---
title: Cygnet Quickstart
description: Learn how to get up an running with Blues Cygnet, including step debugging with Cygnet using Visual Studio Code and an STLink programmer
source_url: https://dev.blues.io/quickstart/cygnet-quickstart/
canonical_url: https://dev.blues.io/quickstart/cygnet-quickstart/
markdown_url: https://dev.blues.io/quickstart/cygnet-quickstart.md
---

# Cygnet Quickstart

In this tutorial you'll learn how to set up and flash firmware to **Cygnet**, a low-cost Feather-compatible STM32L433-based microcontroller board designed to accelerate the development and deployment of battery-powered solutions.

By the end of this guide you'll have flashed a working blink sketch to the Cygnet host. The guide covers two methods for flashing firmware—over USB and via an STLINK programmer—so you can choose the approach that works best for your setup. It also covers step debugging with the STLINK, so you can set breakpoints and inspect your firmware as it runs.

![Cygnet](https://dev.blues.io/images/quickstart/cygnet/cygnet-front.png?v=57146c3b)

> **Note:**
>
> This guide shows how to flash firmware to Cygnet using Arduino IDE because of its ease of use.
>
> After completing this quickstart tutorial, you may wish to try out one of the following alternative platforms for writing Cygnet firmware:
>
> - [Using PlatformIO with Cygnet](https://dev.blues.io/feather-mcus/cygnet/using-platformio-with-cygnet.md)
> - [Using the STM32CubeIDE with Cygnet](https://dev.blues.io/feather-mcus/cygnet/using-stm32cubeide-with-cygnet.md)

## Prerequisites

Before working with firmware in Arduino IDE, you must first complete the following prerequisites.

1. Download and install [Arduino IDE](https://www.arduino.cc/en/software/).

2. Download and install [STM32CubeCLT](https://www.st.com/en/development-tools/stm32cubeclt.html), which is a toolset that allows third-party environments to work with STM32-based host MCUs.

   > **Note:**
   >
   > Alternatively, you may install both [STM32CubeIDE](https://www.st.com/en/development-tools/stm32cubeide.html#st-get-software) and [STM32CubeProgrammer](https://www.st.com/en/development-tools/stm32cubeprog.html#get-software). These are much larger software packages that may not be necessary for your local development environment. Be sure to also follow [these installation notes](https://dev.blues.io/notecard/notecard-walkthrough/updating-notecard-firmware.md#stm32cubeprogrammer-installation-notes) when installing STM32CubeProgrammer.

**Linux-only setup required for accessing the device in DFU mode and virtual COM port.**

1. Create a `/etc/udev/rules.d/` rule for the device in DFU mode.

   ```bash
   (echo '# DFU (Internal bootloader for STM32 MCUs)';  echo 'SUBSYSTEM=="usb", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="df11", MODE="0664", GROUP="plugdev"') | sudo tee /etc/udev/rules.d/49-stdfu-permissions.rules > /dev/null
   ```

2. Create a `/etc/udev/rules.d/` rule for the device's virtual COM port.

   ```bash
   (echo '# Virtual COM Port for STM32 MCUs'; echo 'SUBSYSTEM=="usb", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="5740", MODE="0664", GROUP="plugdev"') | sudo tee /etc/udev/rules.d/49-stvcp-permissions.rules > /dev/null
   ```

3. Add active user to `plugdev` group in `/etc/group`.

   ```bash
   sudo usermod -aG plugdev $USER
   ```

**Using the Arduino CLI**

As an alternative to using Arduino IDE to configure and build your project, you can use the [Arduino CLI](https://arduino.github.io/arduino-cli/1.1/installation/).

1. In order to specify Cygnet as the board, you need to first install the STM32duino core. You'll need a minimum of version `2.9.0` of the STM32duino core installed.

   ```bash
   arduino-cli core install STMicroelectronics:stm32
   ```

2. You can then specify the Cygnet by using the board part number. For example:

   ```bash
   arduino-cli compile --fqbn STMicroelectronics:stm32:Blues:pnum=CYGNET blinky.ino
   ```

## Configuring Arduino IDE

With Arduino IDE installed, you next need to configure your environment to build and flash code to your Cygnet.

### Installing STM32duino in the Arduino IDE

1. Within Arduino IDE open your **Settings/Preferences**.

2. Locate the **Additional boards manager URLs** (see screenshot below), and add the following URL: `https://github.com/stm32duino/BoardManagerFiles/raw/main/package_stmicroelectronics_index.json`

   ![Update ArduinoIDE preferences](https://dev.blues.io/images/quickstart/swan/arduinoide-bsp-config.png?v=1b069d1b)

3. Click **OK** to save your changes, and then restart Arduino IDE.

4. Next, click the Boards Manager icon (second icon down in the left panel), search for **STM32 MCU based boards**, and install version `2.9.0` or greater. ![Board manager in Arduino IDE](https://dev.blues.io/images/quickstart/swan/arduino-board-manager.png?v=1baab9bb)

5. Restart Arduino IDE.

### Using STM32duino in the Arduino IDE

1. Under **Tools > Board**, select **STM32 MCU based boards**, and then **Blues boards**.

   ![Select STM32 Board](https://dev.blues.io/images/quickstart/swan/arduinoide-stm32-board.png?v=ca633cfb)

2. Next, under **Tools > Board part number**, select **Cygnet**.

   ![Select STM32 Board Part](https://dev.blues.io/images/quickstart/cygnet/arduinoide-stm32-board-part-cygnet.png?v=ca0b7f08)

3. Lastly, under **Tools > USB support (if available)**, select **CDC (generic 'Serial' supersede U(S)ART)**.

## Flashing Firmware

Now that you have Arduino IDE configured to work with Cygnet, you're ready to flash firmware.

To do so, we recommend using a programmer like the [STLINK-V3MINI](https://shop.blues.com/products/stlink-v3mini?utm_source=dev-blues\&utm_medium=web\&utm_campaign=store-link), however, you may also program Cygnet via a USB cable connected to your computer.

> **Tip:**
>
> **Let AI write your firmware.** Blues Expert MCP connects your AI coding assistant (Claude Code, GitHub Copilot, Cursor) directly to our API docs, providing live request validation and firmware best practices for Arduino, C, Zephyr, and Python. [Install the Blues Expert MCP →](https://dev.blues.io/tools-and-sdks/generative-ai-tools/blues-expert-mcp.md)

### Programming Cygnet *with* the STLINK-V3MINI (Recommended)

1. In Arduino IDE, under **Tools > Upload method**, select **STM32CubeProgrammer (SWD)**.

2. Plug the STLINK-V3MINI into your computer over USB.

3. Plug the Cygnet into a power source (e.g. a LiPo battery or your computer via USB).

   **NOTE:** If you want to see Serial output from the Cygnet, you need to either use a USB cable as the power source or customize your sketch to [use the STLINK-V3MINI for Serial output](https://dev.blues.io/feather-mcus/serial-logging-with-stlink.md).

4. Plug the Cortex-Debug connector from the STLINK-V3MINI into the Cygnet.

   ![cygnet to stlink](https://dev.blues.io/images/quickstart/cygnet/cygnet-stlink.jpg?v=f89f4cd9)

5. Skip to the [**Blink the Onboard LED**](#blink-the-onboard-led) instructions below.

### Programming Cygnet *without* the STLINK-V3MINI

1. In Arduino IDE, under **Tools > Upload method**, select **STM32CubeProgrammer (DFU)**.

2. Connect the Cygnet's USB-C port to your computer with a USB cable.

   ![cygnet usb c](https://dev.blues.io/images/quickstart/cygnet/cygnet-usb-c.jpg?v=7732bd57)

3. Press and hold the `BOOT` button on the Cygnet, press and release `RST` (reset), then release `BOOT` to cause the Cygnet to jump into its bootloader. This sequence **must be done every time** you want to upload firmware to the Cygnet.

4. Proceed to the **Blink the Onboard LED** instructions below.

## Blink the Onboard LED

1. In the Arduino IDE, use **File > New Sketch** to create a new sketch.

2. Overwrite the provided boilerplate code with the following to cause the onboard LED to blink repeatedly:

   ```cpp
   // the setup function runs once when you press reset or power the board
   void setup() {
     // initialize digital pin LED_BUILTIN as an output.
     pinMode(LED_BUILTIN, OUTPUT);
   }

   // the loop function runs over and over again forever
   void loop() {
     digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
     delay(1000);                       // wait for a second
     digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
     delay(1000);                       // wait for a second
   }
   ```

3. Use the **Upload** button to upload this sketch to your Cygnet.

If the Cygnet's LED blinks on and off every second—you're good to go! Follow the next section if you have an STLINK programmer and want to learn about step debugging, or move on to the [next steps](#next-steps).

## Step Debugging with Arduino IDE

Cygnet supports step debugging with [Arduino Native Debugging](https://github.com/stm32duino/Arduino_Core_STM32/wiki/How-to-debug) on Arduino IDE when used with an attached [STLINK programmer/debugger](https://shop.blues.com/collections/accessories/products/stlink-v3mini?utm_source=dev-blues\&utm_medium=web\&utm_campaign=store-link).

1. Set one or more breakpoints on your sketch.

   ![cygnet set breakpoints](https://dev.blues.io/images/quickstart/cygnet/swan-cygnet-set-breakpoint.png?v=e8c852de)

2. In the **Sketch** menu, select **Optimize for Debugging**.

   ![cygnet optimize for debugging in arduino ide](https://dev.blues.io/images/quickstart/cygnet/swan-cygnet-optimize-debug.png?v=fcdc93f1)

3. **Upload** the sketch to Cygnet.

4. Click the **Start Debugging** button.

   ![cygnet start debugging](https://dev.blues.io/images/quickstart/cygnet/swan-cygnet-start-debugging.png?v=4e4cfda7)

5. When a breakpoint is hit, use the Arduino IDE to step through relevant code blocks and inspect variables, view the call stack, and watch expressions.

   ![cygnet step debugging](https://dev.blues.io/images/quickstart/cygnet/swan-cygnet-step-debug.png?v=82456ddc)

## Next Steps

**Congratulations!** You've configured your Cygnet and flashed new firmware to it using Arduino IDE.

If you're following the a Cell+WiFi Quickstart, next we recommend building your first IoT app:

1. ~~Use the Notecard to Send Data~~
2. ~~Set Up Your Microcontroller~~
3. [Build Your First IoT App With Blues](https://dev.blues.io/guides-and-tutorials/collecting-sensor-data/blues-cygnet/c-cpp-arduino-wiring.md)
4. [Send Data to Your Cloud](https://dev.blues.io/guides-and-tutorials/routing-data-to-cloud.md)

At any time, if you find yourself stuck, please reach out on the [community forum](https://discuss.blues.com/).