diff --git a/examples/FunctionInterruptSimulation/FunctionInterruptSimulation.cpp b/examples/FunctionInterruptSimulation/FunctionInterruptSimulation.cpp
index d7fffbdf..186f4542 100644
--- a/examples/FunctionInterruptSimulation/FunctionInterruptSimulation.cpp
+++ b/examples/FunctionInterruptSimulation/FunctionInterruptSimulation.cpp
@@ -66,19 +66,11 @@ class Timer
 {
 public:
 
-  Timer(int interruptId)
-    : callback(*this)
-  {
-    GetInterruptVectorsInstance().register_callback(interruptId, callback);
-  }
-
   // Handler for interrupts from the timer.
   void InterruptHandler(const size_t id)
   {
     std::cout << "Timer interrupt (member) : ID " << id << "\n";
   }
-
-  etl::function_mp<Timer, size_t, &Timer::InterruptHandler> callback;
 };
 
 //********************************
@@ -121,10 +113,14 @@ void UnhandledInterrupt(const size_t id)
 }
 
 // Declare the driver instances.
-Timer timer(TIM1_CC_IRQ_HANDLER);
+Timer timer;
 Uart  uart1(0, USART1_IRQ_HANDLER);
 Uart  uart2(1, USART2_IRQ_HANDLER);
 
+// Declare a global callback for the timer.
+// Uses the most efficient callback type for a class, as everthing is known at compile time.
+etl::function_imp<Timer, size_t, timer, &Timer::InterruptHandler> timer_member_callback;
+
 // Declare the callbacks for the free functions.
 etl::function_fp<size_t, FreeTimerInterruptHandler> timer_free_callback;
 etl::function_fp<size_t, UnhandledInterrupt>        unhandled_callback;
@@ -137,6 +133,7 @@ int main()
   // Setup the callbacks.
   InterruptVectors& interruptVectors = GetInterruptVectorsInstance();
 
+  interruptVectors.register_callback<TIM1_CC_IRQ_HANDLER>(timer_member_callback);
   interruptVectors.register_callback<TIM2_IRQ_HANDLER>(timer_free_callback);
   interruptVectors.register_unhandled_callback(unhandled_callback);
 
diff --git a/include/etl/array_view.h b/include/etl/array_view.h
index ec46d96c..659a3a0e 100644
--- a/include/etl/array_view.h
+++ b/include/etl/array_view.h
@@ -114,7 +114,7 @@ namespace etl
     //*************************************************************************
     /// Default constructor.
     //*************************************************************************
-    array_view()
+    ETL_CONSTEXPR array_view()
       : mbegin(nullptr),
         mend(nullptr)
     {
@@ -125,7 +125,7 @@ namespace etl
     /// data() and size() member functions.
     //*************************************************************************
     template <typename TArray>
-    explicit array_view(TArray& a)
+    ETL_CONSTEXPR explicit array_view(TArray& a)
       : mbegin(a.data()),
         mend(a.data() + a.size())
     {
@@ -135,7 +135,7 @@ namespace etl
     /// Construct from iterators
     //*************************************************************************
     template <typename TIterator>
-    array_view(TIterator begin_, TIterator end_)
+    ETL_CONSTEXPR array_view(TIterator begin_, TIterator end_)
       : mbegin(etl::addressof(*begin_)),
         mend(etl::addressof(*begin_) + std::distance(begin_, end_))
     {
@@ -146,7 +146,7 @@ namespace etl
     //*************************************************************************
     template <typename TIterator, 
               typename TSize>
-    array_view(TIterator begin_, TSize size_)
+    ETL_CONSTEXPR array_view(TIterator begin_, TSize size_)
       : mbegin(etl::addressof(*begin_)),
         mend(etl::addressof(*begin_) + size_)
     {
@@ -156,7 +156,7 @@ namespace etl
     /// Construct from C array
     //*************************************************************************
     template<const size_t ARRAY_SIZE>
-    explicit array_view(T(&begin_)[ARRAY_SIZE])
+    ETL_CONSTEXPR explicit array_view(T(&begin_)[ARRAY_SIZE])
       : mbegin(begin_),
         mend(begin_ + ARRAY_SIZE)
     {
@@ -165,7 +165,7 @@ namespace etl
     //*************************************************************************
     /// Copy constructor
     //*************************************************************************
-    array_view(const array_view& other)
+    ETL_CONSTEXPR array_view(const array_view& other)
       : mbegin(other.mbegin),
         mend(other.mend)
     {
@@ -504,7 +504,7 @@ namespace etl
     //*************************************************************************
     /// Default constructor.
     //*************************************************************************
-    const_array_view()
+    ETL_CONSTEXPR const_array_view()
       : mbegin(nullptr),
         mend(nullptr)
     {
@@ -515,7 +515,7 @@ namespace etl
     /// data() and size() member functions.
     //*************************************************************************
     template <typename TArray>
-    explicit const_array_view(TArray& a)
+    ETL_CONSTEXPR explicit const_array_view(TArray& a)
       : mbegin(a.data()),
         mend(a.data() + a.size())
     {
@@ -525,7 +525,7 @@ namespace etl
     /// Construct from iterators
     //*************************************************************************
     template <typename TIterator>
-    const_array_view(TIterator begin_, TIterator end_)
+    ETL_CONSTEXPR const_array_view(TIterator begin_, TIterator end_)
       : mbegin(etl::addressof(*begin_)),
         mend(etl::addressof(*begin_) + std::distance(begin_, end_))
     {
@@ -536,7 +536,7 @@ namespace etl
     //*************************************************************************
     template <typename TIterator, 
               typename TSize>
-    const_array_view(TIterator begin_, TSize size_)
+    ETL_CONSTEXPR const_array_view(TIterator begin_, TSize size_)
       : mbegin(etl::addressof(*begin_)),
         mend(etl::addressof(*begin_) + size_)
     {
@@ -546,16 +546,16 @@ namespace etl
     /// Construct from C array
     //*************************************************************************
     template<const size_t ARRAY_SIZE>
-    explicit const_array_view(const T(&begin_)[ARRAY_SIZE])
+    ETL_CONSTEXPR explicit const_array_view(const T(&begin_)[ARRAY_SIZE])
       : mbegin(begin_),
         mend(begin_ + ARRAY_SIZE)
     {
     }
 
-    //*************************************************************************
+    //************0*************************************************************
     /// Copy constructor
     //*************************************************************************
-    const_array_view(const array_view<T>& other)
+    ETL_CONSTEXPR const_array_view(const array_view<T>& other)
       : mbegin(other.begin()),
         mend(other.end())
     {
@@ -564,9 +564,9 @@ namespace etl
     //*************************************************************************
     /// Copy constructor
     //*************************************************************************
-    const_array_view(const const_array_view& other)
+    ETL_CONSTEXPR const_array_view(const const_array_view& other)
       : mbegin(other.mbegin),
-      mend(other.mend)
+        mend(other.mend)
     {
     }
 
diff --git a/include/etl/string_view.h b/include/etl/string_view.h
index 39ccd7ff..d8247bb1 100644
--- a/include/etl/string_view.h
+++ b/include/etl/string_view.h
@@ -118,7 +118,7 @@ namespace etl
     //*************************************************************************
     /// Default constructor.
     //*************************************************************************
-    basic_string_view()
+    ETL_CONSTEXPR basic_string_view()
       : mbegin(nullptr),
         mend(nullptr)
     {
@@ -127,7 +127,7 @@ namespace etl
     //*************************************************************************
     /// Construct from T*.
     //*************************************************************************
-    basic_string_view(const T* begin_)
+    ETL_CONSTEXPR basic_string_view(const T* begin_)
       : mbegin(begin_),
         mend(begin_ + TTraits::length(begin_))
     {
@@ -136,7 +136,7 @@ namespace etl
     //*************************************************************************
     /// Construct from pointer range.
     //*************************************************************************
-    basic_string_view(const T* begin_, const T* end_)
+    ETL_CONSTEXPR basic_string_view(const T* begin_, const T* end_)
       : mbegin(begin_),
         mend(end_)
     {
@@ -146,7 +146,7 @@ namespace etl
     /// Construct from iterator/size.
     //*************************************************************************
     template <typename TSize, typename TDummy = typename etl::enable_if<etl::is_integral<TSize>::value, void>::type>
-    basic_string_view(const T* begin_, TSize size_)
+    ETL_CONSTEXPR basic_string_view(const T* begin_, TSize size_)
       : mbegin(begin_),
         mend(begin_ + size_)
     {
@@ -155,7 +155,7 @@ namespace etl
     //*************************************************************************
     /// Copy constructor
     //*************************************************************************
-    basic_string_view(const basic_string_view& other)
+    ETL_CONSTEXPR basic_string_view(const basic_string_view& other)
       : mbegin(other.mbegin),
         mend(other.mend)
     {
diff --git a/include/etl/version.h b/include/etl/version.h
index 8d74618f..97efaef9 100644
--- a/include/etl/version.h
+++ b/include/etl/version.h
@@ -38,8 +38,8 @@ SOFTWARE.
 ///\ingroup utilities
 
 #define ETL_VERSION_MAJOR 14
-#define ETL_VERSION_MINOR  8
-#define ETL_VERSION_PATCH  2
+#define ETL_VERSION_MINOR  9
+#define ETL_VERSION_PATCH  0
 
 #define ETL_VERSION       ETL_STRINGIFY(ETL_VERSION_MAJOR) ETL_STRINGIFY(ETL_VERSION_MINOR) ETL_STRINGIFY(ETL_VERSION_PATCH)
 #define ETL_VERSION_W     ETL_WIDE_STRING(ETL_CONCAT(ETL_CONCAT(ETL_VERSION_MAJOR, ETL_VERSION_MINOR), ETL_VERSION_PATCH))
diff --git a/support/Release notes.txt b/support/Release notes.txt
index c50fdd8b..3db09549 100644
--- a/support/Release notes.txt	
+++ b/support/Release notes.txt	
@@ -1,3 +1,7 @@
+===============================================================================
+14.9.0
+Added constexpr constructors to string_view and array_view.
+
 ===============================================================================
 14.8.2
 Added missing #include "stl/interator.h" in frame_check_sequence.h