FPointer Class Reference

FPointer - Adds callbacks that take and return a 32bit uint32_t data type. More...

#include <FPointer.h>

Detailed Description

FPointer - Adds callbacks that take and return a 32bit uint32_t data type.

The Mbed library supplies a callback using the FunctionPointer object as defined in FunctionPointer.h However, this callback system does not allow the caller to pass a value to the callback. Likewise, the callback itself cannot return a value.

FPointer operates in the same way but allows the callback function to be passed one arg, a uint32_t value. Additionally, the callback can return a single uint32_t value. The reason for using uint32_t is that the Mbed and the microcontroller (LPC1768) have a natural data size of 32bits and this means we can use the uint32_t as a pointer. See example1.h for more information. This example passes an "int" by passing a pointer to that int as a 32bit value. Using this technique you can pass any value you like. All you have to do is pass a pointer to your value cast to (uint32_t). Your callback can the deference it to get the original value.

example2.h shows how to do the same thing but demostrates how to specify the callback into a class object/method.

Finally, example3.h shows how to pass multiple values. In this example we define a data structure and in the callback we pass a pointer to that data structure thus allowing the callback to again get the values.

Note, when passing pointers to variables to the callback, if the callback function/method changes that variable's value then it will also change the value the caller sees. If C pointers are new to you, you are strongly advised to read up on the subject. It's pointers that often get beginners into trouble when mis-used.

See also:

example1.h

example2.h

example3.h

http://mbed.org/handbook/C-Data-Types

http://mbed.org/projects/libraries/svn/mbed/trunk/FunctionPointer.h

Definition at line 66 of file FPointer.h.

Constructor & Destructor Documentation

Member Function Documentation

 uint32_t myCallbackFunction(uint32_t);

     public:
         uint32_t myCallbackFunction(uint32_t);

Field Documentation