Specifications

Possible values for this parameter are:

Value

Meaning

HTTP_START_OF_VAR

This is the very first callback for

given variable for the current

instance. If a multi-byte data

transfer is required, this value

should be used to conditionally

initialize index to the multi-byte

array that will be transferred for

current variable

For all others

Main application specific value.

val [out]

One byte of data that is to be transferred

Return Values

New reference value as determined by main application. If this value is other

than HTTP_END_OF_VAR, HTTP will call this function again with return value

from previous call.

If HTTP_END_OF_VAR is returned, HTTP will not call this function and

assumes that variable value transfer is finished.

Possible values for this parameter are:

Value

Meaning

HTTP_END_OF_VAR

This is a last data byte for given variable.

HTTP will not call this function until

another variable value is needed.

For all Others

Main application specific value.

Pre-Condition

None

Figure 18 CGI Page Calling the HTTPGetVar Function

With the information provided by the previously introduced function, we are able

to provide real time data from the microcontroller to the user via a dynamically

updating web page. Figure 19 shown below is an example of one such

implementation.

“status.cgi” contains following HTML line:

…

…

Figure 19 Dynamically Updated Web Page using HTML code