Overview

FIR filter

Discussion

The FIR Module implements a direct convolution N-order Finite Impulse Response filter. The module operates on multiple channels with all channels sharing the same set of filter coefficients. The filter coefficients are stored in the array, coeffs, in normal order. The size of the array is numTaps x 1. The state variable array is of size numTaps*numChannels.

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On the processors of 2159x where 2 FIR accelerators are available with dual SHARC+ cores, two FIR accelerators are used which further reduces the processing load of multiple channels. Here the max FIRA channels = min(numChannels, 32*2). Please note that this module is not multi-core safe i.e. same module can not be used in Sharc1 and Sharc2 at the same time.

Type Definition

typedef struct _ModuleFIR
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 numTaps;                                // Length of the filter.
    INT32 stateIndex;                             // Index of the oldest state variable in the array of state variables.
    FLOAT32* coeffs;                              // Filter coefficient array in normal order.
    FLOAT32* state;                               // State variable array. The size of the array equals stateLen * numChannels.
    void * hardware_specific_struct_pointer;      // This is the internal TCB array used for ADI FIR accelerator
} ModuleFIRClass;
Variables

Variables

Properties

Pins

Input Pins

Name: in

Description: audio input

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Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out

Description: audio output

Data type: float

MATLAB Usage

File Name: fir_module.m

 M=fir_module(NAME, L)
 Creates an FIR filter object for use in the Audio Weaver environment.
 The module has a single multichannel input pin.
 
 Arguments:
    NAME - name of the module.
    L - length of the filter (number of taps).

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