read

Read next VITA 49 packet

Since R2022b

Syntax

[signalDataPacket,contextPacket,contextPacketChangeIndex] = read(vita49ReaderObj)

[signalDataPacket,contextPacket,contextPacketChangeIndex,commandPacket,processedLength] = read(vita49ReaderObj,data)

[___] = read(vita49ReaderObj,Name=Value)

Description

[signalDataPacket,contextPacket,contextPacketChangeIndex] = read(vita49ReaderObj) reads the next packet from the VMEbus International Trade Association (VITA) 49 file specified by the input VITA 49 file reader object, vita49ReaderObj, and returns the signal data packet, signalDataPacket, and context packet, contextPacket. The function also returns the starting indices of the signal data packets after any new context packet arrival, in contextPacketChangeIndex. Note that the read function will terminate if it finds any ill-formatted packet while reading the file.

[signalDataPacket,contextPacket,contextPacketChangeIndex,commandPacket,processedLength] = read(vita49ReaderObj,data) reads the next packet form the VITA 49 data specified by data variable in the VITA 49 file reader object, vita49ReaderObj. The function also returns the number of decoded bytes processedLength from the given VITA 49 data.

[___] = read(vita49ReaderObj,Name=Value) specifies one or more optional name-value arguments, in addition to the output arguments from the previous syntax. For example, StreamID=2 sets the stream identifier to 2.

Examples

Read Specified Number of Packets from File

Create a VITA 49 file reader object, specifying the name of a VITA 49 file and an output format for the packet timestamp.

vita49ReaderObj = vita49Reader("VITA49SampleData.bin");
vita49ReaderObj.OutputTimestampFormat = "seconds";

Specify the number of packets to be read from the file.

numpkt = 11;

Read the specified number of packets from the VITA 49 file to the MATLAB® workspace.

[signalDataPacket,contextPacket,contextPacketChangeIndex] = read(vita49ReaderObj,NumPackets=numpkt)

signalDataPacket = struct with fields:
                  PacketType: 1
                    StreamID: 0
                     ClassID: "7C386C0000"
                 PadBitCount: 0
        IntegerTimestampType: "GPS"
       IntegerTimestampValue: 1625215654
     FractionalTimestampType: "real time"
    FractionalTimestampValue: 900000344000
                    RawBytes: [1472x1 uint8]
                   IQSamples: [722x1 double]
                     Trailer: [1x1 struct]

contextPacket=1×10 struct array with fields:
    PacketType
    StreamID
    ClassID
    IntegerTimestampType
    IntegerTimestampValue
    FractionalTimestampType
    FractionalTimestampValue
    RawBytes
    ContextFieldChangeIndicator
    ReferencePointIdentifier
    Bandwidth
    IFReferenceFrequency
    RFFrequency
    RFFrequencyOffset
    IFBandOffset
    ReferenceLevel
    Gain
    OverRangeCount
    SampleRate
    TimestampAdjustment
    TimestampCalibrationTime
    StateAndEventIndicator
    SignalDataPayloadFormat
      ⋮

contextPacketChangeIndex = 1×10

     0     0     0     0     0     0     0     0     0     1

Clear the vita49Reader System object.

clear vita49ReaderObj

Read Packets in Streaming Mode from File

Create a VITA 49 file reader object, specifying the name of a VITA 49 file.

vita49ReaderObj = vita49Reader("VITA49SampleData.bin");

Set the stream identifier as 1, class identifier as "736C860000", and packet type as signal data packet.

pktType = "signal data";
streamID = 0;
classID = "7C386C0000";

In streaming mode, read the VITA 49 packets that match the specified filters to the MATLAB workspace.

for idx = 1:3
    signalDataPacket = read(vita49ReaderObj, ...
      PacketType=pktType,StreamID=streamID,ClassID=classID)
end

signalDataPacket = struct with fields:
                  PacketType: 1
                    StreamID: 0
                     ClassID: "7C386C0000"
                 PadBitCount: 0
        IntegerTimestampType: "GPS"
       IntegerTimestampValue: 1625215654
     FractionalTimestampType: "real time"
    FractionalTimestampValue: 900000344000
                    RawBytes: [1472x1 uint8]
                   IQSamples: [722x1 double]
                     Trailer: [1x1 struct]

signalDataPacket = struct with fields:
                  PacketType: 1
                    StreamID: 0
                     ClassID: "7C386C0000"
                 PadBitCount: 0
        IntegerTimestampType: "GPS"
       IntegerTimestampValue: 1625215654
     FractionalTimestampType: "real time"
    FractionalTimestampValue: 900042328000
                    RawBytes: [1472x1 uint8]
                   IQSamples: [722x1 double]
                     Trailer: [1x1 struct]

signalDataPacket = struct with fields:
                  PacketType: 1
                    StreamID: 0
                     ClassID: "7C386C0000"
                 PadBitCount: 0
        IntegerTimestampType: "GPS"
       IntegerTimestampValue: 1625215654
     FractionalTimestampType: "real time"
    FractionalTimestampValue: 900084248000
                    RawBytes: [1472x1 uint8]
                   IQSamples: [722x1 double]
                     Trailer: [1x1 struct]

Clear the vita49Reader System object.

clear vita49ReaderObj

Read Specified Number of Packets from Workspace

Create a VITA 49 file reader object without any input arguments.

vita49ReaderObj = vita49Reader;

Load vita49Data.mat into the workspace.

load('vita49Data.mat')

The vita49Data.mat consists of a variable data with 37 VITA 49 packets. Read the VITA 49 packets from the variable data.

[sigDataPackets,contextPackets,contextChangeIdx,commandPackets, ...
      processedlen] = read(vita49ReaderObj, data, "NumPackets",37);

Clear the vita49Reader System object.

clear vita49ReaderObj

Input Arguments

vita49ReaderObj — VITA 49 file reader

vita49Reader object

VITA 49 file reader, specified as a vita49Reader object.

data — VITA 49 formatted data

array

VITA 49 formatted data, specified as a unit8 array in the workspace.

Data Types: uint8

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: StreamID=2 sets the stream identifier to 2.

PacketType — Type of packet to be read

"signal data" | "context" | "command"

Type of packet to be read, specified as "signal data", "context", or "command". If you do not specify this argument, the function reads the next packet from the file.

Data Types: char | string

NumPackets — Number of packets to be read

1 (default) | positive integer

Number of packets to be read, specified as a positive integer. To read all packets up to the end of the file, set NumPackets to intmax ("uint32") or intmax ("uint64").

Data Types: double | uint32 | uint64

StreamID — Stream identifier

nonnegative integer

Stream identifier, specified as a nonnegative integer.

If you specify StreamID, the function identifies the packets belonging to only the specified ID from the packet stream.

Data Types: uint32

ClassID — Class identifier

character vector | string scalar

Class identifier, specified as a character vector or string scalar.

A class identifier is a 5-byte-long, hex-formatted string that includes three bytes of Organizational Unique Identifier (OUI) information and two bytes of information class code.

Data Types: char | string

Output Arguments

signalDataPacket — Decoded signal data packet

structure

Decoded signal data packet, returned as a structure. For more information about this output, see Signal Data Packet.

Data Types: struct

contextPacket — Decoded context packet

structure

Decoded context packet, returned as a structure. For more information about this output, see Context Packet.

Data Types: struct

contextPacketChangeIndex — Starting indices of signal data packets after any new context packet arrival

array of nonnegative integers

Starting indices of the signal data packets after any new context packet arrival, returned as an array of nonnegative integers.

When two context packets arrive one after another, the corresponding value returned is two zeros.

Data Types: double

commandPacket — Undecoded command packet

structure

Undecoded command packet, returned as a structure. For more information about this output, see Command Packet.

Data Types: struct

processedLength — Number of bytes processed

nonnegative integer

Number of bytes processed in a read call, returned as a nonnegative integer.

Data Types: double

Extended Capabilities

C/C++ Code Generation

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

Usage notes and limitations:

Code generation is available only when the OutputTimestampFormat property of the vita49Reader object is set to the default value of "seconds".

Version History

Introduced in R2022b