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 menu on the left and select the desired version.

Basic Thread Example


This example demonstrates spawning multiple threads using K_THREAD_DEFINE(). It spawns three threads. Each thread is then defined at compile time using K_THREAD_DEFINE.

The first two each control an LED. These LEDs, led0 and led1, have loop control and timing logic controlled by separate functions.

  • blink0() controls led0 and has a 100ms sleep cycle

  • blink1() controls led1 and has a 1000ms sleep cycle

When either of these threads toggles its LED, it also pushes information into a FIFO identifying the thread/LED and how many times it has been toggled.

The third thread uses printk() to print the information added to the FIFO to the device console.


The board must have two LEDs connected via GPIO pins. These are called “User LEDs” on many of Zephyr’s Supported Boards. The LEDs must be configured using the led0 and led1 devicetree aliases, usually in the BOARD.dts file.

You will see one of these errors if you try to build this sample for an unsupported board:

Unsupported board: led0 devicetree alias is not defined
Unsupported board: led1 devicetree alias is not defined


For example, to build this sample for 96Boards Carbon:

west build -b 96b_carbon samples/basic/threads
west flash

Change 96b_carbon appropriately for other supported boards.