> After you click any link to [ESP-IDF Programming Guide](https://docs.espressif.com/projects/esp-idf/en/latest/index.html), go to the top of the sidebar, then make sure you have the appropriate **Espressif chip** (target) and **ESP-IDF version** selected in the dropdown menus.
This example shows how to use the [ESP Timer](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/esp_timer.html) feature to create timers and execute callback functions. On the linked page, you will find detailed information about the feature as well as the functions and procedures used in this example.
In addition, the [Sleep Modes](https://docs.espressif.com/projects/esp-idf/en/stable/api-reference/system/sleep_modes.html) feature is used to briefly enter light sleep. This demonstrates that timekeeping continues correctly after light sleep.
The example starts by creating and starting a periodic and a one-shot timer. Their callback functions print the time elapsed since the example was booted. Then the `oneshot_timer_callback()` function redefines the period of the periodic timer and restarts it.
After that, the chip enters light sleep for 0.5 seconds. Once the chip wakes up, the timers execute a couple of more callback functions, then the timers are stopped and deleted to free up memory.
The subsections below give only absolutely necessary information. For full steps to configure ESP-IDF and use it to build and run projects, see [ESP-IDF Getting Started](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html#get-started).
First of all, your target must be supported by both:
- **By your ESP-IDF version**: For the full list of supported targets, run:
```
idf.py --list-targets
```
- **By this example**: For the full list of supported targets, refer to the supported targets table at the top of this README.
After you make sure that your target is supported, go to your example project directory and [set the chip target](https://docs.espressif.com/projects/esp-idf/en/latest/api-guides/tools/idf-py.html#select-the-target-chip-set-target):
This example does not need configuration. The required Kconfig options differing from the ESP-IDF defaults are pre-set for this particular example in [sdkconfig.defaults](./sdkconfig.defaults).
For more information about those and other Kconfig options, see [Project Configuration](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/kconfig.html#esp-timer-high-resolution-timer) > ESP Timer (High Resolution Timer).
Timers are used to execute a callback function as a delayed action. So the callback functions `periodic_timer_callback()` and `oneshot_timer_callback()` are crucial parts of this application example.
The function `esp_timer_dump()` is used to print the timer dumps which can be useful for debugging purposes. For details, see *ESP Timer API Reference* > [Debugging Timers](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/system/esp_timer.html#debugging-timers).
To make the output of the dump function more detailed, this example's file `sdkconfig.defaults` has the option `CONFIG_ESP_TIMER_PROFILING` set (see [Configure the Project](#configure-the-project)).
To demonstrate that timekeeping continues correctly after light sleep, the example briefly enters light sleep using `esp_sleep_enable_timer_wakeup()` and `esp_light_sleep_start()`.
During light sleep, the CPU is not running, so callbacks cannot be dispatched. On wakeup, the system attempts to execute all unhandled callbacks if any, then ESP Timer resumes its normal operation.
