Table Of Contents

Graph IDE ► Laboratory ► Web Signal

Web Signal retrieves the source content from a URL you give it, then parses it and displays the selected numeric values as a time varying signal.

Here are some of the things you can do with it:

• Point it to your favorite stock web page and plot out price and volume in real time.
• Point it to a weather page such as the National Oceanic and Atmospheric Administration (NOAA) site and plot out temperature, humidity, dew point, wind speed or any other parameter.
• Point it to your laboratory instrumentation and plot out signal values (if your sensor has a web access point).
• Write a small cgi script to plot out anything on your computer.
• Write a small web server adapter interface to anything, anywhere, anytime and plot anything.

How To Use

Click the Tools > Configuration menu item to bring forward the state inspector and then modify the controls according to the following description:

Enter the Source URL you want and choose the channel number from the "Get New Source Sample" pull down button. That will retrieve the URL contents from the web and display it in the source text area.

Your next job is to take the source text and set the channel and pattern attributes to scan and acquire one or two numeric values. Each attribute will enable a data cursor (the position within the source text) to be advanced and get closer to the desired numeric value. Those attributes are defined as follows (one for each pattern and channel):

• Pattern: A unique piece of text in the source content to scan to.

• Skip Comments: If on, discards HTML comment sections in the source contents. If you change this then choose "Get New Source Sample" to see the processed source contents.

• Normalize Whites: If on, changes any blank, tab, and line feeds and consecutive sets of those into a single blank character in the source contents. If you change this then choose "Get New Source Sample" to see the processed source contents.

• Repeats: The number of times Pattern will be encountered before setting a data cursor. This sets the data cursor to the character after the last pattern matched.

• Delimiters: The number of times HTML command delimiters (a < and > pair) should be skipped in order to advance the data cursor past the last Pattern found. After doing that, the data cursor should now be set at the data numeric value to retrieve. It does not have to be exact as any leading non-digit character will be skipped, but it should be as close as possible to the data value.

• Skip Commas: If the numeric value to retrieve has commas in it (such as Volume: 33,000,000) then turn this on to remove the commas from the data value.

Note: The parameters above are to enable parsing of a fairly general web page. If you write a script to output two numbers then, of course, the source text will be very simple and the more complex parsing processing is completely unneeded.

Type in the titles for the graph.

Name the state, and then click the Apply button to start the data acquisition. If you previously named and applied a state and want to retrieve it then type the name in the state name field and click the Get button. The states are stored in your home folder in the ~/Library/Vvidget/Configuration/Web Signal folder.

Did you have trouble with Web Signal?

If you need assistance or have a comment regarding Web Signal please contact support@vvi.com.

About Web Signal

Web Signal is based on the Vvidget Signal Framework which is designed to show data from virtually any source. It has been used to display information ranging from stock feeds to real-time laboratory instrumentation and is adaptable to many data sources. For additional information contact info@vvi.com.