The NuMaker-LoRaD-M252 is a development board for Nuvoton NuMicro® M252 microcontrollers with LoRa module. The NuMaker-LoRaD-M252 consists of two parts: a M252 platform and an on-board Nu-Link2-Me debugger and programmer. The NuMaker-LoRaD-M252 is designed for project evaluation, prototype development and validation with power consumption monitoring function for LoRa application.

M251/M252 Series Microcontroller Features

The NuMicro® M251/M252 series is a low-power microcontroller platform based on Arm® Cortex®-M23 core for Armv8-M architecture. It runs up to 48 MHz with 32 ~ 256 Kbytes embedded Flash memory and 8 ~ 32 Kbytes embedded SRAM, 4 Kbytes Flash loader memory (LDROM) for In-System Programming (ISP). The 32-bit low-power microcontrollers supports wide supply voltage from 1.75V ~ 5.5V and operating temperature range from -40℃ ~ +105℃. Furthermore, the M251/M252 series also provides high-performance connectivity peripheral interfaces such as PSIO, UART, SPI, I2C, GPIOs, USB, a 1 MSPS DAC and a 880 kSPS ADC for sensing data from sensor devices to fulfill a variety of application scenarios. Its low-power and high-performance connectivity features strengthen the innovation of IoT.


  • M252KG6AE based on Arm® Cortex®-M23 core

Operating Characteristics

  • Running up tp 48 MHz
  • Voltage range: 1.75V to 5.5 V
  • Temperature range: -40°C to +105°C


  • Up to 256 KB of dual bank flash memory
  • Up to 32 KB SRAM

NuMaker-LoRaD-M252 Board Features

The M252 platform is based on NuMicro® M252KG6AE. For the development flexibility, the M252 platform provides the extension connectors of M252KG6AE, LoRa module, the Arduino UNO compatible headers and able to adopt multiple power supply. Furthermore, the Nuvoton-designed ammeter connector can measure the power consumption instantly, which is essential for the prototype evaluation.

In addition to the M252 platform, there is an attached on-board debugger and programmer “Nu-Link2-Me”. The Nu-Link2-Me supports on-chip debugging, online and offline ICP programming via SWD interface. The Nu-Link2-Me supports virtual COM (VCOM) port for printing debug messages on PC. Besides, the programming status could be shown on the built-in LEDs. Lastly, the Nu-Link2-Me could be detached from the development board and becoming a stand-alone mass production programmer.

  • On-board Nu-Link2-Me ICE Bridge (Mass storage as USB Disk drive) for drag and drop programming
  • M252 extended interface connectors
  • On-board LoRa module: There are two order numbers to select LoRa module type.
    • NK-LDHM252: RYLR890 for 868/915 MHz
    • NK-LDLM252: RYLR400 for 433/470 MHz
  • Ammeter connector for measuring the microcontroller’s power consumption
  • Arduino UNO compatible extension connectors
  • Fixable board power supply: External VDD power connector/Arduino UNO compatible extension connector Vin/USB FS connector/ICE USB connector on Nu-Link2-Me
  • One push-button is for reset
  • One LED for user-defined

Front View /media/uploads/cyliang/m252-front.png

Rear View /media/uploads/cyliang/m252-rear.png

Arduino UNO Compatible Interface

/media/uploads/cyliang/m252-uno-pin.png /media/uploads/cyliang/m252-uno-d-pin.png /media/uploads/cyliang/m252-uno-a-pin.png


  • Integrated Nu-Link2 Me USB debugger/emulator with debug out functionality
  • Supports mbed drag-and-drop programming and virtual COM port

Windows serial port driver

  • NuMaker USB Driver (including Nu-Link) DOWNLOAD

The Nuvoton mbed NuMaker boards are fitted with the M485SIDAE MCU running the DAPLink interface firmware to provide three main functions over a single physical USB connection.

  • USB disk “drag and drop” programming – ideal for fast prototyping or in-field upgradable products.
  • Debug interface using the Nu-Link – provides full debug capability with tools like Keil MDK.
  • USB serial interface between the host computer and the target.

Upgrade Procedure

For Windows/Linux/MacOS and other platforms

  • Set MSG switch (No.4 of ISW1 on ICE) to ON. (It should be default at ON position) /media/uploads/hyyu/msgon3.png
  1. Download NuMaker ICE firmware file Download
  2. Keep pressing DAP button and connect the USB port to your PC. A Nu_Link2 drive will be mounted. (Not Mbed drive) /media/uploads/cyliang/nu_link2_b.png
  3. Copy the "NuLink2FW.bin" to the Nu-Link2 drive.
  4. When the duplication is done, disconnect USB
  5. Done.

As While DAP Button Not Work

  1. Browse new ICP programming tool from Programming Software
  2. Choose and download new ICP tool, fox ex
  3. Install ICP tool
  4. Open ICP tool -> choose M251 series -> press connect -> choose to upgrade as new version, for ex v7091 -> Close ICP tool
  5. You could see “NuMicro” disk drive in mass mode and see “Nu-Link2” drive as while keep pressing DAP button

Technical references

Known issues

General issues are tracked into the Mbed OS Github repository

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