This application blinks a LED using the :ref:`PWM API <pwm_api>`. See :ref:`blinky-sample` for a GPIO-based sample.
The LED starts blinking at a 1 Hz frequency. The frequency doubles every 4 seconds until it reaches 128 Hz. The frequency will then be halved every 4 seconds until it returns to 1 Hz, completing a single blinking cycle. This faster-then-slower blinking cycle then repeats forever.
Some PWM hardware cannot set the PWM period to 1 second to achieve the blinking frequency of 1 Hz. This sample calibrates itself to what the hardware supports at startup. The maximum PWM period is decreased appropriately until a value supported by the hardware is found.
The board must have an LED connected to a PWM output channel. The PWM
controlling this LED must be configured using the pwm_led0 :ref:`devicetree
<dt-guide>` alias, usually in the :ref:`BOARD.dts file
<devicetree-in-out-files>`.
No additional wiring is necessary if pwm_led0 refers to hardware that is
already connected to an LED on the board.
In these other cases, however, manual wiring is necessary:
| Board | Wiring |
|---|---|
| :ref:`nucleo_f401re_board` | connect PWM2 (PA0) to an LED |
| :ref:`nucleo_l476rg_board` | connect PWM2 (PA0) to an LED |
| :ref:`stm32f4_disco_board` | connect PWM2 (PA0) to an LED |
| :ref:`nucleo_f302r8_board` | connect PWM2 (PA0) to an LED |
| :ref:`nucleo_f103rb_board` | connect PWM1 (PA8) to an LED |
| :ref:`nucleo_wb55rg_board` | connect PWM1 (PA8) to an LED |
| :ref:`esp32` | connect GPIO2 to an LED |
| :ref:`esp32s2_saola` | connect GPIO2 to an LED |
| :ref:`esp32c3_devkitm` | connect GPIO2 to an LED |
To build and flash this sample for the :ref:`nrf52840dk_nrf52840`:
.. zephyr-app-commands:: :zephyr-app: samples/basic/blinky_pwm :board: nrf52840dk_nrf52840 :goals: build flash :compact:
Change nrf52840dk_nrf52840 appropriately for other supported boards.
After flashing, the sample starts blinking the LED as described above. It also prints information to the board's console.