STMicroelectronics® Nucleo-WL55JC

The ST Nucleo-WL55JC (board reference MB1389) is STMicroelectronics' official evaluation board for the STM32WL. NUCLEO-WL55JC1 is built for the high frequency band (approximately 865–928 MHzMHz (Megahertz). A unit of frequency equal to one million hertz (cycles per second), used to specify the operating frequency of LoRa devices in the Meshtastic network, affecting range and data rate.) and NUCLEO-WL55JC2 for the low band (approximately 433–510 MHzMHz (Megahertz). A unit of frequency equal to one million hertz (cycles per second), used to specify the operating frequency of LoRa devices in the Meshtastic network, affecting range and data rate.). The two share a board design but wire out different RFRF (Radio Frequency). The radio signal a node transmits and receives over LoRa. paths and matching networks, so they are not interchangeable. It carries an onboard ST-LINK, so no external programmer is needed.

Specifications

• MCUMCU (Microcontroller Unit). The microcontroller that runs the firmware on a device. The hardware tables list the MCU for each supported board.
  • STM32WL55JC (Arm Cortex-M4 application core, 256 kB flash, 64 kB RAM)
• LoRaLoRaA low-power, long-range wireless communication technology used by Meshtastic devices to enable communication over distances of several kilometers without the need for cellular, Wi-Fi, or other traditional network infrastructures. Transceiver
  • STM32WL integrated sub-GHz radio (Semtech SX126x-based), 32 MHzMHz (Megahertz). A unit of frequency equal to one million hertz (cycles per second), used to specify the operating frequency of LoRa devices in the Meshtastic network, affecting range and data rate. TCXO
• Frequency options
  • NUCLEO-WL55JC1: high band (~865–928 MHzMHz (Megahertz). A unit of frequency equal to one million hertz (cycles per second), used to specify the operating frequency of LoRa devices in the Meshtastic network, affecting range and data rate.)
  • NUCLEO-WL55JC2: low band (~433–510 MHzMHz (Megahertz). A unit of frequency equal to one million hertz (cycles per second), used to specify the operating frequency of LoRa devices in the Meshtastic network, affecting range and data rate.)
• Antenna
  • Single band-specific SMASMAA threaded coaxial connector for attaching an external antenna. RP-SMA is the reverse-polarity variant, which is not interchangeable with it. connector
• Connectors
  • USBUSB (Universal Serial Bus). The wired connection used to power a device, flash firmware onto it, and communicate with it over serial. Micro-B (ST-LINK)
  • Arduino UNO V3 headers
  • ST morpho headers
• Debug
  • Onboard STLINK-V3E: SWDSWD (Serial Wire Debug). A two-pin debug and programming interface, used on STM32 devices to enter bootloader mode and flash firmware. debug, Virtual COM Port, and drag-and-drop mass-storage programming
• Controls
  • 3 user LEDsLED (Light-Emitting Diode). An indicator light on a device. The External Notification module can drive one in response to mesh activity. (green/blue/red)
  • 3 user buttons (B1/B2/B3) and a reset button
  • BOOT0 jumper (JP3)

Meshtastic pin mapping

Taken from the Meshtastic nucleo_wl55jc firmware variant. The Arduino UNO V3 headers (CN5 / CN8 / CN9) bring out a subset of the MCUMCU (Microcontroller Unit). The microcontroller that runs the firmware on a device. The hardware tables list the MCU for each supported board. pins; the ST morpho headers (CN7 / CN10) bring out every MCUMCU (Microcontroller Unit). The microcontroller that runs the firmware on a device. The hardware tables list the MCU for each supported board. pin.

Function	Pin(s)	Arduino	Morpho	Meshtastic role
Console	ST-LINK Virtual COM Port (PA2 / PA3)	-	-	Default Serial (debug output and CLICLI (Command Line Interface). A text-based interface used for interacting with software or devices like Meshtastic.)
GPSGPS (Global Positioning System). A satellite positioning system. A node with a GPS module determines its own location and can report that position to the mesh. UARTUART (Universal Asynchronous Receiver-Transmitter). A serial interface used to communicate with a device over its pins or through a USB-to-serial bridge.	PB6 (TXTX (Transmit). The transmitting of data over the radio link.), PB7 (RXRX (Receive). The receiving of data over the radio link.) — D1 / D0	✅	✅	Serial2 (GPS_SERIAL_PORT=Serial2)
I2CI2CA two-wire bus used to attach peripherals such as sensors and displays to a device.	PA11 (SDA), PA12 (SCL) — D14 / D15	✅	✅	Sensors
SPISPI (Serial Peripheral Interface). A bus used between the microcontroller and peripherals such as the LoRa radio and the display.	PA7 (MOSI), PA6 (MISO), PA5 (SCK) — D11 / D12 / D13	✅	✅	Spare SPISPI (Serial Peripheral Interface). A bus used between the microcontroller and peripherals such as the LoRa radio and the display. bus
Green LEDLED (Light-Emitting Diode). An indicator light on a device. The External Notification module can drive one in response to mesh activity.	PB9	-	✅	LED_POWER
Red LEDLED (Light-Emitting Diode). An indicator light on a device. The External Notification module can drive one in response to mesh activity.	PB11	-	✅	LoRaLoRaA low-power, long-range wireless communication technology used by Meshtastic devices to enable communication over distances of several kilometers without the need for cellular, Wi-Fi, or other traditional network infrastructures. activity
Blue LEDLED (Light-Emitting Diode). An indicator light on a device. The External Notification module can drive one in response to mesh activity.	PB15	-	✅	Notification
Button B1	PA0 (WKUP-capable)	-	✅	Main button
Button B2	PA1	-	✅	Alternate button
Button B3	PC6	-	✅	Cancel button
VBAT sense	AVBAT (internal ADCADC (Analog-to-Digital Converter). A circuit that turns a varying voltage into a digital value. Devices use one to read sensors and to measure battery voltage. channel)	-	-	BATTERY_PIN, but VBAT is tied to 3V3 by default (SB21) so this reads the rail, not a battery

Flashing

Everything runs through the onboard ST-LINK, including drag-and-drop of firmware-nucleo_wl55jc-X.X.X.xxxxxxx.bin onto the board's USBUSB (Universal Serial Bus). The wired connection used to power a device, flash firmware onto it, and communicate with it over serial. mass-storage drive.

• Flashing over SWD

Resources

• Firmware file: firmware-nucleo_wl55jc-X.X.X.xxxxxxx.bin
• NUCLEO-WL55JC product page
• UM2592: STM32WL Nucleo-64 board (MB1389) user manual