Write and Read Binary Data Using VISA

This example explores binary read and write operations with a VISA object using a Tektronix® TDS210 oscilloscope.

The VISA object supports seven interfaces: serial, GPIB, VXI, PXI, USB, Serial, TCP/IP, and Socket. This example explores binary read and write operations using a VISA-GPIB object. However, binary read and write operations for all interfaces are identical to each other. Therefore, you can use the same commands. The only difference is the resource name specified in the VISA constructor visadev.

Binary read and write operations for the VISA-Serial object are identical to binary read and write operations for the serial port object. Therefore, to learn how to perform binary read and write operations for the VISA-Serial object, refer to Write and Read Serial Port Data.

Connect to Instrument

Create a VISA-GPIB object using the VISA resource string shown below.

v = visadev("GPIB0::2::INSTR")
v = 

  GPIB with properties:

         ResourceName: "GPIB0::2::INSTR"
                Alias: "OSCOPE"
               Vendor: "TEKTRONIX"
                Model: "TDS 210"
           BoardIndex: 0
       PrimaryAddress: 1
     SecondaryAddress: 0

  Show all properties, functions

Write Binary Data

Use the write function to write binary data to the instrument. The following commands configure and then send a sine wave to the instrument.

writeline(v,"Data:Destination RefB");
writeline(v,"Data:Encdg SRPbinary");
writeline(v,"Data:Width 2";
writeline(v,"Data:Start 1");

t = (0:499) .* 8 * pi / 500;
data = round(sin(t) * 90 + 127);
writeline(v,"CURVE #3500");

write(v,data,"int16")

The write function suspends MATLAB® execution until all the data is written or a timeout occurs as specified by the Timeout property of the visadev object.

By default, the write function writes binary data as uint8 data. For more information about specifying other data types, see write.

Note

When performing a write operation, you should think of the transmitted data in terms of values rather than bytes. A value consists of one or more bytes. For example, one uint32 value consists of four bytes.

Read Binary Data

Use the read function to read binary data from the instrument. Use the following commands to read the sine wave from the instrument.

writeline(v,"Data:Source CH1");
writeline(v,"Data:Encdg SRIbinary");
writeline(v,"Data:Width 2");
writeline(v,"Data:Start 1");
writeline(v,"Curve?")

data = read(v,1200,"int16");

The read function suspends MATLAB execution until one of the following occurs:

  • A timeout occurs as specified by the Timeout property

  • The input buffer is filled

  • The specified number of values is read

  • The EOI line is asserted

  • The terminator is received as specified by the Terminator property

By default, the read function reads binary data as uint8 data. For more information about specifying other data types, see read.

Note

When performing a read operation, you should think of the received data in terms of values rather than bytes. A value consists of one or more bytes. For example, one uint32 value consists of four bytes.

Clean Up

When you are finished with the VISA-GPIB object, clear it.

clear v

See Also

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