.. _gettingStartedFIRDoc:

.. index:: single: Example; FIR Filter and Module

=====================
FIR Filter and Module
=====================

::

	constant Coefficients [4] {
		value:	[ 0.25, 0.25, 0.25, 0.25 ]
		meta:	'Coefficients of FIR filter'
	}

	signal Taps [4] {
		default:	0.0
		rate:		AudioRate
		reset:		MasterReset
		meta:		'Taps holds a single sample Delayed value'
	}

	AudioIn [1]
	>> FixedDelay (
		samples:	[ 0, 1, 2, 3 ]
		default: 	0.0
		reset:		off
		bypass:		off
	)
	>> Taps;

	Taps * Coefficients
	>> Mix ()
	>> AudioOut [1:2];
	
::

	AudioIn[1] >> FixedDelay ( samples: 0 ) >> Taps[1];
	AudioIn[1] >> FixedDelay ( samples: 1 ) >> Taps[2];
	AudioIn[1] >> FixedDelay ( samples: 2 ) >> Taps[3];
	AudioIn[1] >> FixedDelay ( samples: 3 ) >> Taps[4];
	
::

	signal Intermediate [4] {
		default:	0.0
		rate:		AudioRate
		reset:		MasterReset
		meta:		'Holds intermediate values of Taps * Coefs'
	}

	signal Sum {
		default:	0.0
		rate:		AudioRate
		reset:		MasterReset
		meta:		'Holds Sum of Taps * Coefs'
	}

	Taps[1] * Coefficients[1] >> Intermediate[1];
	Taps[2] * Coefficients[2] >> Intermediate[2];
	Taps[3] * Coefficients[3] >> Intermediate[3];
	Taps[4] * Coefficients[4] >> Intermediate[4];

	Intermediate[1] + Intermediate[2] + Intermediate[3] + Intermediate[4] >> Sum;

	Sum >> AudioOut[1:2];
	
::

	module FIR {
		input:			Input
		output:			Output
		propertyName:		[ 'length', 'coefficients', 'reset' ]
		propertyDirection:	in
		propertyBlock: 	[ 	
			constant Length { value: 2 }, 
			constant Coefficients [Length] { value: [ 0.5, 0.5 ] },
			trigger Reset {}
		]
		internalBlock:		[
			signal Input {
				default: 	0.0
				rate:		streamRate
				reset:		Reset
			},
			signal Output {
				default: 	0.0
				rate:		streamRate
				reset:		Reset
			},
			signal DelayValues [Length] { 
				default: 	0 
				rate:		none
				reset:		none
			},
			signal Taps [Length] { 
				default: 	0.0 
				rate:		none
				reset:		Reset
			} 
		]
		streams:		[
			Counter ( 
				startValue:	0
			)
			>> Table (
				size:	Length
				rate:	Length	
			)
			>> DelayValues;
			,
			Input
			>> FixedDelay (
				samples:	DelayValues
				default: 	0.0
				reset:		Reset
				bypass:		off
			)
			>> Taps;
			,
			Taps * Coefficients
			>> Mix ()
			>> Output;
		]
		meta:			'Generic Real FIR Filter'
	}

	constant FIR_Length {
		value:	8
		meta:	'Length of FIR Filter'
	}

	constant FIR_Coef [FIR_Length] {
		value: 	1.0 / FIR_Length
		meta:	'FIR Filter Coefficients'
	}

	AudioIn[1]
	>> FIR (
		length:		FIR_Length
		coefficients:	FIR_Coef
		reset:		off
	)
	>> AudioOut[1:2];