diff --git a/hal/api/Callback.h b/hal/api/Callback.h
new file mode 100644
index 0000000000..fa1f5ecc3f
--- /dev/null
+++ b/hal/api/Callback.h
@@ -0,0 +1,861 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2015 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef MBED_CALLBACK_H
+#define MBED_CALLBACK_H
+
+#include <string.h>
+#include <stdint.h>
+
+namespace mbed {
+
+
+/** Callback class based on template specialization
+ */
+template <typename F>
+class Callback;
+
+/** Templated function class
+ */
+template <typename R, typename A0, typename A1, typename A2, typename A3, typename A4>
+class Callback<R(A0, A1, A2, A3, A4)> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)(A0, A1, A2, A3, A4) = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*, A0, A1, A2, A3, A4)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)(A0, A1, A2, A3, A4)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R(A0, A1, A2, A3, A4)> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)(A0, A1, A2, A3, A4)) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*, A0, A1, A2, A3, A4)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)(A0, A1, A2, A3, A4)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R(A0, A1, A2, A3, A4)> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call(A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return _thunk(_obj, &_func, a0, a1, a2, a3, a4);
+    }
+
+    /** Call the attached function
+     */
+    R operator()(A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return call(a0, a1, a2, a3, a4);
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return static_cast<Callback<R(A0, A1, A2, A3, A4)>*>(func)
+                ->call(a0, a1, a2, a3, a4);
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return (*reinterpret_cast<R (**)(A0, A1, A2, A3, A4)>(func))
+                (a0, a1, a2, a3, a4);
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return (*reinterpret_cast<R (**)(T*, A0, A1, A2, A3, A4)>(func))
+                (static_cast<T*>(obj), a0, a1, a2, a3, a4);
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3, A4 a4) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)(A0, A1, A2, A3, A4)>(func)))
+                (a0, a1, a2, a3, a4);
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*, A0, A1, A2, A3, A4); 
+};
+
+/** Templated function class
+ */
+template <typename R, typename A0, typename A1, typename A2, typename A3>
+class Callback<R(A0, A1, A2, A3)> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)(A0, A1, A2, A3) = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*, A0, A1, A2, A3)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)(A0, A1, A2, A3)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R(A0, A1, A2, A3)> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)(A0, A1, A2, A3)) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*, A0, A1, A2, A3)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)(A0, A1, A2, A3)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R(A0, A1, A2, A3)> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call(A0 a0, A1 a1, A2 a2, A3 a3) {
+        return _thunk(_obj, &_func, a0, a1, a2, a3);
+    }
+
+    /** Call the attached function
+     */
+    R operator()(A0 a0, A1 a1, A2 a2, A3 a3) {
+        return call(a0, a1, a2, a3);
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func, A0 a0, A1 a1, A2 a2, A3 a3) {
+        return static_cast<Callback<R(A0, A1, A2, A3)>*>(func)
+                ->call(a0, a1, a2, a3);
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func, A0 a0, A1 a1, A2 a2, A3 a3) {
+        return (*reinterpret_cast<R (**)(A0, A1, A2, A3)>(func))
+                (a0, a1, a2, a3);
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3) {
+        return (*reinterpret_cast<R (**)(T*, A0, A1, A2, A3)>(func))
+                (static_cast<T*>(obj), a0, a1, a2, a3);
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2, A3 a3) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)(A0, A1, A2, A3)>(func)))
+                (a0, a1, a2, a3);
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*, A0, A1, A2, A3); 
+};
+
+/** Templated function class
+ */
+template <typename R, typename A0, typename A1, typename A2>
+class Callback<R(A0, A1, A2)> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)(A0, A1, A2) = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*, A0, A1, A2)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)(A0, A1, A2)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R(A0, A1, A2)> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)(A0, A1, A2)) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*, A0, A1, A2)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)(A0, A1, A2)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R(A0, A1, A2)> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call(A0 a0, A1 a1, A2 a2) {
+        return _thunk(_obj, &_func, a0, a1, a2);
+    }
+
+    /** Call the attached function
+     */
+    R operator()(A0 a0, A1 a1, A2 a2) {
+        return call(a0, a1, a2);
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func, A0 a0, A1 a1, A2 a2) {
+        return static_cast<Callback<R(A0, A1, A2)>*>(func)
+                ->call(a0, a1, a2);
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func, A0 a0, A1 a1, A2 a2) {
+        return (*reinterpret_cast<R (**)(A0, A1, A2)>(func))
+                (a0, a1, a2);
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2) {
+        return (*reinterpret_cast<R (**)(T*, A0, A1, A2)>(func))
+                (static_cast<T*>(obj), a0, a1, a2);
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func, A0 a0, A1 a1, A2 a2) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)(A0, A1, A2)>(func)))
+                (a0, a1, a2);
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*, A0, A1, A2);
+};
+
+/** Templated function class
+ */
+template <typename R, typename A0, typename A1>
+class Callback<R(A0, A1)> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)(A0, A1) = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*, A0, A1)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)(A0, A1)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R(A0, A1)> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)(A0, A1)) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*, A0, A1)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)(A0, A1)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R(A0, A1)> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call(A0 a0, A1 a1) {
+        return _thunk(_obj, &_func, a0, a1);
+    }
+
+    /** Call the attached function
+     */
+    R operator()(A0 a0, A1 a1) {
+        return call(a0, a1);
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func, A0 a0, A1 a1) {
+        return static_cast<Callback<R(A0, A1)>*>(func)
+                ->call(a0, a1);
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func, A0 a0, A1 a1) {
+        return (*reinterpret_cast<R (**)(A0, A1)>(func))
+                (a0, a1);
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func, A0 a0, A1 a1) {
+        return (*reinterpret_cast<R (**)(T*, A0, A1)>(func))
+                (static_cast<T*>(obj), a0, a1);
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func, A0 a0, A1 a1) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)(A0, A1)>(func)))
+                (a0, a1);
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*, A0, A1); 
+};
+
+/** Templated function class
+ */
+template <typename R, typename A0>
+class Callback<R(A0)> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)(A0) = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*, A0)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)(A0)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R(A0)> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)(A0)) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*, A0)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)(A0)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R(A0)> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call(A0 a0) {
+        return _thunk(_obj, &_func, a0);
+    }
+
+    /** Call the attached function
+     */
+    R operator()(A0 a0) {
+        return call(a0);
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func, A0 a0) {
+        return static_cast<Callback<R(A0)>*>(func)
+                ->call(a0);
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func, A0 a0) {
+        return (*reinterpret_cast<R (**)(A0)>(func))
+                (a0);
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func, A0 a0) {
+        return (*reinterpret_cast<R (**)(T*, A0)>(func))
+                (static_cast<T*>(obj), a0);
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func, A0 a0) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)(A0)>(func)))
+                (a0);
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*, A0); 
+};
+
+/** Templated function class
+ */
+template <typename R>
+class Callback<R()> {
+public:
+    /** Create a Callback with a static function
+     *  @param func Static function to attach
+     */
+    Callback(R (*func)() = 0) {
+        attach(func);
+    }
+
+    /** Create a Callback with a static function and bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (*func)(T*)) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    Callback(T *obj, R (T::*func)()) {
+        attach(obj, func);
+    }
+
+    /** Create a Callback with another Callback
+     *  @param func Callback to attach
+     */
+    Callback(const Callback<R()> &func) {
+        attach(func);
+    }
+
+    /** Attach a static function
+     *  @param func Static function to attach
+     */
+    void attach(R (*func)()) {
+        memcpy(&_func, &func, sizeof func);
+        _thunk = func ? &Callback::_staticthunk : 0;
+    }
+
+    /** Attach a static function with a bound pointer
+     *  @param obj  Pointer to object to bind to function
+     *  @param func Static function to attach
+     */
+    template <typename T>
+    void attach(T *obj, R (*func)(T*)) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_boundthunk<T>;
+    }
+
+    /** Attach a member function
+     *  @param obj  Pointer to object to invoke member function on
+     *  @param func Member function to attach
+     */
+    template<typename T>
+    void attach(T *obj, R (T::*func)()) {
+        _obj = static_cast<void*>(obj);
+        memcpy(&_func, &func, sizeof func);
+        _thunk = &Callback::_methodthunk<T>;
+    }
+
+    /** Attach a Callback
+     *  @param func The Callback to attach
+     */
+    void attach(const Callback<R()> &func) {
+        _obj = func._obj;
+        memcpy(&_func, &func._func, sizeof _func);
+        _thunk = func._thunk;
+    }
+
+    /** Call the attached function
+     */
+    R call() {
+        return _thunk(_obj, &_func);
+    }
+
+    /** Call the attached function
+     */
+    R operator()() {
+        return call();
+    }
+
+    /** Test if function has been attached
+     */
+    operator bool() const {
+        return _thunk;
+    }
+
+    /** Static thunk for passing as C-style function
+     *  @param func Callback to call passed as void pointer
+     */
+    static R thunk(void *func) {
+        return static_cast<Callback<R()>*>(func)
+                ->call();
+    }
+
+private:
+    // Internal thunks for various function types
+    static R _staticthunk(void*, void *func) {
+        return (*reinterpret_cast<R (**)()>(func))
+                ();
+    }
+
+    template<typename T>
+    static R _boundthunk(void *obj, void *func) {
+        return (*reinterpret_cast<R (**)(T*)>(func))
+                (static_cast<T*>(obj));
+    }
+
+    template<typename T>
+    static R _methodthunk(void *obj, void *func) {
+        return (static_cast<T*>(obj)->*
+                (*reinterpret_cast<R (T::**)()>(func)))
+                ();
+    }
+
+    // Stored as pointer to function and pointer to optional object
+    // Function pointer is stored as union of possible function types
+    // to garuntee proper size and alignment
+    struct _class;
+    union {
+        void (*_staticfunc)();
+        void (*_boundfunc)(_class *);
+        void (_class::*_methodfunc)();
+    } _func;
+
+    void *_obj;
+
+    // Thunk registered on attach to dispatch calls
+    R (*_thunk)(void*, void*); 
+};
+
+
+} // namespace mbed
+
+#endif
diff --git a/hal/api/mbed.h b/hal/api/mbed.h
index 9540ba65b4..8d615d4c6f 100644
--- a/hal/api/mbed.h
+++ b/hal/api/mbed.h
@@ -64,6 +64,9 @@
 #include "sleep_api.h"
 #include "rtc_time.h"
 
+// mbed Non-hardware components
+#include "Callback.h"
+
 using namespace mbed;
 using namespace std;