LeafLabs Garden

A place to share, learn, and grow...

1. 

   jstamour802
   Member

   how do I get the String class working? My IDE is 0.0.12 (Arduino 0018).

   I know that Arduino 0019 has the string class,but the latest maple IDE doesnt include it.

   What do I need to do to get String to work?

   Posted 1 year ago #
2. 

   jstamour802
   Member

   More specifically, I need to retrieve an integer from a string. I'm working on a web server interface that sends the value of a number field in a string like this:

   "GET /ajax_inputs&PWM3=1000&nocache=120749.0530796349"

   I need to extract the "1000" from "PWM3=1000" in the string, and use that value to write to a PWM pin.

   The string library in Arduino (or the standard C string library for that matter) can do it by the substring method, but is there a different way I can do it without the bloat of the string library?

   Posted 1 year ago #
3. 

   ventosus
   Member

   This should be straight-forward with the C functions 'strstr' and 'atoi'.

   
extern "C" {
#include <string.h>
#include <stdlib.h>

   char *req = "GET /ajax_inputs&PWM3=1000&nocache=120749.0530796349";
char *ptr = strstr(req, "PWM3=");
if(ptr)
{
int pwn = atoi(ptr+5);
// use pwn
}
}


   Posted 1 year ago #
4. 

   ventosus
   Member

   Or using sscanf...

   
extern "C" {
#include <stdio.h>
int pwn;
sscanf(req, "GET /ajax_inputs&PWM3=%i", &pwn);
printf("%i\n", pwn);
}


   Posted 1 year ago #
5. 

   jstamour802
   Member

   ventosus - thank you for your answers. I tried the first example on Arduino and it works well.

   I then tried it on maple but I get 'atoi' not declared. How do I add 'atoi'? I found this from the FAQ:

   "How can I use atoi()?
   The CodeSourcery GCC compiler used to compile your programs is configured to link against the newlib C library, and allows the use of any of its headers."

   This doesn't tell me much...nor how to make it compile in my program. Is there another step I need to use 'atoi'?

   Also, I dont have 'String.h'. Where does this library come from?

   Posted 1 year ago #
6. 

   jstamour802
   Member

   Also If I try to include <stdlib.h> I get:

   \maple-ide-0.0.12-windowsxp32\hardware\tools\arm\bin\../lib/gcc/arm-none-eabi/4.4.1/../../../../arm-none-eabi/include/stdlib.h:72

   stdlib.h:72: error: expected unqualified-id before 'int'

   Posted 1 year ago #
7. 

   jstamour802
   Member

   I was able to get <stdlib> to work, I had to add it at the top of my includes

   <stdlib>
   ...
   <other includes>

   Otherwise it didnt work.

   The program compiles now, but now your first example doesn't work. It returns a blank value instead of the int. It worked for Arduino however.

   Also, I cant figure out where to put extern 'C' { without causing problems in my program. What exactly needs to be within the braces?

   Thanks in advance for any help.

   Posted 1 year ago #
8. 

   ventosus
   Member

   @jstamour802

   I put the 'extern "C"' there only to tell you that this is C code and may need adaptations to run in wirish/C++, and obviously you have found out exactly that ;-)

   So forget about the 'extern "C".
   IIRC, the right way to include C headers stdlib.h, string.h or stdio.h in C++ is:
   #include <cstdlib>
   #include <cstring>
   #include <cstdio>

   I have actually tested both ways and they work fine here.
   But I use the current launchpad GCC instead of the outdated codesourcery GCC...

   Posted 1 year ago #
9. 

   jstamour802
   Member

   thanks a ton for your help - I was able to get everything to work. This put me over a major hump in a project I am working on.

   high five!

   Posted 1 year ago #

RSS feed for this topic

Reply

You must log in to post.