79 lines
2.3 KiB
ReStructuredText
79 lines
2.3 KiB
ReStructuredText
.. _blink-led-sample:
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.. _pwm-blinky-sample:
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PWM Blinky
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##########
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Overview
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********
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This application blinks a LED using the :ref:`PWM API <pwm_api>`. See
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:ref:`blinky-sample` for a GPIO-based sample.
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The LED starts blinking at a 1 Hz frequency. The frequency doubles every 4
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seconds until it reaches 64 Hz. The frequency will then be halved every 4
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seconds until it returns to 1 Hz, completing a single blinking cycle. This
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faster-then-slower blinking cycle then repeats forever.
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Some PWM hardware cannot set the PWM period to 1 second to achieve the blinking
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frequency of 1 Hz. This sample calibrates itself to what the hardware supports
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at startup. The maximum PWM period is decreased appropriately until a value
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supported by the hardware is found.
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Requirements
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************
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The board must have an LED connected to a PWM output channel. The PWM
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controlling this LED must be configured using the ``pwm_led0`` :ref:`devicetree
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<dt-guide>` alias, usually in the :ref:`BOARD.dts file
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<devicetree-in-out-files>`.
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You will see this error if you try to build this sample for an unsupported
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board:
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.. code-block:: none
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Unsupported board: pwm_led0 devicetree alias is not defined
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Wiring
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******
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No additional wiring is necessary if ``pwm_led0`` refers to hardware that is
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already connected to an LED on the board.
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In these other cases, however, manual wiring is necessary:
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.. list-table::
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:header-rows: 1
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* - Board
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- Wiring
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* - :ref:`nucleo_f401re_board`
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- connect PWM2 (PA0) to an LED
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* - :ref:`nucleo_l476rg_board`
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- connect PWM2 (PA0) to an LED
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* - :ref:`stm32f4_disco_board`
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- connect PWM2 (PA0) to an LED
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* - :ref:`nucleo_f302r8_board`
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- connect PWM2 (PA0) to an LED
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* - :ref:`nucleo_f103rb_board`
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- connect PWM1 (PA8) to an LED
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* - :ref:`nucleo_wb55rg_board`
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- connect PWM1 (PA8) to an LED
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Building and Running
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********************
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To build and flash this sample for the :ref:`nrf52840dk_nrf52840`:
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.. zephyr-app-commands::
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:zephyr-app: samples/basic/blinky_pwm
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:board: nrf52840dk_nrf52840
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:goals: build flash
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:compact:
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Change ``nrf52840dk_nrf52840`` appropriately for other supported boards.
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After flashing, the sample starts blinking the LED as described above. It also
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prints information to the board's console.
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