WinCC OA tag (interpreter string)

Simple queries

• Compile and display text (without prefix "?"). Square braces stand for any text below.

Display the name of the $parameter $dpe on the HTML page. So far, these have only been current contents and fixed texts. In order to display the name of the $parameter, the query in the HTML reference would have to look as any of the following two:

<%"data point element: "+$dpe%>

or

data point element: <%$dpe%>

or for fixed data point elements

data point element: <%"dp1"%>

• Querying DPE values, times and all other attributes (with prefix "?"). Again, braces stand for any text.

Example

Display the online value of the ".regratio" of the DP in the $parameter "$dp" on the HTML page. The appropriate query in the HTML reference looks as this:

Value: <%?$dp+".regratio"%>

with format and unit or

Value: <%?$dp+".regratio:_online.._value"%>

Without format and unit and, additionally, display the DP comment for the DPE:

Comment: <%?$dp+".regratio".comment%>

Example

Make a table cell take on the alert handling color of a DPE:

<table><tr>

<td bgcolor="<%?$dpe.alertColor%>">Cell contents</td>

</tr></table>

Complex queries

You can also make use of $parameters passed to the reference in functions and scripts called on the server when creating dynamic pages. The following additional $parameters are always passed:

• Execute CTRL functions (prefix "=")

Example

Make a table cell containing "Text" take on the color "_invalid". The appropriate query in the HTML reference looks like this:

1. <table><tr>

   <td bgcolor="<%=http_color("_invalid")%>">Text</td>

   </tr></table>

• Execute control script (Prefix "={")

Executes a complex WinCC OA script in which the specified $parameters and all functions from the proj_http.ctl library are known.

Example

Read and subtract the online values of two DPEs in the $parameters "$dpe1" and "$dpe2" and return the result as an HTML string. The appropriate script in the HTML reference looks as:

<%=
{
  string sHtml;
  http_sub(sHtml); 
  return(sHtml); 
}
%>
This requires the following function in the CONTROL library:
void http_sub(string &html)
{
  float f1, f2;
  dpGet($dpe1+":_online.._value", f1,$dpe2+":_online.._value", f2);
  sprintf(html, "%5.2f - %5.2f = <b>%5.2f</b>", f1, f2,(f1-f2));
}

Example

Display an image (LED) on the HTML page depending on the invalid bit of the data point in the $parameter $dpe. The appropriate script in the HTML reference looks as this:

<%$dpe%>: <img align="middle" src="/pictures/http/<%={string s;
http_bool(s, $dpe+":_online.._bad", "led_invalid", "led_active");
return(s);}%>.gif"> 
<br>
This requires the following function in the library:
void http_bool(string &sHtml, string sDpe,
string sImgOn, string sImgOff)
{
  bool b;
  dpGet(sDpe, b);
  sHtml= ( b ? sImgOn : sImgOff );
}