Question

I am working on a piece of arduino code that is using the BlackWidow version with wifi built in. Using the WiServer.h library, I’m using the SimpleClient.pde example with mods to send a call to a webserver that will simply return an integer – 0, 1, or 2. The end goal is to turn on a pin for the proper red, green, or yellow of a stoplight. The integers represent the aggregate state of our Hudson CI.

I’m a PHP lazy bastard, and pointers scare me. The code I am working with is

// Function that prints data from the server
void printData(char* data, int len) {

  // Print the data returned by the server
  // Note that the data is not null-terminated, may be broken up into smaller packets, and 
  // includes the HTTP header. 
  while (len-- > 0) {
    Serial.print(*(data++));
  }
}

printData() is the callback of the call to the webserver, and when run it sends the following to the serial monitor (this is 3 loops, no newline before new output):

HTTP/1.1 200 OK
Date: Thu, 10 Feb 2011 17:37:37 GMT
Server: Apache/2.2.13 (Unix) mod_ssl/2.2.13 OpenSSL/0.9.8k DAV/2 PHP/5.2.11
X-Powered-By: PHP/5.2.11
Content-Length: 1
Connection: close
Content-Type: text/html

0HTTP/1.1 200 OK
Date: Thu, 10 Feb 2011 17:37:45 GMT
Server: Apache/2.2.13 (Unix) mod_ssl/2.2.13 OpenSSL/0.9.8k DAV/2 PHP/5.2.11
X-Powered-By: PHP/5.2.11
Content-Length: 1
Connection: close
Content-Type: text/html

0HTTP/1.1 200 OK
Date: Thu, 10 Feb 2011 17:37:58 GMT
Server: Apache/2.2.13 (Unix) mod_ssl/2.2.13 OpenSSL/0.9.8k DAV/2 PHP/5.2.11
X-Powered-By: PHP/5.2.11
Content-Length: 1
Connection: close
Content-Type: text/html

0

The part that I need to identify is the 0, which could also be 1 or 2.

Instead of printData(), this function will become turnOnAppropriateLight() or something, by simply setting a pin to HIGH. This will then activate a relay, to power the corresponding LED array.

Now that I’ve written this up it looks like I just need to keep the last character around and do a switch based on the value. The *(data++) is the confusing part even though I know it’s incrementing a pointer index…I’m just not sure how to go directly to the last char in that index. No need for this looping to spit out the result.

Answer 1

This is not robust AT ALL, but

Serial.print(data[len-1])

See what that gets you