Packet Input

Receive unformatted binary data


Real-Time Windows Target™


The Packet Input block receives unformatted binary data. After you add a Packet Input block to your model, double-click the block to set its parameters.

The driver must be Standard Devices > Serial Port, Standard Devices > UDP Protocol, Standard Devices > File, or Vector > CAN Device. When you install a UDP device, enter port addresses in decimal format in the Standard Devices UDP Protocol dialog box.


Sample time

Enter a value representing how frequently you want the block to execute and interact with the I/O hardware. The block also synchronizes your model with the real-time clock at this sample rate.

    Tip   If you are using a fixed-step solver, you must enter the same value that you entered in the Fixed step size box in the Configuration Parameters dialog box, or an integer multiple of that value.

Maximum missed ticks

Enter the number of timer ticks that your model can lag behind the real-time kernel. When the model lags by more than this number, the block reports an error and simulation stops. Otherwise, simulation continues even if some ticks are missed.

Show "Missed Ticks" port

Select this check box to display the current number of missed ticks as a block output.

Yield CPU when waiting

Select this check box to grant other programs more CPU time while the kernel waits for a response from the hardware.

Packet identifier

Enter the ID of the packet to receive. If your protocol does not have packet IDs, this parameter is disabled.

Extended identifier

Check this check box if Packet identifier is an extended identifier.

Input packet size

Enter the number of bytes expected in each input packet. This number must be the same as the number of bytes required by the type specifications in Block output data types.

Block output data types

Enter a string, or a cell array of strings, that specifies how the data in each packet obtained from the device is to be typed and grouped for input to the application. The Packet Input block has an output port corresponding to each string in Block output data types. Changing the number of strings automatically changes the number of output ports.

Each string has the format [n*]datatype. The data described by the string has the type specified by datatype and the width specified by n; or 1 if n is not specified. 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.

By providing a cell array of such strings, you can convert an input packet into the types required, packaged into vectors as required. For example, specifying {'int16','int16','double'} creates three ports. The first and second each output an int16 value, and the third outputs a double. Specifying {'2*int16','double'} creates two ports: a vector of two int16 values, and a scalar double.

    Note:   An out-of-range value is forced to the maximum value for that data type.

Input packet field byte order

From the list, select:

  • Little Endian

    Default. Send multibyte values in little-endian format.

  • Big Endian

    Send multibyte values in big-endian format.

Show "Data Ready" port

Select this check box to indicate that the block has an output port that signals 1 if the block has new data available, and 0 otherwise.

Show "Data Error" port

Select this check box to indicate that the block has an output port that signals 1 if a data error has occurred, and 0 otherwise.

Show packet timestamp port

Select this check box to show the time stamp for the CAN message packets. If your protocol does not have packet time stamps, the block ignores this value.

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