How to blink a Seeeduino XIAO onboard LED (Mac, 7 Steps)

In this article I show you how to blink the onboard LED of a Seeeduino XIAO board. These instructions were written using a Mac, but can easily be adapted for Windows.

To blink the onboard LED of a Seeeduino XIAO board you can program it like an Arduino board. Once you add support for the board to the Arduino IDE, you can write and run a simple blink example.

In the steps below, I will show you how to do that.

Where to buy

You can buy a Seeeduino XIAO from Amazon in the US using my affiliate link (this link is for a 3 pack):

The Seeeduino XIAO has a USB-C connector. So to connect it to your PC you will need one of these cables:

Step 1. Plug the Seeeduino XIAO into your Mac

The first thing that you need to do is plug the Seeeduino XIAO board into your Mac. The board will be powered by the USB cable for this example. So you won’t need an external power supply.

  • Plug the USB cable into your laptop
  • Plug the USB cable into your Seeeduino XIAO board
  • Confirm the power LED on the board is on (on my board it is a green LED)
  • Depending on how your board was configured by default an onboard LED may be blinking too
    • On my board the onboard LED is yellow

Step 2. Download the Arduino IDE

This article was tested using the Arduino IDE version 1.8.13.

Mac Instructions

  • Double click the *.zip file to extract the application
  • Copy the Arduino app to the Applications folder

Step 3: Configure the Arduino IDE for Seeeduino boards

  • Start the Arduino IDE
  • From the main menu select Arduino > Preferences…
  • For Additional Board Manager URLs enter in the field on its own line:
  • Select Tools > Board: * > Boards Manager…
  • Type in Seeeduino XIAO
  • You should see a listing for Seeed SAMD Boards
  • Click Install
  • Click Close

Step 4. Select your board and port

To select the board:

  • Select Tools > Board: *
  • Select Seeed SAMD (…) Boards
  • Select Seeed XIAO

To select the port:

  • Select Tools > Port: *
  • Select /dev/cu.usbmodem* (Seeeduino XIAO)

Step 5: Paste the code into the IDE

Paste the code below into the IDE window. It’s based on the generic Arduino blink example.

You can completely replace any existing example or setup code that is already there:

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED off (HIGH is the voltage level)
  delay(5000);                       // wait for a long time while the LED remains off
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED on by making the voltage LOW
  delay(250);                        // wait for a short time to briefly light the LED

Code description

  • The setup function sets up the onboard LED as an output pin, so it can be turned on and off
  • The loop repeatedly turns the LED off and on by toggling the voltage level between HIGH and LOW
  • Delays are used to control how quickly the LED turns off and onn

Unlike some boards, setting the LED pin HIGH turns off the onboard LED. Setting the LED pin LOW turns on the onboard LED.

Step 6: Upload the code to the Seeeduino XIAO

  • Click the Upload button (the right pointing arrow in the IDE tool bar)

Step 7: Verify it works

  • Verify that you see the onboard LED blinking on and off

On my board the LED is yellow.

The LED should blink like this:

  • LED off for 5 seconds while the builtin LED pin is HIGH
  • LED on for 250ms while the builtin LED pin is LOW

Next step

You can experiment with this simple example by changing the delay values and uploading new code to the device. Make the delay different enough so that you can confirm that your changes are working.


In this article you learned how to:

  • Connect a Seeeduino XIAO to your PC
  • Setup and install Arduino IDE support for the board
  • Set the Arduino IDE board and port to work with the board
  • Upload and run an example to blink the onboard LED

See my related articles, where I show how to blink the LED for other types of Arduino boards.


  • Seeeduino XIAO - Arduino Microcontroller - SAMD21 Cortex M0+ - Seeed Studio [1]

About the Author

Mitch Allen has worked for software companies in Silicon Valley, along Boston’s Route 128 and in New York’s Silicon Alley. He currently works for a robotics company in Massachusetts.