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Using the Direct I/O COM API of DriverLINX for the KPCI-PDISO8A or KPCI-
PIO32IOA with LabWindows/CVI

DriverLINX drivers for digital I/O boards provides two programming interfaces:
1. Service Request API for hardware independence with other KPCI or PIO boards
2. Direct I/O COM API for simple, fast interaction with the registers of the digital I/O hardware

COM objects are easily used from Visual Basic or from C++. Use of a COM object from a purely
C language such as CVI requires a bit more work to build a proper interface layer into the object.
Luckily, LabWindows/CVI provides an automated tool to greatly simplify creation of the interface
layer. The resulting function panel file, *.fp, can then be used in conventional ways by CVI to
make use of the function calls of the exposed object.

Below is a step by step guide. The completed project is also available as an example program in
the download center.

Step 1: In the Tools menu, select 'Create ActiveX Automation Controller....'
Step 2: Scroll down the list until you see the Keithley Digital I/O Library. Select it and then click
Next.
Step 3: Fill in a name for the target .fp file. Any name is fine; I used DirectIO (be sure to include
the path to the location). Then click the Next button.
Step 4: the object will be analyzed by CVI and several output files will be built and placed into the
directory location you specified. If any other dialogs present, accept the default values and click
Next. When complete, the screen below will appear.
Step 5: Now to use the object. From this same session of CVI, the function panel will already be
loaded in the Instrument Driver menu drop down. If starting a new session of CVI, first load the fp
file.
Step 6: Once the class has been selected, the member functions are visible. The important ones
are New, OpenDevice, CloseDevice, Read and Write. This was just a preview of where we
will be going, so hit the Cancel button for now.
Step 7: Create a project called testDirectIO. Add the DirectIO.fp file to the project. Add also a
uir file to the project. Place several buttons onto the user interface as shown below and create all
the callback code stubs (a *.c file is created).

In the call back for the Open Driver button, the Direct IO API will be initialized and a session
opened for the installed board (the device number used in the DriverLINX Configuration Panel will
be used).

In the Close Relays and Open Relays buttons, values will be written to the appropriate register of
the KPCI-PDISO8A or KPCI-PIO32IOA to control the state of the relays.

In the Exit button, the driver will be closed.

Step 8: Here is what the project will look like with it's three files.
Step 9: Let's use the fp file to add code to our .c file. Select the NewIKDigitalIo and then click the
Select button on the right.
Step 10: the screen below is presented to aid in the use of the function. Notice the variable
Object Handle is not filled in with a value. This indicates it needs to be declared by you. Select
this object with the mouse, and then ask CVI to declare the variable (Ctrl+D, or menu structure of
Code or the short cut buttons). (The Status variable could also be declared for a more robust
implementation that includes error checking, but for brevity, this is skipped in this application
note.)
Step 11: The following dialog is presented for declaring our object handle variable. Fill in a
variable name; I used myPIO. Also check the box indicating the declaration should be added to
the top of the target .c file for our project. Then click the OK button.

Step 12: Notice the field is now filled in with the proper calling syntax (address of operator). In
the .c file, place the curser within the callback function for the Open button, and then back on the
screen below ask CVI to "insert function call" using the Code menu structure.
Step 13: Below is a screen shot of the callback for the open button in the .c file after two
functions of the Direct IO COM object have been used. All subsequent methods of the Direct I/O
object require the Object Handle obtained from the NewIKDigitalIo method. Notice the syntax
used with the OpenDevice method (no & operator). Also notice that this method requires the
driver name as a string, "kpciiso", and the device number of the installed board from the
DriverLINX Configuration Panel. If more than one board of the kpciiso driver was installed, the
device number would be used to differentiate between them.

Once the object has been created and the driver opened for the installed device, the Read and
Write functions can be used to get data into and out of the KPCI card. You will need to know
something of the card's register map to know at what offsets (address) and what values to write.
For example, the relay outputs of the KPCI-PDISO8A are at an offset of 4. A value of 255 will
close all of them; a value of 0 will open all of them.

A complete CVI project is available in the download center of the www.keithley.com web site.