121 lines
4.7 KiB
ReStructuredText
121 lines
4.7 KiB
ReStructuredText
Environment Variables
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=====================
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CircuitPython 8.0.0 introduces support for environment variables. Environment
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variables are commonly used to store "secrets" such as Wi-Fi passwords and API
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keys. This method *does not* make them secure. It only separates them from the
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code.
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CircuitPython uses a file called ``settings.toml`` at the drive root (no
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folder) as the environment. User code can access the values from the file
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using `os.getenv()`. It is recommended to save any values used repeatedly in a
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variable because `os.getenv()` will parse the ``settings.toml`` file contents
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on every access.
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CircuitPython only supports a subset of the full toml specification, see below
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for more details. The subset is very "Python-like", which is a key reason we
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selected the format.
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Due to technical limitations it probably also accepts some files that are
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not valid TOML files; bugs of this nature are subject to change (i.e., be
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fixed) without the usual deprecation period for incompatible changes.
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File format example:
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.. code-block::
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str_key="Hello world" # with trailing comment
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int_key = 7
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unicode_key="œuvre"
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unicode_key2="\\u0153uvre" # same as above
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unicode_key3="\\U00000153uvre" # same as above
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escape_codes="supported, including \\r\\n\\"\\\\"
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# comment
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[subtable]
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subvalue="cannot retrieve this using getenv"
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Details of the toml language subset
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-----------------------------------
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* The content is required to be in UTF-8 encoding
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* The supported data types are string and integer
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* Only basic strings are supported, not triple-quoted strings
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* Only integers supported by strtol. (no 0o, no 0b, no underscores 1_000, 011
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is 9, not 11)
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* Only bare keys are supported
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* Duplicate keys are not diagnosed.
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* Comments are supported
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* Only values from the "root table" can be retrieved
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* due to technical limitations, the content of multi-line
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strings can erroneously be parsed as a value.
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CircuitPython behavior
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----------------------
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CircuitPython will also read the environment to configure its behavior. Other
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keys are ignored by CircuitPython. Here are the keys it uses:
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Core CircuitPython keys
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^^^^^^^^^^^^^^^^^^^^^^^
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CIRCUITPY_BLE_NAME
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~~~~~~~~~~~~~~~~~~
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Default BLE name the board advertises as, including for the BLE workflow.
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CIRCUITPY_HEAP_START_SIZE
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~~~~~~~~~~~~~~~~~~~~~~~~~
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Sets the initial size of the python heap, allocated from the outer heap. Must be a multiple of 4.
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The default is currently 8192.
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The python heap will grow by doubling and redoubling this initial size until it cannot fit in the outer heap.
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Larger values will reserve more RAM for python use and prevent the supervisor and SDK
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from large allocations of their own.
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Smaller values will likely grow sooner than large start sizes.
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CIRCUITPY_PYSTACK_SIZE
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~~~~~~~~~~~~~~~~~~~~~~
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Sets the size of the python stack. Must be a multiple of 4. The default value is currently 1536.
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Increasing the stack reduces the size of the heap available to python code.
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Used to avoid "Pystack exhausted" errors when the code can't be reworked to avoid it.
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CIRCUITPY_WEB_API_PASSWORD
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Password required to make modifications to the board from the Web Workflow.
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CIRCUITPY_WEB_API_PORT
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~~~~~~~~~~~~~~~~~~~~~~
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TCP port number used for the web HTTP API. Defaults to 80 when omitted.
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CIRCUITPY_WEB_INSTANCE_NAME
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Name the board advertises as for the WEB workflow. Defaults to human readable board name if omitted.
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CIRCUITPY_WIFI_PASSWORD
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~~~~~~~~~~~~~~~~~~~~~~~
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Wi-Fi password used to auto connect to CIRCUITPY_WIFI_SSID.
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CIRCUITPY_WIFI_SSID
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~~~~~~~~~~~~~~~~~~~
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Wi-Fi SSID to auto-connect to even if user code is not running.
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Additional board specific keys
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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`MaTouch ESP32-S3 Parallel TFT with Touch 7“ <https://circuitpython.org/board/makerfabs_tft7/>`_
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CIRCUITPY_DISPLAY_WIDTH
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~~~~~~~~~~~~~~~~~~~~~~~
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Selects the correct screen resolution (1024x600 or 800x640) for the particular board variant.
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If the CIRCUITPY_DISPLAY_WIDTH parameter is set to a value of 1024 the display is initialized
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during power up at 1024x600 otherwise the display will be initialized at a resolution
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of 800x480.
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`Sunton ESP32-2432S028 <https://circuitpython.org/board/sunton_esp32_2432S028/>`_
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CIRCUITPY_DISPLAY_ROTATION
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Selects the correct screen rotation (0, 90, 180 or 270) for the particular board variant.
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If the CIRCUITPY_DISPLAY_ROTATION parameter is set the display will be initialized
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during power up with the selected rotation, otherwise the display will be initialized with
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a rotation of 0. Attempting to initialize the screen with a rotation other than 0,
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90, 180 or 270 is not supported and will result in an unexpected screen rotation.
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