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Problem using program memory to store HTML in Arduino Webserver

neilk

I would appreciate some help with this very strange problem I'm having.

 

I've successfully adapted the very basic Web Server example supplied with the Ethernet Library to store all the HTML strings in program memory space, using the print(F("something"));

construct.

 

However, 1 issue remains unresolved: the very first HTML command in the page CANNOT be stored in program memory.

 

Thus:

  client.print("<!-- -->");                                            // This is a comment line, containing a blank comment; it makes the page work!

  client.println(F("<!DOCTYPE HTML>"

                 "<html>"

                 "<head>"

                 "<title>Arduino WEB Server Demo</title>"

                 "</head>"

                 "<body>"

                 "<h1>DEMO</h1>"));

 

works fine but without the blank comment line, it doesn't work, the HTML is not executed, but displayed in the browser window as text

 

  client.println(F("<!DOCTYPE HTML>"

                 "<html>"

                 "<head>"

                 "<title>Arduino WEB Server Demo</title>"

                 "</head>"

                 "<body>"

                 "<h1>DEMO</h1>"));

 

Does anyone have any ideas? I've tried inserting blank lines etc but nothing seems to fix it.

 

I've attached the full sketch

 

Many thanks

 

Neil

Attachments:
Simple_Web_Page_from_Program_Memory.ino.zip
  • 0

    I've done some work on this, storing the HTML commands into program memory as follows:

    .

    #include <avr/pgmspace.h>.

    .

    .

    const char webPage[] PROGMEM = "<!DOCTYPE HTML>"

                                                          "<html>"    

                                                          "<head>"    

                                                          "<title>Arduino WEB Server Demo</title>"

                                                          "</head>"

                                                          "<body>"

                                                          "<h1>DEMO</h1>";    

     

    I've written a routine to read this  data, 1 char at a time, from program space and output to the Web Client, using the pgm_read_byte() from avr/pgmspace.

    (I got the idea from:   http://todbot.com/blog/2008/06/19/how-to-do-big-strings-in-arduino/  Although if you look at the sketch fragment in this link, you will see that

    the HTML stored in PROGMEM is only output to the serial monitor (therefore as pure text!).

     

    \\

    \\ Output HTML stored in program memory to Ethernet Client

    \\

    void sendWebData(const prog_char str[])

    {

      char c;

      if(!str) return;

      while((c = pgm_read_byte(str++))) client.print(c);

    }

     

    Once again, this DOES NOT work, unless preceded by some other directly printed HTML command such as the blank comment line I used earlier.

     

    Anyone, please, any ideas??

     

    Neil