Installation and operating manual for WATERFRIEND exclusive MRD-2 Page 41 (44)
Interfacing with building automation systems
The MRD-2 contains an HTTP web server, which is designed to allow the control unit to be operated using any
web browser from any web-enabled terminal.
The HTML pages generated by this web server can also be accessed by a building automation system and can
be interpreted for display on EIB visualization devices. For the purpose of controlling the MRD-2, the building
automation system can generate IP messages, in the same way as they would be generated by a web browser
when you click on controls on the HTML pages. In other words, the building automation system must emulate a
web browser.
Instead of using directly the predefined HTML pages designed by
for displaying on web browsers, you (as
user) can also design your own control file to obtain the data you require in "custom" form, and save this file on
the SD card in the MRD-2. This means that the interface to the building automation system is then unaffected by
potential design changes to the
HTML pages.
This control file must be saved as an ASCII text file with the extension ".HTM" in the "HTML" folder on the SD
card. The file name must not exceed 8 characters in length. Although it has the "HTM" extension, this file need not
necessarily be a valid HTML file, but can be formatted to suit the requirements of the building automation system.
This control file can contain variables in the format "$$nnnn", which the web server then replaces with the data
that is currently valid. A list of available variables appears at the end of this document.
A control file "ISTWERTE.HTM" containing the following:
pH value: $$0001 pH
ORP value: $$0003 mV
would, on opening “http://xxx.xxx.xxx.xxx/istwerte.htm", return the following text for example:
pH value: 7.26 pH
ORP value: 689 mV
These control files can also be used selectively to read specific datapoints, e.g. "REDOX.HTM" containing the
following:
$$0003
returns
689
In order to make changes to data in the control unit from the building automation system, the building automation
system must emulate sending an HTML form. This is done by a URL invocation in the form
"http://xxx.xxx.xxx.xxx/modify?nnnn=data", where nnnn is the number of the variable to be changed, and data
represents the data to be stored.
Before the building automation system can change any variables, it must first log in by sending a valid PIN
number to the variable 0003:
„http://xxx.xxx.xxx.xxx/modify?0000=dddd“, where dddd is the user PIN configured in the unit.
Variables can be set after successful login, e.g. set the ORP value to 650 mV:
„http://xxx.xxx.xxx.xxx/modify? 0013=650“.
Afterwards, the building automation system should log out by writing to the variable 0003 again with any invalid
value:
„http://xxx.xxx.xxx.xxx/modify?0000=0000“
A similar call sequence can be used, for example, to switch the operating mode of the redox control:
„http://xxx.xxx.xxx.xxx/modify?0000=dddd“
Login
„http://xxx.xxx.xxx.xxx/modify?0032=i“
Switch operating mode
„http://xxx.xxx.xxx.xxx/modify?0000=0000“
Logout
