View source for Signal Data Types

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This tutorial describes the data types which can be used to represent signals.

The starting flowgraph from [[Your_First_Flowgraph|Your First Flowgraph]] is used in this section, please complete the tutorial before proceeding. The next tutorial, [[Converting_Data_Types|Converting Data Types]], shows how to convert between different data types.

==Data Types==

Every input and output port on a block will have a data type associated with it. The data type is identified by the color of the input and output port. The GNU Radio data types can be found by opening GNU Radio Companion (GRC) and clicking ''Help: Types'':

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

A window displays the data types and their associated colors:

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

These colors correspond to the ''input and output ports'' for blocks in GRC.

The most common data types in GNU Radio blocks are ''Complex Float 32'' in '''<span style="color:blue">blue</span>''' and ''Float 32'' in '''<span style="color:orange">orange</span>'''. Additional colors include the ''Integer 16'' (or ''short'') data type in '''<span style="color:gold">yellow</span>''' and the ''Integer 8'' (or ''char'') data type in '''<span style="color:purple">purple</span>'''.

[[File:ExamplePortColors.png]]

==Complex Data Type==

The following flowgraph uses the ''Complex Float 32'' data type, which uses a pair of 32-bit floats to represent the real and imaginary portions of a complex sample.

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


Running the flowgraph shows the complex signal plotted in the time domain, where ''Signal 1'' is the real component and ''Signal 2'' is the imaginary component of the complex signal:

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

Each complex sample is therefore 64 bits: a 32-bit float for the real component, and a 32-bit float for the imaginary component.

==Float Data Type==

Many GNU Radio blocks support multiple data types. The data type of the ''Signal Source'' block can be changed by double-clicking it and selecting from the ''Output Type'' drop-down menu:

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

Selecting the ''float'' data type will have the ''Signal Source'' block create a real sinusoid, represented by the '''<span style="color:orange">orange</span>''' output port. Note the arrow connecting ''Signal Source'' to ''Throttle'' is '''<span style="color:red">red</span>''', indicating a data type mismatch error:

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


The error is resolved by converting all of the other blocks to the '''<span style="color:orange">orange</span>''' ''Float'' data type. Clicking on the block selects it, highlighting it in '''<span style="color:aqua">light blue</span>'''. Data types may be changed by pressing ''UP'' or ''DOWN'' on the keyboard:

[[File:BlockSelected.png|300px]]


The flowgraph is complete after all data types have been converted to ''Float'':

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


The ''Signal Source'' block creates a real output, which is displayed as the only signal in the time domain:

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


The next tutorial, [[Converting_Data_Types|Converting Data Types]], shows how to convert between different data types.  Eventually we will learn about vector streams, as part of the [[Streams and Vectors]] tutorial.