.. _gptp-support:

gPTP stack for Zephyr
#####################

Overview
********

This gPTP stack supports the protocol and procedures as defined in
the `IEEE 802.1AS-2011 standard`_ (Timing and Synchronization for
Time-Sensitive Applications in Bridged Local Area Networks).

Supported features
*******************

The stack handles communications and state machines defined in the
`IEEE 802.1AS-2011 standard`_. Mandatory requirements for a full-duplex
point-to-point link endpoint, as defined in Annex A of the standard,
are supported.

The stack is in principle capable of handling communications on multiple network
interfaces (also defined as "ports" in the standard) and thus act as
a 802.1AS bridge. However, this mode of operation has not been validated on
the Zephyr OS.

Supported hardware
******************

Although the stack itself is hardware independent, Ethernet frame timestamping
support must be enabled in ethernet drivers.

Boards supported:

- :ref:`frdm_k64f`
- :ref:`sam_e70_xplained`
- :ref:`native_posix` (only usable for simple testing, limited capabilities
  due to lack of hardware clock)
- :ref:`qemu_x86` (emulated, limited capabilities due to lack of hardware clock)

Enabling the stack
******************

The following configuration option must me enabled in :file:`prj.conf` file.

- :option:`CONFIG_NET_GPTP`

Application interfaces
**********************

Only two Application Interfaces as defined in section 9 of the standard
are available:

- ClockTargetPhaseDiscontinuity interface (:cpp:func:`gptp_register_phase_dis_cb()`)
- ClockTargetEventCapture interface  (:cpp:func:`gptp_event_capture()`)

Function prototypes can be found in :file:`include/net/gptp.h` and in the
:ref:`networking_api` documentation.

Testing
*******

The stack has been informally tested using the OpenAVB gPTP and
Linux ptp4l daemons. The :ref:`gptp-sample` sample application from the Zephyr
source distribution can be used for testing.

.. _IEEE 802.1AS-2011 standard:
   https://standards.ieee.org/findstds/standard/802.1AS-2011.html