()()

Agilent VISA.NET

()()

Syntax

viOpen(int sesn, string viDesc, int mode, int timeout, out int vi);

Description

Opens a VISA resource session given a VISA Resource Manager session, a resource address, and resource locking information. If successful, it returns a session identifier (integer) that can be used to execute any other legal operations on that resource.

Parameters

Name	Dir	Type	Description
sesn	IN	int	Resource Manager session (should always be the Default Resource Manager for VISA returned from viOpenDefaultRM).
viDesc	IN	string	Unique symbolic name of a resource. (See the viOpen topic in the VISA Help for details..)
mode	IN	int	Specifies the modes by which the resource is to be accessed. The value VI_EXCLUSIVE_LOCK is used to acquire an exclusive lock immediately upon opening a session. If a lock cannot be acquired, the session is closed and an error is returned. The VI_LOAD_CONFIG value is used to configure attributes specified by some external configuration utility. If this value is not used, the session uses the default values provided by this specification. Multiple access modes can be used simultaneously by specifying a "bit-wise OR" of the values. (Must use VI_NULL in VISA 1.0.)
timeout	IN	int	If the accessMode parameter requires a lock, this parameter specifies the absolute time period (in milliseconds) that the resource waits to get unlocked before this operation returns an error. Otherwise, this parameter is ignored. (Must use VI_NULL in VISA 1.0.)
vi	OUT	out int	Unique logical identifier reference to a session.

Return Values

Completion Codes	Description
VI_SUCCESS	Operation completed successfully.
VI_SUCCESS_DEV_NPRESENT	Session opened successfully, but the device at the specified address is not responding.
VI_WARN_CONFIG_NLOADED	The specified configuration either does not exist or could not be loaded using VISA-specified defaults.
Error Codes	Description
VI_ERROR_ALLOC	Insufficient system resources to open a session.
VI_ERROR_INTF_NUM_NCONFIG	The interface type is valid but the specified interface number is not configured.
VI_ERROR_INV_ACC_MODE	Invalid access mode.
VI_ERROR_INV_RSRC_NAME	Invalid resource reference specified. Parsing error.
VI_ERROR_INV_SESSION VI_ERROR_INV_OBJECT	The given session or object reference is invalid (both are the same value).
VI_ERROR_LIBRARY_NFOUND	A code library required by VISA could not be located or loaded.
VI_ERROR_NSUP_OPER	The given sesn does not support this function. For VISA, this function is supported only by the Default Resource Manager session.
VI_ERROR_RSRC_BUSY	The resource is valid but VISA cannot currently access it.
VI_ERROR_RSRC_LOCKED	Specified type of lock cannot be obtained because the resource is already locked with a lock type incompatible with the lock requested.
VI_ERROR_RSRC_NFOUND	Insufficient location information or resource not present in the system.
VI_ERROR_TMO	A session to the resource could not be obtained within the specified timeout period.

C# Example

public int OpenSession(string resourceAddress, int resourceManager)
{
	int session, viError;
	viError = visa32.viOpen(resourceManager, resourceAddress, 
				visa32.VI_NO_LOCK, 
				visa32.VI_TMO_IMMEDIATE, out session);
	if (viError < visa32.VI_SUCCESS)
	{
		System.Text.StringBuilder error = 
					new System.Text.StringBuilder(256);
		visa32.viStatusDesc(resourceManager, viError, error);
		throw new ApplicationException(error.ToString());
	}
	return session;
}

VB .NET Example

Public Function OpenSession(ByVal resourceAddress As String, _
			    ByVal resourceManager As Integer) As Integer
    Dim session As Integer = 0, viError As Integer
    viError = visa32.viOpen(resourceManager, resourceAddress, _
			    visa32.VI_NO_LOCK, _
			    visa32.VI_TMO_IMMEDIATE, session)
    If viError < visa32.VI_SUCCESS Then
        Dim err As System.Text.StringBuilder = New System.Text.StringBuilder(256)
        visa32.viStatusDesc(resourceManager, viError, err)
        Throw New ApplicationException(err.ToString())
    End If
    Return session
End Function

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