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binblockread

Read binblock data from instrument

Syntax

A = binblockread(obj)
A = binblockread(obj,'precision')
[A,count] = binblockread(...)
[A,count,msg] = binblockread(...)

Arguments

obj

An interface object.

'precision'

The number of bits read for each value, and the interpretation of the bits as character, integer, or floating-point values.

A

Binblock data returned from the instrument.

count

The number of values read.

msg

A message indicating if the read operation was unsuccessful.

Description

A = binblockread(obj) reads binary-block (binblock) data from the instrument connected to obj and returns the values to A. The binblock format is described in the binblockwrite reference pages.

A = binblockread(obj,'precision') reads binblock data translating the MATLAB® values to the precision specified by precision. By default the uchar precision is used and numeric values are returned in double-precision arrays. Refer to the fread function for a list of supported precisions.

[A,count] = binblockread(...) returns the number of values read to count.

[A,count,msg] = binblockread(...) returns a warning message to msg if the read operation did not complete successfully.

Examples

Create the GPIB object g associated with a National Instruments® GPIB controller with board index 0, and a Tektronix® TDS 210 oscilloscope with primary address 2.

g = gpib('ni',0,2);
g.InputBufferSize = 3000;

Connect g to the instrument, and write string commands that configure the scope to transfer binary waveform data from memory location A.

fopen(g)
fprintf(g,'DATA:DESTINATION REFA');
fprintf(g,'DATA:ENCDG SRPbinary');
fprintf(g,'DATA:WIDTH 1');
fprintf(g,'DATA:START 1');

Write the CURVE? command, which prepares the scope to transfer data, and read the data using the binblock format.

fprintf(g,'CURVE?')
data = binblockread(g);

More About

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Tips

Before you can read data from the instrument, it must be connected to obj with the fopen function. A connected interface object has a Status property value of open. An error is returned if you attempt to perform a read operation while obj is not connected to the instrument.

binblockread blocks the MATLAB Command Window until one of the following occurs:

  • The data is completely read.

  • The time specified by the Timeout property passes.

If msg is not included as an output argument and the read operation was not successful, then a warning message is returned to the command line.

Each time binblockread is issued, the ValuesReceived property value is increased by the number of values read.

Some instruments may send a terminating character after the binblock. binblockread will not read the terminating character. You can read the terminating character with the fread function. Additionally, if obj is a GPIB, VISA-GPIB, VISA-VXI, VISA-USB, or VISA-RSIB object, you can use the clrdevice function to remove the terminating character.

    Note:   If you do not set the terminator property to '' (null) before you execute fprintf or fwrite, binblockread may return incomplete data.

    Note:   To get a list of options you can use on a function, press the Tab key after entering a function on the MATLAB command line. The list expands, and you can scroll to choose a property or value. For information about using this advanced tab completion feature, see Using Tab Completion for Functions.

Introduced before R2006a

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