Read method

Description

VWorks software calls the Read method to tell the plugin to read the input signal (voltage) on the specified digital or analog input channel.

Syntax

 

HRESULT Read( [in,out] BSTR *xml, [out,retval] enum ReturnCode *retVal );

Parameters

 

xml

[in, out] The input xml parameter contains the following: • digitalInputs XML block with the name of a digital input channel • analogInputs XML block with the name of an analog input channel The output xml parameter contains the following: • digitalInput XML element with the input signal (voltage) on the specified digital input channel • analogInput XML element with the input signal (voltage) on the specified analog input channel

retVal

[out, retval] Returns an error code. Possible values: 0 = The request was completed (RETURN_SUCCESS) 1 = Something was wrong with the input, so the request was not completed (RETURN_BAD_ARGS) 2 = The request was not completed (RETURN_FAIL) For more information, see “ReturnCode enumerated type” .

Read method input

VWorks software passes one of the following XML blocks into the xml parameter of the Read method:

•	digitalInputs XML block

•	analogInputs XML block

The value of the file attribute of the Velocity11 element is Velocity11. See “Velocity11 element” .

digitalInputs XML block

The digitalInputs XML block contains the digitalInputs element and one name element. The name element contains the name of a digital input channel.

analogInputs XML block

The analogInputs XML block contains the analogInputs element and one name element. The name element contains the name of an analog input channel.

Example of Read method input received by the plugin

The following sample code is an analogInputs XML block that is received by the plugin from VWorks software as a string in the xml parameter of the Read method. VWorks software asks the plugin for the current input signal (voltage) on the analog input channel named Humidity.

 

<?xml version='1.0' encoding='ASCII' ?> <Velocity11 file='Velocity11' md5sum='dabdec8b39169630e4ff61e0388b5142' →version='1.1' > <analogInputs > <name >Humidity</name> </analogInputs> </Velocity11>

Read method output

The plugin returns a digitalInput XML element or an analogInput XML element in the xml parameter of the Read method.

digitalInput and analogInput elements

Each digitalInput and analogInput element has the following attributes:

 

Name	Value
name	The name of the input channel. Required: Yes
value	The current input signal (voltage). Required: Yes

Example of Read method input returned by the plugin

The following sample code contains an analogInput XML element that is returned by the plugin to VWorks software as a string in the xml parameter of the Read method. The code contains the current voltage of 70 volts for the analog input channel named Humidity.

 

<?xml version='1.0' encoding='ASCII' ?> <Velocity11 file='Velocity11' md5sum='cc239a8f99203e73b3de0ed8a058f77e' →version='1.1' > <analogInput name='Humidity' value='70' /> </Velocity11>

Related information

 

For information about...	See...
EnumPoints method	“EnumPoints method”
Set method	“Set method”