Packet Output
Write binary data or a CAN message to a communication channel
Libraries:
Simulink Desktop Real-Time
Description
The Packet Output block connects to and write unformatted binary data to a port, file, or CAN device. After you add a Packet Output block to your model, double-click the block to set its parameters.
The driver must be one of:
Standard Devices > File
Standard Devices > Serial Port
Standard Devices > TCP Protocol
Standard Devices > UDP Protocol
Kvaser > CAN Device
PEAK-System > CAN Device
Vector > CAN Device
MathWorks > virtual CAN (requires Vehicle Network Toolbox™)
When you install a UDP device, enter port addresses in decimal format in the Standard Devices UDP Protocol dialog box.
Any serial output port can send data with sample rates up to 500 Hz. To enable a faster sample rate of up to 10 kHz for some output serial ports, click Install new board, select Standard Devices > Serial Port, and select Direct port access.
The block does not support this option with all types of serial output hardware.
Examples
Packet Input/Output
Transfer data through UDP communication protocol using binary encoding.
CAN Input/Output with Vehicle Network Toolbox
Transfer data through CAN bus by using the CAN Pack and CAN Unpack blocks available in Vehicle Network Toolbox block library.
Ports
Input
Input Data — Data to write to communication channel
vector
Data values that are sent to communication channel as unformatted binary data. For CAN or Virtual CAN devices, this port supports:
CAN_MESSAGE
datatypeCAN_MESSAGE_BUS
datatypeCAN_FD_MESSAGE_BUS
datatype in CAN FD mode
Data Types: single
| double
| int8
| uint8
| int16
| uint16
| int32
| uint32
Output
Data Ready — Data ready port (optional)
1
| 0
This port signals 1
if the block is ready
to accept new data and 0
otherwise.
Dependency
When you select Show “Data Ready” port, this port is visible.
Data Error — Data error port (optional)
1
| 0
This port signals 1
if a data error occurs
and 0
otherwise.
Dependency
When you select Show “Data Error” port, this port is visible.
Missed Ticks — Missed tick count (optional)
double
In Connected IO mode, returns the number of timer ticks that your model lags behind the real-time kernel. When the model lags by more than Maximum missed ticks, the software reports an error and simulation stops.
Dependency
When you select Show “Missed Ticks” port, this port is visible.
Data Types: double
Parameters
Install new board — Register a board
< no board selected >
(default)
When you click Install new board, the software displays a list of manufacturers of supported boards. When you select a manufacturer, the software displays a list of boards available from that manufacturer. When you select a board, the software adds the board to the list of registered boards and makes that board the current board.
By default, the initial selection in the list of registered boards is <
no board selected >
.
For more information about driver support for I/O boards, see Hardware Support from Simulink Desktop Real-Time.
Dependency
When you select a board in the list of registered boards, the Delete current board and Board setup buttons are available.
Programmatic Use
Block Parameter:
DrvName |
Delete current board — Delete the current board
(button)
To delete the current board, click this button. The initial
selection of the list of registered boards changes to <
no board selected >
.
Dependency
To activate this parameter, select a board in the list of registered boards.
When you delete the current board, the Delete current board and Board setup buttons are no longer available.
Programmatic Use
Block Parameter:
DrvName |
Board setup — Set up the board
(button)
To set up the board, click this button.
A board-specific dialog box opens to set up the board. For more information, see the board manufacturer documentation.
Dependency
To activate this parameter, select a board in the list of registered boards.
To deactivate this parameter, click Delete current board.
Programmatic Use
Block Parameter:
DrvAddress |
Block Parameter:
DrvOptions |
Sample time — Sample time of block
0.1
(default) | double
Enter a value, in seconds, that represents how frequently you want the block to execute and interact with the I/O hardware. The block synchronizes your model with the real-time clock at this sample rate.
If you are using a fixed-step solver, enter the value that you entered as the Fixed step size configuration parameter or an integer multiple of that value.
Programmatic Use
Block Parameter:
SampleTime |
Maximum missed ticks — Number of timer ticks by which your model can trail the kernel
10
(default) | integer
In Connected IO mode, enter the number of timer ticks that your model can lag behind the real-time kernel. When the model lags behind by this number or fewer timer ticks, the software assumes that the lag is temporary. It allows the model to catch up, even if the model misses some ticks. When the model lags by more than this number, the software reports an error and simulation stops.
In Run in Kernel mode, the software ignores this value.
Programmatic Use
Block
Parameter:
MaxMissedTicks |
Show “Missed Ticks” port — Send number of missed ticks to port Missed Ticks
'off'
(default) | 'on'
In Connected IO mode, select this check box to send the number of missed
ticks to output port Missed Ticks
.
In Run in Kernel mode, the Missed Ticks
port is
zero.
Programmatic Use
Block Parameter:
ShowMissedTicks |
Yield CPU when waiting — Yield CPU while kernel waits for hardware
'off'
(default) | 'on'
In Connected IO mode, select this check box to grant other programs more CPU time while the kernel waits for a response from the hardware.
In Run in Kernel mode, the software ignores this value.
Programmatic Use
Block Parameter:
YieldWhenWaiting |
Packet identifier — Identifier of the packet
1
(default) | vector
Enter the ID of the packet to process. If your protocol does not have packet IDs, this parameter is disabled.
Programmatic Use
Block Parameter:
PacketID |
Extended identifier — Extended identifier of the packet (CAN boards only)
'off'
(default) | 'on'
Select this check box if Packet identifier is an extended identifier.
Programmatic Use
Block Parameter:
PacketID |
Output packet size — Number of bytes that each input packet contains
32
(default) | integer
Enter the number of bytes expected in each input packet. This number must match the number of bytes required by the type specifications in Output packet data types.
Programmatic Use
Block Parameter:
PacketSize |
Output packet field data types — Output type and grouping of data in the packet sent to the device
'4*double'
(default) | character vector | cell array of character vector
One or more character vectors that specify how data provided by the application is formatted into a packet. The Packet Output block has an input port corresponding to each character vector in Output packet field data types. Changing the number of character vectors changes the number of ports.
Each character vector has the format
[n*
]datatype
.
The data that the character vector describes has the type specified by
datatype
and the width specified by
n
. If n
is not
specified, the width is 1
. For example, 'double'
means one
double
value, and '4*int8'
means a vector of four
int8
values. You can also type 'CAN_MESSAGE'
to specify
a single CAN_MESSAGE
value.
The signal input to each port of the Packet Output block can be a scalar or vector of the data type. The character vector for each port specifies the type to be used when its signal is output to the device. If the character vector for a port matches the type of the signal input to that port, the signal value appears verbatim in the output packet.
You can also perform type conversion on output. For example,
assume that the input is a four-element int16
vector
and the character vector is '4*int8'
. The four
integers are converted to int8
before being written
to the packet. The resulting data occupies 4 bytes in the output packet.
The block forces an out-of-range value to the maximum value for that data type.
Programmatic Use
Block Parameter:
DataTypes |
Output packet field byte order — Byte order of packet being sent to device
Little Endian
(default) | Big Endian
From the list, select:
Little Endian
(default) — Receive multibyte values in little-endian format.Big Endian
— Receive multibyte values in big-endian format.
Programmatic Use
Block Parameter:
ByteOrder |
Show “Data Ready” port — Add port Data Ready
that signals 1
when the block can accept new data
'off'
(default) | 'on'
When you select this check box, the block makes visible the
output port Data Ready
. This output port signals 1
when
the block is ready to accept new data and otherwise signals 0
.
Programmatic Use
Block Parameter:
ShowReady |
Show “Data Error” port — Add port Data Error
that signals 1
if error occurs
'off'
(default) | 'on'
When you select this check box, the block makes visible the
output port Data Error
. This port signals 1
when
a data error occurs and 0
otherwise.
Programmatic Use
Block Parameter:
ShowError |
Initial value — Data to send when simulation begins
vector
Optional. Enter a vector that has the same number of elements as the sum of the widths of the input signals across all ports. When simulation begins, send the specified data before the other data that is sent during simulation.
Programmatic Use
Block Parameter:
InitialValue |
Final value — Data to send when simulation ends
vector
Optional. Enter a vector that has the same number of elements as the sum of the widths of the input signals across all ports. When simulation ends, after the other data that is sent during simulation, send the specified data.
Programmatic Use
Block Parameter:
FinalValue |
Version History
Introduced in R2007bR2024b: Update to blocks with port names
In R2024b, when you enable optional ports, such as Show "Missed Ticks" port, these Simulink® Desktop Real-Time™ block ports appear with labels.
R2020b: CAN and CAN FD Message Bus Datatypes
For CAN or Virtual CAN devices, the Packet Input block and
Packet Output block provide support for the
CAN_MESSAGE_BUS
datatype in CAN mode and support for the
CAN_FD_MESSAGE_BUS
datatype in CAN FD mode.
R2019b: Packet Input and Packet Output Blocks Support PEAK-System and Kvaser CAN Devices
The Packet Input block and Packet Output block support PEAK-System and Kvaser CAN devices.
R2019a: RS-232 Serial Port Drivers Support for macOS
The serial port drivers for the Packet Input block, Packet Output block, Stream Input block, and Stream Output block support macOS systems. In previous releases, the serial port drivers for these blocks supported Windows® systems only.
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