doc: connectivity: usb: add initial CDC ACM documentation #96716
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Add initial documentation for CDC ACM function provided by the new USB device stack. Signed-off-by: Johann Fischer <[email protected]>
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Sep 30, 2025
| and a compatible node in the devicetree sources is present. If necessary, CDC ACM | ||
| support can be explicitly disabled by :kconfig:option:`CONFIG_USBD_CDC_ACM_CLASS`. | ||
| The number of possible CDC ACM instances depends on the number of supported | ||
| endpoints on the USB device controller. |
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Maybe add something like:
Each CDC ACM instance requires three endpoints: two bulk (one IN, one OUT) and one interrupt IN (with Max Packet Size = 16).
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| Since the use case as a serial backend is very common and no configuration is | ||
| necessary at runtime for the CDC ACM UART, the stack offers a helper that | ||
| performs the steps described in :ref:`usb_device_next_howto_configure`. The | ||
| helper is enabled by the :kconfig:option:`CONFIG_CDC_ACM_SERIAL_INITIALIZE_AT_BOOT` | ||
| and initializes the USB device stack with a single CDC ACM instance. Sample | ||
| :zephyr:code-sample:`usb-cdc-acm-console` demonstrates how to use it. | ||
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| :kconfig:option:`CONFIG_CDC_ACM_SERIAL_INITIALIZE_AT_BOOT` should also be used | ||
| by the boards like :zephyr:board:`nrf52840dongle`, which do not have a debug | ||
| adapter but a USB device controller, and wants to use CDC ACM UART as default | ||
| serial backend for logging and shell. | ||
| As the configuration would be identical for any board, there are common | ||
| :zephyr_file:`devicetree file <boards/common/usb/cdc_acm_serial.dtsi>` and | ||
| :zephyr_file:`Kconfig file <boards/common/usb/Kconfig.cdc_acm_serial.defconfig>` | ||
| that must be included in the board's devicetree and Kconfig.defconfig files. |
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Add initial documentation for CDC ACM function provided by the new USB device stack.