Writing Transmission Formatting Python Scripts
#########################################################

The transmission message may be modified using Python scripts.
This tutorial will show you how.

You do not need to have the full Python development environment setup for this.
`LinkComm  <|link_linkcomm_for_win|>`_
will suffice.


The manual has crucial information about how scripts work.
    |link_satlink_manual|

Please take the time to read the chapter on Python scripts.
Without that knowledge, it is going to be difficult to work with |short_port_name| scripts.

Appending Data to Transmissions
*******************************************

In this example, we want to append a specific data string to the transmission message.

Suppose that the system currently uses CSV formatting to transmit data, making the transmission
message look like this:

::

    04/02/2018,09:00:00,STAGE,20.501
    04/02/2018,09:00:00,TEMP,23.5


Our goal is to append the following fixed string to the message:

::

    Little Creek A21938

Such that the final message is

::

    04/02/2018,09:00:00,STAGE,20.501
    04/02/2018,09:00:00,TEMP,23.5
    Little Creek A21938

------------

These are the steps that the station will take:

- The system will create a standard transmission message based on the setup
- The Python script will be invoked
- The standard message will be provided to the script
- The script will modify the message
- The script will return the modified message to the system
- The system will transmit the modified message

------------

Python code would look like this:

.. code-block:: python

    @TXFORMAT
    def append_info(standard):
       return standard + "Little Creek A21938"


- Note that all transmission formatting scripts must have the @TXFORMAT descriptor.


Here is the completed Python script:

    :download:`append_info.py<./setup_script/append_info.py>`

------------

Now that we have the script, we need to integrate it into the setup using LinkComm.

* Run LinkComm

------------

    |LinkCommSL3Connect|

* Choose Station Type XLink 500
* Click Work offline.

------------

    |LinkCommOpenScript|

* Go to the Script tab of LinkComm and open the append_info script file.

------------

    |LinkCommTxFormat|

* Go to the Telemetry tab of LinkComm.
* Setup the Transmission format:
* Set Tx Format CSV
* Check Custom Script Format
* Choose append_info as the Script Format Function

Completed setup file:
    - :download:`append info<./setup_script/append_info_setup.txt>`


That completes this example.  For more example scripts,
please see

    - :doc:`examples/txformat_simple`

    - :doc:`examples/dga`

    - :doc:`examples/log_txformat`

    - :doc:`examples/NFDRS_TX_Format`





.. |LinkCommSL3Connect| image:: ./media/image30.png
   :width: 5.00000in
   :height: 3.70000in
.. |LinkCommOpenScript| image:: ./media/image47.png
   :width: 6.00000in
   :height: 4.50000in
.. |LinkCommTxFormat| image:: ./media/image48.png
   :width: 6.00000in
   :height: 4.50000in