 revision (BL4S5IIO01A$CU2),
• Or a BlueNRG-M0 module on MB1297-L4S5VI-E03 revision (BL4S5IIO01A$CU3).
These Bluetooth® modules are easy to use Bluetooth® smart master-slave network processor modules,
respectively compliant with Bluetooth® V4.1 for the SPBTLE RF module and Bluetooth® V4.2 for the BlueNRG-
M0 module. These Bluetooth® modules simultaneously support multiple roles and can act at the same time as
Bluetooth® Smart sensor and hub device.
The entire Bluetooth® low‑energy stack and protocol are embedded into the modules. The external host
application processor, where the application resides, is connected to the Bluetooth® module through a standard
SPI interface (SPI3 of STM32L4S5VI).
The Bluetooth® modules provide a complete RF platform in a tiny form factor (Footprint of this module is 13.5
mm x 11.5 mm). Radio, antenna, high frequency, and LPO oscillators are integrated to offer a certified solution to
optimize the time to market of the final applications.
Figure 13. SPBTLE-RF module Figure 14. BlueNRG-M0 module
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Virtual COM port
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6.9.2 Inventek Systems ISM43362-M3G-L44 (802.11 b/g/n compliant Wi‑Fi® module)
The Inventek Systems ISM43362-M3G-L44 module (M2) is implemented on the top side of the B-L4S5I-IOT01A
Discovery kit for the IoT node This module is an embedded (eS-WiFi) wireless Internet Connectivity device. The
Wi‑Fi® hardware module consists of an Arm® Cortex®-M3 STM32 host processor, an integrated antenna (or
optional external antenna), and a Broadcom Wi-Fi device. The module uses either a UART or an SPI interface
(UART3 or SPI3 of STM32L4S5VI). By default, an SPI interface is used, as the corresponding firmware (for SPI
capability) is downloaded on the Wi‑Fi® ISM43362-M3G-L44 module. The Wi‑Fi® module requires no operating
system and has a completely integrated TCP/IP stack that only requires AT commands to establish connectivity
for a wireless product. The footprint of this module is 14.5 mm x 30 mm.
Figure 15. ISM43362-M3G-L44 module
On MB1297 revision E, the firmware revision inside the Wi‑Fi® module must be C3.5.2.5.STM. The Wi‑Fi®
module maximum output power is limited to 9 dBm to fulfill FCC/IC/CE requirements. A Wi‑Fi® output power
higher than 9 dBm at the Wi‑Fi® antenna is prohibited.
Note: Since Wi
‑ Fi® and Bluetooth® Low Energy modules are using the same frequency ISM band (2.4 GHz to
2.485 GHz), the simultaneous activity of both modules may affect the RF performances of Wi
‑ Fi® or Bluetooth®
Low Energy (in terms of range or throughput).
6.9.3 Dynamic NFC TAG based on ST25DV04K with its printed NFC antenna
The ST25DV04K device is an NFC RFID TAG offering 4 Kbit of electrically erasable programmable memory
(EEPROM). ST25DV04K offers two interfaces. The first one is an I2C serial link and can be operated from a DC
power supply. The second one is an RF-link activated when ST25DV04K acts as a contactless memory powered
by the received carrier electromagnetic wave.
In I2C mode, the ST25DV04K user memory contains up to 512 bytes which could be split into four flexible and
protectable areas. In RF mode, following ISO/IEC 15693 or NFC forum type 5 recommendations, ST25DV04K
user memory contains up to 128 blocks of 4 bytes which can be split into four flexible and protectable areas.
Note: The hardware layout is ready to support a Sub-GHz low-power-programmable RF module (SPSGRF-868 or
SPSGRF-915). The footprint is implemented (M3 designation), but no module is soldered.
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RF modules
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6.10 STMicroelectronics sensors
Several STMicroelectronics sensors are available on the B-L4S5I-IOT01A Discovery kit for the IoT node and are
listed below:
• Two on-board ST-MEMS audio sensor omnidirectional digital microphones (MP34DT01)
• Capacitive digital sensor for relative humidity and temperature (HTS221)
• High-performance 3-axis magnetometer (LIS3MDL)
• 3D accelerometer and 3D gyroscope (LSM6DSL)
• 260 hPa to 1260 hPa absolute digital output barometer (LPS22HB)
• Time-of-Flight and gesture detection sensor (VL53L0X)
6.10.1 Two on-board ST-MEMS microphones ((I)MP34DT0x)
The microphones implemented on the B-L4S5I-IOT01A Discovery kit for the IoT node can be either:
• MP34DT01 on MB1297-L4S5VI-E02 revision (BL4S5IIO01A$CU2),
• Or IMP34DT05 on MB1297-L4S5VI-E03 revision (BL4S5IIO01A$CU3).
These microphones are ultra-compact, low-power, omnidirectional, digital ST-MEMS microphones built with a
capacitive sensing element and an IC interface.
On the B-L4S5I-IOT01A Discovery kit for the IoT node, there are two (I)MP34DT0x microphones: one with LR
pulled to VDD and the second with LR pulled low. DFSDM1_CKOUT and DFSDM1_DATIN2 are connected to
both. In addition, both microphones are spaced at 21 mm apart for the beamforming algorithm to work. Indeed,
several algorithm configurations are available for the user to find the best trade-off between audio output quality
and resource consumption. For more details, refer to the user manual STEVAL-IHM038V1: 3-phase BLDC/PMSM
motor drive up to 50 W, suitable for fan controllers (UM1697) on the www.st.com website.
The (I)MP34DT0x microphones are available in an HCLGA (3 mm x 4 mm x 1 mm) 4LD package, in a top-port
design, SMD-compliant, EMI-shielded package, and are guaranteed to operate over an extended temperature
range from -40 to +85 °C.
6.10.2 Capacitive digital sensor for relative humidity and temperature (HTS221)
HTS221 is an ultra-compact sensor for relative humidity and temperature. It includes a sensing element and a
mixed-signal ASIC to provide the measurement information through digital serial interfaces.
The HTS221 is available in a small top-holed cap land grid array (HLGA-6L 2 mm x 2 mm x 0.9 mm) package
guaranteed to operate over a temperature range from -40 to +120 °C.
6.10.3 High-performance 3-axis magnetometer (LIS3MDL)
LIS3MDL is an ultra-low-power high-performance three-axis magnetic sensor.
LIS3MDL includes an I2C serial bus interface, that supports standard and fast mode (100 and 400 kHz),
and an SPI serial standard interface. On the B-L4S5I-IOT01A Discovery kit for the IoT node, the I2C2 bus
from STM32L4S5VIT6 is used. LIS3MDL is available in a small thin plastic land grid array LGA-12 package
(2.0 mm x 2.0 mm x 1.0 mm) and is guaranteed to operate over an extended temperature range of -40 to +85 °C.
6.10.4 3D accelerometer and 3D gyroscope (LSM6DSL)
LSM6DSL is a system-in-package featuring a 3D digital accelerometer and a 3D digital gyroscope performing at
0.65 mA in high-performance mode and enabling always-on low-power features for an optimal motion experience
for the consumer.
The registers embedded inside the LSM6DSL may be accessed through both the I2C and SPI serial interfaces.
On the B-L4S5I-IOT01A Discovery kit for the IoT node, the I2C2 bus from STM32L4S5VIT6 is used.
LSM6DSL is available in a plastic land grid array LGA-14L (2.5x3x0.83mm).
6.10.5 260 hPa to 1260 hPa absolute digital output barometer (LPS22HB)
The absolute pressure-sensing device LPS22HB is an ultra-compact piezoresistive sensor that functions as a
digital output barometer.
The device comprises a sensing element and an IC interface that communicates from the sensing element to
the application through I2C or SPI. On the B-L4S5I-IOT01A Discovery kit for the IoT node, the I2C2 bus from
STM32L4S5VIT6 is used.
UM2708
STMicroelectronics sensors
UM2708 - Rev 2 page 19/41

6.10.6 Time-of-Flight and gesture detection sensor (VL53L0X)
VL53L0X is a new generation Time-of-Flight (ToF) laser-ranging module housed in a small package, providing
accurate distance measurement whatever the target reflectance, unlike conventional technologies. It can measure
absolute distances up to two meters, setting a new benchmark in ranging performance levels, opening the door to
various new applications.
VL53L0x is a Class 1 laser device compliant with the latest standard IEC 60825-1:2014 - 3rd edition. The laser
output remains within Class 1 limits as long as the STMicroelectronics recommended device settings are used
and the operating conditions, specified in the STM32L4+ datasheets, are respected. The laser output power must
not be increased by any means and no optics may be used to focus the laser beam. Figure 16 shows the warning
label for Class 1 laser products.
Figure 16. Label for Class 1 laser products
6.11 STSAFE-A110
STSAFE-A110 is a highly secure solution that acts as a secure element, providing authentication and data
management services to a local or remote host. It consists of a full turnkey solution with a secure operating
system running on the latest generation of secure microcontrollers. STSAFE-A110 can be integrated into IoT
(Internet of things) devices, smart-home, smart-city and industrial applications, consumer electronics devices,
consumables, and accessories.
6.12 Buttons and LEDs
The black button (B1) located on the middle left side is the reset of the STM32L4S5VIT6 microcontroller. Refer to
Figure 3. B-L4S5I-IOT01A Discovery kit for the IoT node layout (top view).
The blue button (B2) located on the top left side is available to be used as a digital input or as an alternate
wake-up function.
When the button is depressed the logic state is LOW, otherwise, the logic state is HIGH.
Two green LEDs (LD1 and LD2), located on the top middle side are available for the user. To light a LED a high
logic state HIGH must be written in the corresponding GPIO. Table 2 gives the assignment of the control ports to
the LED indicators.
UM2708
STSAFE-A110
UM2708 - Rev 2 page 20/41