94 lines
3.1 KiB
ReStructuredText
94 lines
3.1 KiB
ReStructuredText
.. _samples_boards_nrf_dynamic_pinctrl:
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Dynamic Pin Control (nRF)
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#########################
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The Dynamic Pin Control (nRF) sample demonstrates how to change ``uart0`` at
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early boot stages, depending on the input level on a pin connected to a
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push-button.
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Overview
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********
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Slightly different board revisions that implement just small changes (like
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improving the PCB layout or changing components to new equivalents) do not
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necessarily require changes to the firmware. As such, one firmware image can be
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able to boot onto multiple board revisions.
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However, if a certain peripheral is routed to different sets of pins between
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revisions, the firmware needs to select the appropriate routing when the
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system is initialized.
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The Dynamic Pin Control (nRF) sample allows you to select the appropriate routing.
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If the push button is not pressed, the system does nothing and continues with
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the default configuration. If the button is pressed, the alternative
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configuration is applied.
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Alternative configurations can only be applied if the device driver using the
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associated pins has not been initialized yet. Therefore, pay attention to the
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initialization priorities set in the :file:`prj.conf` file.
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nRF52840 DK
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===========
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The diagram below shows the pins assigned to the default and alternative
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configurations.
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.. figure:: images/nrf52840dk-dynamic-pinctrl.png
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Configuration for nRF52840 DK
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If you power on the board, the ``uart0`` peripheral is routed to the default
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set of pins. The default set of pins is also exposed through the left USB
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connector as a virtual COM port.
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If you power on the board while holding Button 1, the ``uart0`` peripheral is
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routed to the alternative set of pins.
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Building and Running
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********************
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You can build this application for the nRF52840 DK as follows:
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.. zephyr-app-commands::
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:zephyr-app: samples/boards/nrf/dynamic_pinctrl
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:board: nrf52840dk_nrf52840
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:goals: build
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:compact:
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The sample can also support other nRF based boards if you provide a Devicetree
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overlay file with an alternative configuration for ``uart0``. Select ``uart0``
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for ``zephyr,console`` to make the sample work as expected.
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Sample Output
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=============
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Follow these steps to test the two configurations :
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1. Connect a USB-to-UART adapter to both sets of pins. If the board routes the
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default configuration to a virtual COM port (as in the nRF52840 DK), you can
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directly use that port.
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#. Open two serial terminals, one connected to the default set of pins and the
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other connected to the alternative set of pins.
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.. figure:: images/terminals-empty.png
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Two serial terminals (left: default, right: alternative).
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#. Turn on the board. You should see a ``Hello World!`` message printed on
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the first terminal.
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.. figure:: images/terminals-default.png
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``Hello World!`` printed on the default set of pins.
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#. Press and hold the configuration-selection push-button (button 1 on the
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nRF52840 DK) and press the board reset button. You now should see a
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``Hello World!`` message on the second terminal.
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.. figure:: images/terminals-alt.png
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``Hello World!`` printed on the alternative set of pins.
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