.. _usbc_device_stack:

USB-C device stack
##################

The USB-C device stack is a hardware independent interface between a
Type-C Port Controller (TCPC) and customer applications. It is a port of
the Google ChromeOS Type-C Port Manager (TCPM) stack.
It provides the following functionalities:

* Uses the APIs provided by the Type-C Port Controller drivers to interact with
  the Type-C Port Controller.
* Provides a programming interface that's used by a customer applications.
  The APIs is described in
  :zephyr_file:`include/zephyr/usb_c/usbc.h`

Currently the device stack only support implementation of Sink devices.

:ref:`List<usbc-samples>` of samples for different purposes.

Implementing a Sink Type-C and Power Delivery USB-C device
**********************************************************

The configuration of a USB-C Device is done in the stack layer and devicetree.

The following devicetree, structures and callbacks need to be defined:

* Devicetree usb-c-connector node referencing a TCPC
* Devicetree vbus node referencing a VBUS measurment device
* User defined structure that encapsulates application specific data
* Policy callbacks

For example, for the Sample USB-C Sink application:

Each Physical Type-C port is represented in the devicetree by a usb-c-connector
compatible node:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/boards/b_g474e_dpow1.overlay
   :language: dts
   :start-after: usbc.rst usbc-port start
   :end-before: usbc.rst usbc-port end
   :linenos:

VBUS is measured by a device that's referenced in the devicetree by a
usb-c-vbus-adc compatible node:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/boards/b_g474e_dpow1.overlay
   :language: dts
   :start-after: usbc.rst vbus-voltage-divider-adc start
   :end-before: usbc.rst vbus-voltage-divider-adc end
   :linenos:


A user defined structure is defined and later registered with the subsystem and can
be accessed from callback through an API:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst port data object start
   :end-before: usbc.rst port data object end
   :linenos:

These callbacks are used by the subsystem to set or get application specific data:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst callbacks start
   :end-before: usbc.rst callbacks end
   :linenos:

This callback is used by the subsystem to query if a certain action can be taken:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst check start
   :end-before: usbc.rst check end
   :linenos:

This callback is used by the subsystem to notify the application of an event:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst notify start
   :end-before: usbc.rst notify end
   :linenos:

Registering the callbacks:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst register start
   :end-before: usbc.rst register end
   :linenos:

Register the user defined structure:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst user data start
   :end-before: usbc.rst user data end
   :linenos:

Start the USB-C subsystem:

.. literalinclude:: ../../../samples/subsys/usb_c/sink/src/main.c
   :language: c
   :start-after: usbc.rst usbc start
   :end-before: usbc.rst usbc end
   :linenos:

API reference
*************

.. doxygengroup:: _usbc_device_api