Creating Your First Block: Difference between revisions

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[[File:SelectFindAndReplace.png|700px]]
[[File:SelectFindAndReplace.png|700px]]


Enter ''example_param'' under ''Find'', and ''additionFlag'' under ''Replace with'':
 
Enter ''example_param'' under ''Find'', and ''additionFlag'' under ''Replace with'', and then click ''Replace All'':


[[File:FindReplaceExamplePara.png|500px]]
[[File:FindReplaceExamplePara.png|500px]]

Revision as of 18:41, 10 January 2022

This tutorial will guide you through creating your first block with the Embedded Python Block. The previous tutorial is here: Streams and Vectors

Opening Code Editor

The Embedded Python Block is a tool to quickly prototype a block within a flowgraph. Search for the Python Block and add it to the workspace:

AddPythonBlockToWorkspace.png


Double-click the box to edit the properties. The Embedded Python Block has two properties,

  1. Code, a click-box which contains a link to the Python code for the block and
  2. Example_Param, an input parameter to the block.


Click on Open in Editor to edit the Python code:

EmbeddedPythonBlockProperties.png


You will be prompted with another choice for which editor to use to write the Python code. Click Use Default:

ClickUseDefault.png


An editor window will then display the Python code for the Embedded Python Block:

PythonCodeGedit.png


Components of a Python Block

There are three important sections in the Python block code:

  1. import statements in green
  2. __init__ function in orange
  3. work function in red

PythonBlockCodeFunctions.png


The import statement includes the NumPy and GNU Radio libraries.

The __init__ statement:

  1. Accepts the example_param parameter with a default argument of 1.0
  2. Declares the block to have a np.complex64 input and output, which is the GNU Radio Complex Float 32 data type
  3. Stores the self.example_param variable from the input parameter

The work function:

  1. Has the input input_items and output output_items parameters
  2. Applies a mathematical operation to input_items and stores the result in output_items
  3. Returns the number of samples produced

The example block we are creating will either add or multiply the two blocks based on the input parameter example_param. In order to do this, the work function will need to be modified.

Editing Python Block Code

The pseudo code for the Python block is:

if (additionFlag is True)
    then add the two inputs
else
    then multiply the two inputs

The first step will be to rename example_param to additionFlag. From the editor menu select Find and Replace:

SelectFindAndReplace.png


Enter example_param under Find, and additionFlag under Replace with, and then click Replace All:

FindReplaceExamplePara.png