Hysteresis

Overview

Threshold with hysteresis

Discussion

The hysteresis module implements switching above and below a threshold. The module accepts floating-point inputs and outputs 0 when the signal level is below the threshold and 1 when above. Instead of just a single threshold the module incorporates hysteresis by having separate upper and lower thresholds. The output switches from 0->1 when the input signal rises above the upperThreshold and then stays at 1 until the signal drops below the lowerThreshold. The module is thus above to avoid frequent switching when signal levels are close to the threshold.

If you need just a straightforward comparison against a threshold without hysteresis, use the logic_compare_const_modulue.m.

The module accepts multichannel signals and outputs a separate Boolean value per channel. The module operates on a sample-by-sample basis and the block size of the output equals the block size of the input.

When bypassed, the module continues to process data normally. That is, the module's processing function is called even when it is bypassed.

Module Pack

Advanced

ClassID

classID = 1287

Type Definition

typedef struct _ModuleHysteresis
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
FLOAT32 upperThreshold;                       // Upper switching threshold
FLOAT32 lowerThreshold;                       // Lower switching threshold
INT32* state;                                 // Current state per chanel
} ModuleHysteresisClass;

Variables

Properties

Name	Type	Usage	Default Value	Range
upperThreshold	float	parameter	1	Unrestricted
lowerThreshold	float	parameter	-1	Unrestricted
state	int*	state	[1 x 1]	Unrestricted

Pins

Input Pins


Name	in
Description	Input signal
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	Output signal
Data Type	int

Matlab Usage

File Name: hysteresis_module.m 
 M = hysteresis_module(NAME) 
 This module implements Boolean selection above and below a threshold 
 and adds hysteresis to the design to avoid frequent switching. 
 Arguments: 
    NAME - name of the module.