Byte Packing

Construct data frames

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Libraries:
Simulink Real-Time / Utilities

Description

The Byte Packing block converts one or more signals of user-selectable data types to a single vector of varying data types. The output of this block typically connects to an input port of a Send block.

The Byte Packing block and the Byte Unpacking block support the Simulink^® Real-Time™ STF code generation targets and generate code that runs on Speedgoat target machines. Due to considerations such as endianness and addressable word size, these blocks can generate incorrect results for other code generation targets or target computers.

For example, suppose that you are packing three signals into a vector of uint8. The signals have the following attributes:

Dimension	Size	Type
Scalar	1	single
Vector	3	uint8
Vector	3	uint8

1. Set the packed output port data type to uint8.

2. Set the input port data type to a cell array encoding the data types:

   {'single', ['uint8'], ['uint8']}

   Use square brackets to represent vectors.

3. Set the byte alignment value to 1.

4. Connect the signals to the Byte Packing block.

Examples

Simple ASCII Encoding/Decoding Loopback Test (with Baseboard Blocks)

Convert a single floating point number to ASCII and transmit the value over a serial link.

• Open Script

ASCII Encoding/Decoding Loopback Test

Send ASCII data over a serial link.

• Open Script

ASCII Encoding/Decoding Loopback Test (with Baseboard Blocks)

Send ASCII data over a serial link.

• Open Model

ASCII Encoding/Decoding Resync Loopback Test

Use the ability of the FIFO Read HDRS block to resynchronize after being repeatedly disabled and apply this ability to resolve errors such as when a message is only partially complete at the time the read is attempted.

• Open Script

ASCII Encoding/Decoding Resync Loopback Test (with Baseboard Blocks)

Use the ability of the FIFO Read HDRS block to resynchronize after being repeatedly disabled and apply this ability to resolve errors such as when a message is only partially complete at the time the read is attempted.

• Open Script

Binary Encoding/Decoding Loopback Test

Send Binary data over a serial link.

• Open Script

Binary Encoding/Decoding Loopback Test (with Baseboard Blocks)

Send Binary data over a serial link.

• Open Script

Binary Encoding/Decoding Resync Loopback Test

Use the ability of the FIFO Read BINARY block to handle messages that are interrupted and only partially complete.

• Open Script

Binary Encoding/Decoding Resync Loopback Test (with Baseboard Blocks)

Use the ability of the FIFO Read BINARY block to handle messages that are interrupted and only partially complete.

• Open Script

Ports

Input

Port_1 — First of N input ports

scalar | vector

The block has from 1 to N input ports. Specify the number of input ports and their types by entering them as a cell array in the parameter Input port (unpacked) data types (cell array).

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean

Output

Port_1 — Output port containing packed data

vector

The block displays one output port that transmits a vector of packed data. You determine the data type of the packed data by setting Output port (packed) data type.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean

Parameters

Output port (packed) data type — Data type for the packed output signal

uint8 (default) | double | single | int8 | int16 | uint16 | int32 | uint32 | boolean

From the list, select a data type for the output port.

Programmatic Use

Block Parameter: MaskPackedDataType

Input port (unpacked) data types (cell array) — Data types for the unpacked input signals

{'uint8'} (default) | double | single | int8 | int16 | uint16 | int32 | uint32 | boolean

Specify as a cell array the data types of the input ports (unpacked) for the different input signals. The number of elements in the cell array determines the number of input ports shown by this block instance. To represent vector elements, use square brackets in the cell array.

Programmatic Use

Block Parameter: MaskUnpackedDataTypes

Byte Alignment — Alignment of the input signal data types after packing

1 (default) | 2 | 4 | 8

Each element in the input signals list starts at a multiple of the alignment value, specified from the start of the vector. If the alignment value is larger than the size of the data type in bytes, the block fills the space with pad bytes of value 0.

For example, if the alignment value is 4:

• uint32 receives no padding

• uint16 receives 2 bytes of padding

• uint8 receives 3 bytes of padding

If the model accesses the data items frequently, consider selecting an alignment value equal to the largest data type that you want to access. If the model transfers data items frequently as a group, consider an alignment value of 1, which packs the data into as small a space as possible.

Programmatic Use

Block Parameter: MaskAlignment

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

The Byte Packing block supports C++ code generation only.

Version History

Introduced in R2006a