This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down list at the bottom of the left panel and select the desired version.

ST Nucleo WL55JC


The NUCLEO-WL55JC STM32WL Nucleo-64 board provides an affordable and flexible way for users to try out new concepts and build prototypes with the STM32WL Series microcontroller, choosing from the various combinations of performance, power consumption, and features.

  • STM32WL55JC microcontroller multiprotocol LPWAN dual-core 32-bit (Arm® Cortex®-M4/M0+ at 48 MHz) in UFBGA73 package featuring:

    • Ultra-low-power MCU

    • RF transceiver (150 MHz to 960 MHz frequency range) supporting LoRa®, (G)FSK, (G)MSK, and BPSK modulations

    • 256-Kbyte Flash memory and 64-Kbyte SRAM

  • 3 user LEDs

  • 3 user buttons and 1 reset push-button

  • 32.768 kHz LSE crystal oscillator

  • 32 MHz HSE on-board oscillator

  • Board connectors:

    • USB with Micro-B

    • MIPI debug connector

    • ARDUINO Uno V3 expansion connector

    • ST morpho extension pin headers for full access to all STM32WL I/Os

  • Delivered with SMA antenna

  • Flexible power-supply options: ST-LINK, USB VBUS, or external sources

  • On-board STLINK-V3 debugger/programmer with USB re-enumeration capability: mass storage, Virtual COM port, and debug port

  • Comprehensive free software libraries and examples available with the STM32CubeWL MCU Package

  • Support of a wide choice of Integrated Development Environments (IDEs) including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE

  • Suitable for rapid prototyping of end nodes based on LoRaWAN, Sigfox, wM-Bus, and many other proprietary protocols

  • Fully open hardware platform

Nucleo WL55JC

More information about the board can be found at the Nucleo WL55JC website.


The STM32WL55JC long-range wireless and ultra-low-power devices embed a powerful and ultra-low-power LPWAN-compliant radio solution, enabling the following modulations: LoRa®, (G)FSK, (G)MSK, and BPSK It provides the following hardware capabilities:

  • Radio

    • Frequency range: 150 MHz to 960 MHz

    • Modulation: LoRa®, (G)FSK, (G)MSK and BPSK

    • RX sensitivity: –123 dBm for 2-FSK(at 1.2 Kbit/s), –148 dBm for LoRa® (at 10.4 kHz, spreading factor 12)

    • Transmitter high output power, programmable up to +22 dBm

    • Transmitter low output power, programmable up to +15 dBm

    • Compliant with the following radio frequency regulations such as ETSI EN 300 220, EN 300 113, EN 301 166, FCC CFR 47 Part 15, 24, 90, 101 and the Japanese ARIB STD-T30, T-67, T-108

    • Compatible with standardized or proprietary protocols such as LoRaWAN®, Sigfox™, W-MBus and more (fully open wireless system-on-chip)

  • Core

    • 32-bit Arm® Cortex®-M4 CPU

      • Adaptive real-time accelerator (ART Accelerator) allowing 0-wait-state execution from Flash memory, frequency up to 48 MHz, MPU and DSP instructions

      • 1.25 DMIPS/MHz (Dhrystone 2.1)

    • 32-bit Arm®Cortex®-M0+ CPU

      • Frequency up to 48 MHz, MPU

      • 0.95 DMIPS/MHz (Dhrystone 2.1)

  • Security and identification

    • Hardware encryption AES 256-bit

    • True random number generator (RNG)

    • Sector protection against read/write operations (PCROP, RDP, WRP)

    • CRC calculation unit

    • Unique device identifier (64-bit UID compliant with IEEE 802-2001 standard)

    • 96-bit unique die identifier

    • Hardware public key accelerator (PKA)

    • Key management services

    • Secure sub-GHz MAC layer

    • Secure firmware update (SFU)

    • Secure firmware install (SFI)

  • Supply and reset management

    • High-efficiency embedded SMPS step-down converter

    • SMPS to LDO smart switch

    • Ultra-safe, low-power BOR (brownout reset) with 5 selectable thresholds

    • Ultra-low-power POR/PDR

    • Programmable voltage detector (PVD)

    • VBAT mode with RTC and 20x32-byte backup registers

  • Clock sources

    • 32 MHz crystal oscillator

    • TCXO support: programmable supply voltage

    • 32 kHz oscillator for RTC with calibration

    • High-speed internal 16 MHz factory trimmed RC (± 1 %)

    • Internal low-power 32 kHz RC

    • Internal multi-speed low-power 100 kHz to 48 MHz RC

    • PLL for CPU, ADC and audio clocks

  • Memories

    • 256-Kbyte Flash memory

    • 64-Kbyte RAM

    • 20x32-bit backup register

    • Bootloader supporting USART and SPI interfaces

    • OTA (over-the-air) firmware update capable

    • Sector protection against read/write operations

  • Rich analog peripherals (down to 1.62 V)

    • 12-bit ADC 2.5 Msps, up to 16 bits with hardware oversampling, conversion range up to 3.6 V

    • 12-bit DAC, low-power sample-and-hold

    • 2x ultra-low-power comparators

  • System peripherals

    • Mailbox and semaphores for communication between Cortex®-M4 and Cortex®-M0+ firmware

  • Controllers

    • 2x DMA controller (7 channels each) supporting ADC, DAC, SPI, I2C, LPUART, USART, AES and timers

    • 2x USART (ISO 7816, IrDA, SPI)

    • 1x LPUART (low-power)

    • 2x SPI 16 Mbit/s (1 over 2 supporting I2S)

    • 3x I2C (SMBus/PMBus™)

    • 2x 16-bit 1-channel timer

    • 1x 16-bit 4-channel timer (supporting motor control)

    • 1x 32-bit 4-channel timer

    • 3x 16-bit ultra-low-power timer

    • 1x RTC with 32-bit sub-second wakeup counter

    • 1x independent SysTick

    • 1x independent watchdog

    • 1x window watchdog

  • Up to 43 I/Os, most 5 V-tolerant

  • Development support - Serial-wire debug (SWD), JTAG - Dual CPU cross trigger capabilities

More information about STM32WL55JC can be found here:

Supported Features

The Zephyr nucleo_wl55jc board configuration supports the following hardware features:









reset and clock_control






























serial port-polling; serial port-interrupt



ADC Controller



DAC Controller



die temperature sensor




Other hardware features are not yet supported on this Zephyr port.

The default configuration can be found in:

Connections and IOs

Nucleo WL55JC Board has 4 GPIO controllers. These controllers are responsible for pin muxing, input/output, pull-up, etc.

Default Zephyr Peripheral Mapping:

  • LPUART_1 TX/RX : PA3/PA2 (ST-Link Virtual Port Com)

  • I2C_2_SCL : PA12 (Arduino I2C)

  • I2C_2_SDA : PA11 (Arduino I2C)

  • SPI_1_NSS : PA4 (arduino_spi)

  • SPI_1_SCK : PA5 (arduino_spi)

  • SPI_1_MISO : PA6 (arduino_spi)

  • SPI_1_MOSI : PA7 (arduino_spi)

  • ADC1_IN5 : PB1 (Arduino pin A0)

  • DAC1_OUT1 : PA10 (Arduino pin A2)

System Clock

Nucleo WL55JC System Clock could be driven by internal or external oscillator, as well as main PLL clock. By default System clock is driven by HSE clock at 32MHz.

Serial Port

Nucleo WL55JC board has 2 (LP)U(S)ARTs. The Zephyr console output is assigned to LPUART_1. Default settings are 115200 8N1.

Programming and Debugging

Applications for the nucleo_wl55jc board configuration can be built the usual way (see Building an Application).


Nucleo WL55JC board includes an STLINK-V3 embedded debug tool interface. This interface is supported by the openocd version included in the Zephyr SDK since v0.11.0. You can also choose the stm32cubeprogrammer runner.

Flashing an application to Nucleo WL55JC

Connect the Nucleo WL55JC to your host computer using the USB port. Then build and flash an application. Here is an example for the Hello World application.

Run a serial host program to connect with your Nucleo board:

$ minicom -D /dev/ttyUSB0

Then build and flash the application.

# From the root of the zephyr repository
west build -b nucleo_wl55jc samples/hello_world
west flash

You should see the following message on the console:

Hello World! arm


You can debug an application in the usual way. Here is an example for the Blinky application.

# From the root of the zephyr repository
west build -b nucleo_wl55jc samples/basic/blinky
west debug