viBufRead

NI-VISA 15.0 Help

Edition Date: June 2015

Part Number: 370131S-01

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Purpose

Reads data from device or interface through the use of a formatted I/O read buffer.

C Syntax

ViStatus viBufRead(ViSession vi, ViPBuf buf, ViUInt32 count, ViPUInt32 retCount)

Visual Basic Syntax

viBufRead&(ByVal vi&, ByVal buf$, ByVal count&, retCount&)

Resource Classes

GPIB INSTR, GPIB INTFC, Serial INSTR, TCPIP INSTR, TCPIP SOCKET, USB INSTR, USB RAW, VXI INSTR, VXI SERVANT

Parameters

Name Direction Description

vi

IN

Unique logical identifier to a session.

buf

OUT

Location of a buffer to receive data from device.

count

IN

Number of bytes to be read.

retCount

OUT

Number of bytes actually transferred.

Return Values

Completion Codes Description

VI_SUCCESS

The operation completed successfully and the END indicator was received (for interfaces that have END indicators). This completion code is returned regardless of whether the termination character is received or the number of bytes read is equal to count.

VI_SUCCESS_TERM_CHAR

The specified termination character was read but no END indicator was received. This completion code is returned regardless of whether the number of bytes read is equal to count.

VI_SUCCESS_MAX_CNT

The number of bytes read is equal to count. No END indicator was received and no termination character was read.

Error Codes Description

VI_ERROR_INV_OBJECT

The given session reference is invalid.

VI_ERROR_NSUP_OPER

The given vi does not support this operation.

VI_ERROR_RSRC_LOCKED

Specified operation could not be performed because the resource identified by vi has been locked for this kind of access.

VI_ERROR_TMO

Timeout expired before operation completed.

VI_ERROR_IO

An unknown I/O error occurred during transfer.

Description

The viBufRead() operation is similar to viRead() and does not perform any kind of data formatting. It differs from viRead() in that the data is read from the formatted I/O read buffer—the same buffer used by viScanf() and related operations—rather than directly from the device. You can intermix this operation with viScanf(), but you should not mix it with viRead().

VI_NULL is a special value for the retCount parameter. If you pass VI_NULL for retCount, the number of bytes transferred is not returned. You may find this useful if you need to know only whether the operation succeeded or failed.

Note Note  The retCount and buf parameters always are valid on both success and error.


Related Topics

INSTR Resource

INTFC Resource

SERVANT Resource

SOCKET Resource

viBufWrite

viRead

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