Instruction manual

Using the COM Server

Using the COM server will only work on Windows computers. You'll need to install python, pyserial,

and pywin32; please refer to the appendices for instructions.

Here's a summary of the things we'll do in this section:

1. Connect a power supply to the computer.

2. Register the COM server.

3. Run a python script to access the power supply via the COM server.

4. Use Visual Basic to access the power supply via the COM server

Connect the DC load

Connect a power supply using either a serial port on your computer or the USB to serial device. If

you use the USB to serial device (IT-E132), you'll need to install the PL-2302 driver on the CD that

came with the IT-E132 device.

Make sure the power supply is powered on.

Registering the COM server means telling Windows about the server. This only needs to be done

once and it will be remembered across power cycles. One condition, however, is that the

ps178x.py file must not be moved or deleted; otherwise, the functionality will not be accessible

through COM.

The easiest way to register the COM server is to open an Explorer window, navigate to the directory

containing the python files in this software package, then double-click on the ps178x.py file. A DOS

window will open momentarily, then disappear, probably too fast for you to see what happened.

If instead you wish to see what happens during registration, open a DOS window and go to the

directory that has the python file ps178x.py that came with this software package.

Execute the command python ps178x.py. You should see the message

Registered: BKServers.px178x

This means the COM server has been registered with the operating system. Now an application can

request a connection to a COM server named BKServers.px178x and the operating system will

start the ps178x.py script when such a connection is requested.

If you wish to unregister the COM server, execute the command

python ps178x.py --unregister.

You'd unregister, for example, if you wanted to move the ps178x.py script somewhere else, then re-

Use python to access the COM server

In a DOS window, go to the directory that has the python file test.py that came with this software

package. Run the command python test.py com p br. Here, p is the COM (RS-232

communications) port the DC load is connected to and br is the baudrate. You should see output

similar to the following (of course, your numbers will differ):

Time from Power Supply = Fri Dec 19 12:01:32 2008

Set to remote control

Set max voltage

B&K 1785, 1786B, 1787B, 1788 Python Library 15 January 2009 Page 9 of 14