Environment Variables ===================== CircuitPython 8.0.0 introduces support for environment variables. Environment variables are commonly used to store "secrets" such as Wi-Fi passwords and API keys. This method *does not* make them secure. It only separates them from the code. CircuitPython supports these by mimicking the `dotenv `_ CPython library. Other languages such as Javascript, PHP and Ruby also have dotenv libraries. These libraries store environment variables in a ``.env`` file. Here is a simple example: .. code-block:: bash KEY1='value1' # Comment KEY2='value2 is multiple lines' CircuitPython uses the ``.env`` at the drive root (no folder) as the environment. User code can access the values from the file using `os.getenv()`. It is recommended to save any values used repeatedly in a variable because `os.getenv()` will parse the ``/.env`` on every access. CircuitPython behavior ---------------------- CircuitPython will also read the environment to configure its behavior. Other keys are ignored by CircuitPython. Here are the keys it uses: CIRCUITPY_BLE_NAME ~~~~~~~~~~~~~~~~~~ Default BLE name the board advertises as, including for the BLE workflow. CIRCUITPY_RESERVED_PSRAM ~~~~~~~~~~~~~~~~~~~~~~~~ On boards with Espressif microcontrollers with PSRAM (also called SPIRAM), permanently reserve a portion of PSRAM for use by esp-idf. This storage is removed from the CircuitPython "heap" and is available for allocation by esp-idf routines in the core instead. Generally, only set this to a non-zero value when it is required by a specific core module. CIRCUITPY_WEB_API_PASSWORD ~~~~~~~~~~~~~~~~~~~~~~~~~~ Password required to make modifications to the board from the Web Workflow. CIRCUITPY_WEB_API_PORT ~~~~~~~~~~~~~~~~~~~~~~ TCP port number used for the web HTTP API. Defaults to 80 when omitted. CIRCUITPY_WIFI_PASSWORD ~~~~~~~~~~~~~~~~~~~~~~~ Wi-Fi password used to auto connect to CIRCUITPY_WIFI_SSID. CIRCUITPY_WIFI_SSID ~~~~~~~~~~~~~~~~~~~ Wi-Fi SSID to auto-connect to even if user code is not running.