Integer to Bit Converter

Map vector of integers to vector of bits

Library

Utility Blocks

Description

The Integer to Bit Converter block maps each integer (or fixed-point value) in the input vector to a group of bits in the output vector.

The block maps each integer value (or stored integer when you use a fixed point input) to a group of M bits, using the selection for the Output bit order to determine the most significant bit. The resulting output vector length is M times the input vector length.

When you set the Number of bits per integer parameter to M and Treat input values as to Unsigned, then the input values must be between 0 and 2M-1. When you set Number of bits per integer to M and Treat input values as to Signed, then the input values must be between –2M-1 and 2M-1-1. During simulation, the block performs a run-time check and issues an error if any input value is outside of the appropriate range. When the block generates code, it does not perform this run-time check.

This block is single-rate and single-channel. It accepts a length N column vector or a scalar-valued (N = 1) input signal and outputs a length N·M column vector.

The block can accept the data types int8, uint8, int16, uint16, int32, uint32, single, double, and fixed point.

Dialog Box

Number of bits per integer

The number of bits the block uses to represent each integer of the input. This parameter must be an integer between 1 and 32.

Treat input values as

Indicate if the integer value input ranges should be treated as signed or unsigned. The default setting is Unsigned.

Output bit order

Define whether the first bit of the output signal is the most significant bit (MSB) or the least significant bit (LSB). The default selection is MSB first.

Output data type

You can choose the following Output data type options:

  • Inherit via internal rule

  • Smallest integer

  • Same as input

  • double

  • single

  • uint8

  • uint16

  • uint32

The default selection for this parameter is Inherit via internal rule.

When the parameter is set to Inherit via internal rule, the block determines the output data type based on the input data type.

  • If the input signal is floating-point (either single or double), the output data type is the same as the input data type.

  • If the input data type is not floating-point, the output data type is determined as if the parameter is set to Smallest integer.

When the parameter is set to Smallest integer, the block selects the output data type based on settings used in the Hardware Implementation pane of the Configuration Parameters dialog box.

  • If you select ASIC/FPGA, the output data type is the ideal one-bit size; ufix1.

  • For all other selections, the output data type is an unsigned integer with the smallest available word length, as defined in the Hardware Implementation settings (e.g. uint8)

Examples

Fixed-Point Integer To Bit and Bit To Integer Conversion (Audio Scrambling and Descrambling Example)

Overview

This example illustrates how to use the Bit to Integer and Integer to Bit Converter blocks with fixed-point signals.

This example uses a simplified audio scrambler configuration and a 16-bit, fixed-point digital audio source, which is recorded speech. The left-side of the model represents the audio scrambler subsystem and the right-side represents the descrambler subsystem.

Opening the Model

You can open the modelopen the model by typing doc_audioscrambler at the MATLAB® command line.

Structure

In the audio scrambler subsystem, the Integer to Bit Converter block unpacks each 16-bit audio sample into a binary, 1-bit signal. The binary signal passes to a linear feedback shift register (LFSR) scrambler, which randomizes the bits in a controllable way, thereby scrambling the signal. The Communications System Toolbox™ Scrambler block is used in the LFSR implementation. From the LFSR, the scrambled audio bits pass to the Bit to Integer Converter block. This block packs the scrambled 1-bit samples into 16-bit audio samples. The audio samples pass to the Data Type Conversion block, which converts the integer-based audio samples back into fixed-point samples.

The fixed-point samples pass from the scrambler subsystem to a channel. The channel sends the samples to the descrambler subsystem. For illustrative purposes, this example uses a noiseless channel. In an actual system, a channel may introduce noise. Removing such noise requires a more sophisticated design.

In the audio descrambler subsystem, the Integer to Bit Converter block unpacks each 16-bit audio sample into a binary, 1-bit signal. The binary signal passes to a linear feedback shift register (LFSR) descrambler, which randomizes the bits in a controllable way, reversing the scrambling process. This LFSR descrambler implementation uses the Communications System Toolbox Descrambler block. From the LFSR, the descrambled audio bits pass to the Bit to Integer Converter block. This block packs the descrambled 1-bit samples into 16-bit audio samples. The audio samples pass to the Data Type Conversion block, which converts the integer-based audio samples back into fixed-point samples.

In Simulink, the sfix16_En15 data type represents a signed (s) fixed-point (fix) signal with word length 16 and fraction length 15. Therefore, this model represents audio signals using the sfix16_En15 data type, except when converting to and from 1-bit binary signals. All 1-bit signals are represented by ufix1, as seen at the output of the Integer to Bit Converter block. The audio source has a frame size (or number of samples per frame) of 1024. For more information on fixed-point signals, please refer to Fixed-Point Numbers in the Simulink documentation.

Running the Model

You must run the example before you can listen to any of the audio signals.

You can run the example by clicking Simulation > Run.

You can hear the audio signals by clicking the model's yellow, audio icons.

Converter Block Settings

In the audio scrambler and descrambler subsystems, the Integer to Bit Converter block settings are:

  • Number of bits per integer: 16

  • Treat input values as: Signed

  • Output bit order: MSB first

  • Output data type: Inherit via internal rule

In the audio scrambler and descrambler subsystems, the Bit to Integer Converter block settings are:

  • Number of bits per integer: 16

  • Input bit order: MSB first

  • After bit packing, treat resulting integer values as: Signed

  • Output data type: Inherit via internal rule

See Also

de2bi and dec2bin

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