viWrite

Syntax

viWrite(ViSession vi, ViBuf buf, ViUInt32 count, ViPUInt32 retCount);

Description

This function synchronously transfers data to a device. The data to be written is in the buffer represented by buf. This function returns only when the transfer terminates. Only one synchronous write function can occur at any one time. If you pass VI_NULL as the retCount parameter to the viWrite operation, the number of bytes transferred will not be returned. This may be useful if it is important to know only whether the operation succeeded or failed.

If you are using viWrite in Visual Basic 6, see Notes on Using viRead/viWrite in Visual Basic 6 for information on modifying its declaration to allow efficient reading and writing of numeric arrays.

Parameters

Name	Dir	Type	Description
vi	IN	ViSession	Unique logical identifier of a session.
buf	IN	ViBuf	Represents the location of a data block to be sent to device.
count	IN	ViUInt32	Specifies number of bytes to be written.
retCount	OUT	ViPUInt32	Represents the location of an integer that will be set to the number of bytes actually transferred.
Special Value for retCount Parameter
Value			Description
VI_NULL			Do not return the number of bytes transferred.

Return Values

Completion Code	Description
Type ViStatus	This is the function return status. It returns either a completion code or an error code as follows.
VI_SUCCESS	Transfer completed.
Error Code	Description
VI_ERROR_BERR	Bus error occurred during transfer.
VI_ERROR_CONN_LOST	The I/O connection for the given session has been lost.
VI_ERROR_INP_PROT_VIOL	Device reported an input protocol error occurred during transfer.
VI_ERROR_INV_SESSION VI_ERROR_INV_OBJECT	The given session or object reference is invalid (both are the same value).
VI_ERROR_INV_SETUP	Unable to start write function because setup is invalid (due to attributes being set to an inconsistent state).
VI_ERROR_IO	Unknown I/O error occurred during transfer.
VI_ERROR_NCIC	The interface associated with the given vi is not currently the controller in charge.
VI_ERROR_NLISTENERS	No Listeners condition is detected (both NRFD and NDAC are de-asserted).
VI_ERROR_NSUP_OPER	The given vi does not support this function.
VI_ERROR_RAW_RD_PROT_VIOL	Violation of raw read protocol occurred during transfer.
VI_ERROR_RAW_WR_PROT_VIOL	Violation of raw write protocol occurred during transfer.
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 function completed.

C# Example

public int WriteBytes(int session, int requestCount, byte[] data)
{
	int viError, outCount;
	viError = visa32.viWrite(session, data, requestCount, out outCount);
	if (viError < visa32.VI_SUCCESS)
	{
		System.Text.StringBuilder error = 
					new System.Text.StringBuilder(256);
		visa32.viStatusDesc(session, viError, error);
		throw new ApplicationException(error.ToString());
	}
	return outCount;
}

VB .NET Example

Public Function WriteBytes(ByVal session As Integer, _
			   ByVal requestCount As Integer, _
			   ByVal data() As Byte) As Integer
    Dim viError As Integer, outCount As Integer = 0
    viError = visa32.viWrite(session, data, requestCount, outCount)
    If viError < visa32.VI_SUCCESS Then
        Dim err As System.Text.StringBuilder = New System.Text.StringBuilder(256)
        visa32.viStatusDesc(session, viError, err)
        Throw New ApplicationException(err.ToString())
    End If
    Return outCount
End Function