Hier Blocks and Parameters

This tutorial describes how to create a hierarchical block, or Hier block, in GRC. The previous tutorial, Creating Your First Block, demonstrates how to create your first GNU Radio block using the Embedded Python Block.

Creating a Flowgraph

A hier block is used to encapsulate and simplify multiple GNU Radio blocks into a single block. The example hier block will be a frequency shifter block which multiplies a Signal Source against an input signal.

The first step is creating the flowgraph. Drag and drop the following blocks into the workspace:

1. Signal Source
2. Multiply
3. Noise Source
4. Low Pass Filter
5. Throttle
6. QT GUI Frequency Sink
7. QT GUI Range

Connect the blocks:

Update the QT GUI Range properties:

• Id: frequency
• Default Value: 0
• Start: -samp_rate/2
• Stop: samp_rate/2