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README.md

Zephyr-RTOS middleware port

This USB device MAC port builds on top of the Zephyr UDC drivers. Additionally, this port also implements HID over GATT service for BLE (see bluetooth subdirectory). The library can be integrated in two ways into a zephyr application:

  1. as a subdirectory / submodule of the application (guide below)
  2. as a zephyr module (example usage here)

1. Project setup

These are the list of changes to your app's CMakeLists.txt to get the library compiled into your project:

# C headers compiled with C++ give pointer conversion errors, turn them to warnings
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fpermissive")

# TODO set the relative path of c2usb project
set(C2USB_PATH "c2usb")

add_subdirectory(${C2USB_PATH})

# link the application to c2usb
target_link_libraries(app PRIVATE
    c2usb
)

In addition, include the library's Kconfig from your application's root Kconfig (assuming c2usb subpath):

rsource "c2usb/c2usb/port/zephyr/Kconfig"

2. Configuration

The following are required Zephyr Kconfig options:

CONFIG_C2USB_UDC_MAC=y

# RAM optimization:
# the buffer pool size can be cut down, as it's only used for control transfers
# CONFIG_UDC_BUF_POOL_SIZE=optimize based on your application (and check asserts)
# CONFIG_UDC_BUF_COUNT=3 + maximal used endpoint count in a configuration

# to enable HID over GATT support:
# CONFIG_C2USB_BLUETOOTH

3. Integrate the MAC

A usb::zephyr::udc_mac subclass object will be the glue that connects the Zephyr OS to this library. Create this object and pass it the devicetree object that represents the USB device, e.g.

usb::zephyr::udc_mac mac {DEVICE_DT_GET(DT_NODELABEL(zephyr_udc0))};

4. Your turn

If your porting journey took any unexpected steps, do let us know so we can share this knowledge with others.