.. _feedback_messages:

Feedback Messages
=================

There are currently three streaming feedback messages available:

- Streaming Status
- Cartesian Pose
- Joint Pose

For further information on getting started with feedback messages, refer to :ref:`Getting Started: Streaming Feedback <streaming_feedback>`.
Additionally, there is also an :ref:`example receiver <example_receiver>` provided.


.. note::
   
   Floating point numbers are encoded in network byte order (i.e. "Big Endian").
   Please note the 
   `python documentation <https://docs.python.org/3/library/struct.html#byte-order-size-and-alignment>`_ 
   for further instructions on unpacking.
   

The figure below shows the message format. 

.. figure:: /_static/streaming_messages/feedback_messages.drawio.svg
    :align: center


Streaming Feedback Message Header
---------------------------------

All streaming feedback messages share the same header. This header contains:

- Streaming State (uint8): Feedback on the current state of the streaming mode
    - inactive (0x00): Streaming not active
    - ready (0x10): Streaming enabled, currently not following streamed trajectory
    - streaming (0x20): following streamed trajectory
- Message ID (uint8): Identifies the type of feedback message, i.e. the format and content of the payload
    - status (0x00)
    - cartesian pose (0x01)
    - joint pose (0x02)

Streaming Feedback Message Payload
----------------------------------

Besides the header, the payload of the message depends on its type:

- Streaming Status (0x00) --> Payload Size: 1 Byte
    - Buffer Size (uint8): current number of buffered poses
- Cartesian Pose (0x01) --> Payload Size: 28 Bytes
    - translation (3 x float): x, y and z coordinate of the TCP relative to the base in [m]
    - orientation (4 x float): W, X, Y and Z quaternion component of the TCP relative to the base in [-]
- Joint Pose (0x02) --> Payload Size: n x 4 Bytes
    - joint angles (n x float): joint angle for each joint in [rad]