Re: HTML Device Driver

[Rod Nussbaumer <bomr@triumf.ca>]

David Dudley wrote:
> Here’s a new one for you (Got Ralph and Michael going about how to do 
> it, anyway ;-)
>
> Almost all of the PLC equipment we’re going to be using on NSLS/2 is 
> connected on Ethernet.
>
> It is common practice in the communications modules now, to integrate an 
> embedded WEB server into the device.  Both the Siemens and Rockwell 
> hardware we’re going to use have that capability, as well as most of the 
> new generation of instrumentation.
>
> Does anyone have knowledge of an EPICS device driver that is capable of 
> reading and interpreting a WEB page or XML page?  Seems that this would 
> be the most universal way to read data from all this differing 
> equipment, if such a driver was available.
>
> David Dudley

I used StreamDevice + Asyn to acquire data from an ethernet attached 
instrument containing a built-in web server. It required a minor bit of 
reverse engineering the HTML code, which was quite simple, and took just 
a little bit of tutoring from Dirk to get things right. Although the 
server was not intended for this purpose, the scheme worked well enough.

In the second design iteration of the instrument, they changed the web 
interface to make it more user friendly. It now uses a Java applet which 
downloads to the browser, and the applet communicates with the server, 
or some such stuff that is indecipherable from the standpoint of EPICS 
support. Given a second lifetime, I might get around to creating EPICS 
support capable of dealing with that problem. Is an evolving standard 
like HTML a good thing to rely on for a control system?

Rod Nussbaumer
ISAC Controls, TRIUMF
Vancouver, Canada