diff --git a/drivers/AnalogIn.h b/drivers/AnalogIn.h
index c9ccfa25a1..f634fa5ee0 100644
--- a/drivers/AnalogIn.h
+++ b/drivers/AnalogIn.h
@@ -114,7 +114,7 @@ public:
     }
 
 protected:
-
+    #if !defined(DOXYGEN_ONLY)
     virtual void lock()
     {
         _mutex->lock();
@@ -127,6 +127,7 @@ protected:
 
     analogin_t _adc;
     static SingletonPtr<PlatformMutex> _mutex;
+    #endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed
diff --git a/drivers/AnalogOut.h b/drivers/AnalogOut.h
index 3945c580c4..2f49fef8bc 100644
--- a/drivers/AnalogOut.h
+++ b/drivers/AnalogOut.h
@@ -141,7 +141,7 @@ public:
     }
 
 protected:
-
+    #if !defined(DOXYGEN_ONLY)
     virtual void lock()
     {
         _mutex.lock();
@@ -154,6 +154,7 @@ protected:
 
     dac_t _dac;
     PlatformMutex _mutex;
+    #endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed
diff --git a/drivers/DigitalIn.h b/drivers/DigitalIn.h
index 1a2af01fa3..a5679b1225 100644
--- a/drivers/DigitalIn.h
+++ b/drivers/DigitalIn.h
@@ -108,6 +108,11 @@ public:
 
     /** An operator shorthand for read()
      * \sa DigitalIn::read()
+     * @code
+     *      DigitalIn  button(BUTTON1);
+     *      DigitalOut led(LED1);
+     *      led = button;   // Equivalent to led.write(button.read())
+     * @endcode
      */
     operator int()
     {
@@ -116,7 +121,9 @@ public:
     }
 
 protected:
+    #if !defined(DOXYGEN_ONLY)
     gpio_t gpio;
+    #endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed
diff --git a/drivers/DigitalInOut.h b/drivers/DigitalInOut.h
index a11fcad2c0..74a5747f20 100644
--- a/drivers/DigitalInOut.h
+++ b/drivers/DigitalInOut.h
@@ -121,6 +121,13 @@ public:
 
     /** A shorthand for write()
      * \sa DigitalInOut::write()
+     * @code
+     *      DigitalInOut  inout(PIN);
+     *      DigitalIn     button(BUTTON1);
+     *      inout.output();
+     *
+     *      inout = button;     // Equivalent to inout.write(button.read())
+     * @endcode
      */
     DigitalInOut &operator= (int value)
     {
@@ -129,7 +136,8 @@ public:
         return *this;
     }
 
-    /** A shorthand for write()
+    /**A shorthand for write() using the assignment operator which copies the
+     * state from the DigitalInOut argument.
      * \sa DigitalInOut::write()
      */
     DigitalInOut &operator= (DigitalInOut &rhs)
@@ -142,6 +150,13 @@ public:
 
     /** A shorthand for read()
      * \sa DigitalInOut::read()
+     * @code
+     *      DigitalInOut inout(PIN);
+     *      DigitalOut led(LED1);
+     *
+     *      inout.input();
+     *      led = inout;   // Equivalent to led.write(inout.read())
+     * @endcode
      */
     operator int()
     {
@@ -150,7 +165,9 @@ public:
     }
 
 protected:
+    #if !defined(DOXYGEN_ONLY)
     gpio_t gpio;
+    #endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed
diff --git a/drivers/DigitalOut.h b/drivers/DigitalOut.h
index fb6d1be6c2..5758c2658c 100644
--- a/drivers/DigitalOut.h
+++ b/drivers/DigitalOut.h
@@ -104,6 +104,11 @@ public:
 
     /** A shorthand for write()
      * \sa DigitalOut::write()
+     * @code
+     *      DigitalIn  button(BUTTON1);
+     *      DigitalOut led(LED1);
+     *      led = button;   // Equivalent to led.write(button.read())
+     * @endcode
      */
     DigitalOut &operator= (int value)
     {
@@ -112,7 +117,8 @@ public:
         return *this;
     }
 
-    /** A shorthand for write()
+    /** A shorthand for write() using the assignment operator which copies the
+     * state from the DigitalOut argument.
      * \sa DigitalOut::write()
      */
     DigitalOut &operator= (DigitalOut &rhs)
@@ -125,6 +131,11 @@ public:
 
     /** A shorthand for read()
      * \sa DigitalOut::read()
+     * @code
+     *      DigitalIn  button(BUTTON1);
+     *      DigitalOut led(LED1);
+     *      led = button;   // Equivalent to led.write(button.read())
+     * @endcode
      */
     operator int()
     {
@@ -133,7 +144,9 @@ public:
     }
 
 protected:
+    #if !defined(DOXYGEN_ONLY)
     gpio_t gpio;
+    #endif //!defined(DOXYGEN_ONLY)
 };
 
 } // namespace mbed