diff --git a/libraries/mbed/common/pinmap_common.c b/libraries/mbed/common/pinmap_common.c
index eef617fd45..3dc4433176 100644
--- a/libraries/mbed/common/pinmap_common.c
+++ b/libraries/mbed/common/pinmap_common.c
@@ -17,7 +17,8 @@
 #include "error.h"
 
 void pinmap_pinout(PinName pin, const PinMap *map) {
-    if (pin == NC) return;
+    if (pin == NC)
+        return;
 
     while (map->pin != NC) {
         if (map->pin == pin) {
@@ -33,11 +34,14 @@ void pinmap_pinout(PinName pin, const PinMap *map) {
 
 uint32_t pinmap_merge(uint32_t a, uint32_t b) {
     // both are the same (inc both NC)
-    if (a == b) return a;
+    if (a == b)
+        return a;
 
     // one (or both) is not connected
-    if (a == (uint32_t)NC) return b;
-    if (b == (uint32_t)NC) return a;
+    if (a == (uint32_t)NC)
+        return b;
+    if (b == (uint32_t)NC)
+        return a;
 
     // mis-match error case
     error("pinmap mis-match");
diff --git a/libraries/mbed/common/retarget.cpp b/libraries/mbed/common/retarget.cpp
index 35a815916c..cfc3f1d274 100644
--- a/libraries/mbed/common/retarget.cpp
+++ b/libraries/mbed/common/retarget.cpp
@@ -396,6 +396,13 @@ extern "C" WEAK void __cxa_pure_virtual(void) {
 
 #endif
 
+#include "mbed_interface.h"
+
+extern "C" void abort(void) {
+    mbed_die();
+    while(1);
+}
+
 // ****************************************************************************
 // mbed_main is a function that is called before main()
 // mbed_sdk_init() is also a function that is called before main(), but unlike
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_api.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_api.c
index 5daf354974..70671ed002 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_api.c
@@ -13,19 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     pin_function(pin, 1);
     return 1 << ((pin & 0x7F) >> 2);
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
-    if(pin == (PinName)NC)
+    obj->pin = pin;
+    if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
 
     unsigned int port = (unsigned int)pin >> PORT_SHIFT;
@@ -42,9 +44,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_object.h b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_object.h
index cd9e6608f9..35923ebd1f 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -41,8 +42,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/pinmap.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/pinmap.c
index 9adef24d09..a7a0be9297 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_K20D5M/pinmap.c
@@ -13,12 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
-#include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC)
-        return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_n = (uint32_t)pin >> PORT_SHIFT;
     uint32_t pin_n  = (uint32_t)(pin & 0x7C) >> 2;
@@ -31,8 +30,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
-
+    assert(pin != (PinName)NC);
     __IO uint32_t* pin_pcr = (__IO uint32_t*)(PORTA_BASE + pin);
 
     // pin pullup bits: [1:0] -> 11 = (0x3)
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_api.c
index bdcb54cbcc..add01e1216 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_api.c
@@ -13,19 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     pin_function(pin, 1);
     return 1 << ((pin & 0x7F) >> 2);
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
 
     unsigned int port = (unsigned int)pin >> PORT_SHIFT;
@@ -42,9 +44,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_object.h
index bde8b15256..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -40,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/pinmap.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/pinmap.c
index 9efe64843d..36ff078d93 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KLXX/pinmap.c
@@ -13,12 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
-#include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC)
-        return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_n = (uint32_t)pin >> PORT_SHIFT;
     uint32_t pin_n  = (uint32_t)(pin & 0x7C) >> 2;
@@ -31,8 +30,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC)
-        return;
+    assert(pin != (PinName)NC);
 
     __IO uint32_t* pin_pcr = (__IO uint32_t*)(PORTA_BASE + pin);
 
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_api.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_api.c
index e9fa1fa86d..909bd6198d 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_api.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "fsl_port_hal.h"
@@ -20,6 +21,7 @@
 #include "fsl_sim_hal.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     uint32_t pin_num = pin & 0xFF;
 
     pin_function(pin, (int)kPortMuxAsGpio);
@@ -27,10 +29,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pinName = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pinName = pin;
     uint32_t port = pin >> GPIO_PORT_SHIFT;
     uint32_t pin_num = pin & 0xFF;
     clock_hal_set_gate(kSimClockModulePORT, port, true);
@@ -42,8 +44,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pinName != (PinName)NC);
     uint32_t port = obj->pinName >> GPIO_PORT_SHIFT;
     uint32_t pin_num = obj->pinName & 0xFF;
 
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_object.h b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_object.h
index 6a5189040a..94db08ea1e 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/gpio_object.h
@@ -16,6 +16,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "fsl_gpio_hal.h"
 
 #ifdef __cplusplus
@@ -27,8 +28,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pinName != (PinName)NC);
     uint32_t port = obj->pinName >> GPIO_PORT_SHIFT;
     uint32_t pin = obj->pinName & 0xFF;
 
@@ -36,8 +36,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pinName != (PinName)NC);
     uint32_t port = obj->pinName >> GPIO_PORT_SHIFT;
     uint32_t pin = obj->pinName & 0xFF;
 
diff --git a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/pinmap.c b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/pinmap.c
index f03db67a9f..db0b212baf 100644
--- a/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KPSDK_MCUS/TARGET_K64F/pinmap.c
@@ -13,25 +13,20 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 #include "fsl_clock_manager.h"
 #include "fsl_port_hal.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC) {
-        return;
-    }
-
+    assert(pin != (PinName)NC);
     clock_manager_set_gate(kClockModulePORT, pin >> GPIO_PORT_SHIFT, true);
     port_hal_mux_control(pin >> GPIO_PORT_SHIFT, pin & 0xFF, (port_mux_t)function);
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) {
-        return;
-    }
-
+    assert(pin != (PinName)NC);
     uint32_t instance = pin >> GPIO_PORT_SHIFT;
     uint32_t pinName = pin & 0xFF;
 
diff --git a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_api.c
index b79bd6eb2b..82bece68fd 100644
--- a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_api.c
@@ -13,14 +13,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 void gpio_init(gpio_t *obj, PinName pin) {
-    if(pin == (PinName)NC)
+    obj->pin = pin;
+    if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = (1ul << pin);
 
     obj->reg_set = &NRF_GPIO->OUTSET;
@@ -34,22 +35,21 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
-        NRF_GPIO->PIN_CNF[obj->pin] = (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
+            NRF_GPIO->PIN_CNF[obj->pin] = (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
                                         | (GPIO_PIN_CNF_DRIVE_S0S1 << GPIO_PIN_CNF_DRIVE_Pos)
                                         | (GPIO_PIN_CNF_INPUT_Connect << GPIO_PIN_CNF_INPUT_Pos)
                                         | (GPIO_PIN_CNF_DIR_Input << GPIO_PIN_CNF_DIR_Pos);
-                                        break;
+            break;
         case PIN_OUTPUT:
-        NRF_GPIO->PIN_CNF[obj->pin] = (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
+            NRF_GPIO->PIN_CNF[obj->pin] = (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
                                         | (GPIO_PIN_CNF_DRIVE_S0S1 << GPIO_PIN_CNF_DRIVE_Pos)
                                         | (GPIO_PIN_CNF_PULL_Disabled << GPIO_PIN_CNF_PULL_Pos)
                                         | (GPIO_PIN_CNF_INPUT_Connect << GPIO_PIN_CNF_INPUT_Pos)
                                         | (GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos);
-                                        break;
+            break;
     }
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_object.h
index bde8b15256..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -40,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/pinmap.c b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/pinmap.c
index 2c63ac2fa3..3a9eb37545 100644
--- a/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NORDIC/TARGET_NRF51822/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -20,10 +21,10 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
+    assert(pin != (PinName)NC);
     
     uint32_t pin_number = (uint32_t)pin;
     
     NRF_GPIO->PIN_CNF[pin_number] &= ~GPIO_PIN_CNF_PULL_Msk;
-    NRF_GPIO->PIN_CNF[pin_number] |= (mode<<GPIO_PIN_CNF_PULL_Pos);
+    NRF_GPIO->PIN_CNF[pin_number] |= (mode << GPIO_PIN_CNF_PULL_Pos);
 }
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_api.c
index 89003d7dc4..0361f2b99f 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_api.c
@@ -13,20 +13,22 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     /* Enable AHB clock to the GPIO and IOCON domain. */
     LPC_SYSCON->SYSAHBCLKCTRL |= ((1 << 16) | (1 << 6));
     return (1UL << ((int)pin >> PIN_SHIFT & 0x1F));
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     unsigned int port = (unsigned int)(pin >> PORT_SHIFT);
@@ -42,9 +44,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_object.h
index f458edb9b5..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,9 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/pinmap.c
index d6628be206..8142396fc0 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11U6X/pinmap.c
@@ -13,15 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (uint32_t)NC)
-    {
-        return;
-    }
-
+    assert(pin != (PinName)NC);
     __IO uint32_t *reg = (__IO uint32_t*)(LPC_IOCON_BASE + (pin & 0x1FF));
 
     // pin function bits: [2:0] -> 111 = (0x7)
@@ -29,11 +26,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC)
-    {
-        return;
-    }
-    
+    assert(pin != (PinName)NC);
     if ((pin == P0_4) || (pin == P0_5)) {
         // The true open-drain pins PIO0_4 and PIO0_5 can be configured for different I2C-bus speeds.
         return;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_api.c
index 0026dfe4ca..00ae42d82a 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_api.c
@@ -13,10 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     int f = ((pin == P0_11) || (pin == P0_12) ||
              (pin == P0_13) || (pin == P0_14)) ? (1) : (0);
     pin_function(pin, f);
@@ -25,10 +27,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     unsigned int port = (unsigned int)pin >> PORT_SHIFT;
@@ -44,9 +46,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_object.h
index afef5d0f46..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,9 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,9 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (pin == (PinName)NC)
-        return 0;
-
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pinmap.c
index d7a157a1df..c431a9a12e 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11UXX/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -20,27 +21,27 @@
 #define LPC_IOCON1_BASE (LPC_IOCON_BASE + 0x60)
 
 void pin_function(PinName pin, int function) {
+    assert(pin != (PinName)NC);
     if (pin == (PinName)NC) return;
     
     uint32_t pin_number = (uint32_t)pin;
     
     __IO uint32_t *reg = (pin_number < 32) ?
-            (__IO uint32_t*)(LPC_IOCON0_BASE + 4 * pin_number) :
-            (__IO uint32_t*)(LPC_IOCON1_BASE + 4 * (pin_number - 32));
+                         (__IO uint32_t*)(LPC_IOCON0_BASE + 4 * pin_number) :
+                         (__IO uint32_t*)(LPC_IOCON1_BASE + 4 * (pin_number - 32));
     
     // pin function bits: [2:0] -> 111 = (0x7)
     *reg = (*reg & ~0x7) | (function & 0x7);
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
-    
+    assert(pin != (PinName)NC);
     uint32_t pin_number = (uint32_t)pin;
     uint32_t drain = ((uint32_t) mode & (uint32_t) OpenDrain) >> 2;
     
     __IO uint32_t *reg = (pin_number < 32) ?
-            (__IO uint32_t*)(LPC_IOCON0_BASE + 4 * pin_number) :
-            (__IO uint32_t*)(LPC_IOCON1_BASE + 4 * (pin_number - 32));
+                         (__IO uint32_t*)(LPC_IOCON0_BASE + 4 * pin_number) :
+                         (__IO uint32_t*)(LPC_IOCON1_BASE + 4 * (pin_number - 32));
     uint32_t tmp = *reg;
     
     // pin mode bits: [4:3] -> 11000 = (0x3 << 3)
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_api.c
index f91ae52f8e..b695978ea1 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_api.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "reserved_pins.h"
@@ -20,25 +21,26 @@
 static const PinName reserved_pins[] = TARGET_RESERVED_PINS;
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     // PIO default value of following ports are not same as others
     unsigned i;
     int f = 0;
 
-    for (i = 0; i < sizeof(reserved_pins) / sizeof(PinName); i ++)
+    for (i = 0; i < sizeof(reserved_pins) / sizeof(PinName); i ++) {
         if (pin == reserved_pins[i]) {
             f = 1;
             break;
         }
-   
+    }
     pin_function(pin, f);
     return ((pin & 0x0F00) >> 8);
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     LPC_GPIO_TypeDef *port_reg = ((LPC_GPIO_TypeDef *) (LPC_GPIO0_BASE + (((pin & 0xF000) >> PORT_SHIFT) * 0x10000)));
 
     obj->reg_mask_read = &port_reg->MASKED_ACCESS[1 << gpio_set(pin)];
@@ -51,12 +53,14 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     int pin_number = ((obj->pin & 0x0F00) >> 8);
     switch (direction) {
-        case PIN_INPUT : *obj->reg_dir &= ~(1 << pin_number); break;
-        case PIN_OUTPUT: *obj->reg_dir |=  (1 << pin_number); break;
+        case PIN_INPUT :
+            *obj->reg_dir &= ~(1 << pin_number);
+            break;
+        case PIN_OUTPUT:
+            *obj->reg_dir |= (1 << pin_number);
+            break;
     }
 }
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_object.h
index ccac8dce10..71a8ce10e2 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -28,8 +30,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     uint32_t pin_number = ((obj->pin & 0x0F00) >> 8);
     if (value)
         *obj->reg_write |= (1 << pin_number);
@@ -38,8 +39,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_mask_read) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pinmap.c
index 8006ca18f1..a20eba6e02 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pinmap.c
@@ -13,12 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (uint32_t)NC) return;
-    
+    assert(pin != (PinName)NC);
     uint32_t offset = (uint32_t)pin & 0xff;
     __IO uint32_t *reg = (__IO uint32_t*)(LPC_IOCON_BASE + offset);
 
@@ -27,10 +27,9 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
-    
+    assert(pin != (PinName)NC);
     uint32_t offset = (uint32_t)pin & 0xff;
-    uint32_t drain = ((uint32_t) mode & (uint32_t) OpenDrain) >> 2;
+    uint32_t drain = ((uint32_t)mode & (uint32_t)OpenDrain) >> 2;
     
     __IO uint32_t *reg = (__IO uint32_t*)(LPC_IOCON_BASE + offset);
     uint32_t tmp = *reg;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_api.c
index acdd9aceab..09f67a6cb2 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_api.c
@@ -13,10 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     int f = ((pin == P0_11) || (pin == P0_12) ||
              (pin == P0_13) || (pin == P0_14)) ? (1) : (0);
     pin_function(pin, f);
@@ -25,10 +27,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     unsigned int port = (unsigned int)pin >> PORT_SHIFT;
@@ -44,10 +46,13 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
-        case PIN_INPUT : *obj->reg_dir &= ~obj->mask; break;
-        case PIN_OUTPUT: *obj->reg_dir |=  obj->mask; break;
+        case PIN_INPUT :
+            *obj->reg_dir &= ~obj->mask;
+            break;
+        case PIN_OUTPUT:
+            *obj->reg_dir |= obj->mask;
+            break;
     }
 }
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_object.h
index bde8b15256..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -40,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/pinmap.c
index 4e2445c658..c28c675938 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -20,7 +21,7 @@
 #define LPC_IOCON1_BASE (LPC_IOCON_BASE + 0x60)
 
 void pin_function(PinName pin, int function) {
-    if (pin == (uint32_t)NC) return;
+    assert(pin != (PinName)NC);
     
     uint32_t pin_number = (uint32_t)pin;
     
@@ -33,7 +34,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
+    assert(pin != (PinName)NC);
     
     uint32_t pin_number = (uint32_t)pin;
     uint32_t drain = ((uint32_t) mode & (uint32_t) OpenDrain) >> 2;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_api.c
index 6e7a378444..94479a4359 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_api.c
@@ -13,19 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     LPC_SYSCON->SYSAHBCLKCTRL0 |= (0xFUL << 13);
     return (1UL << ((int)pin & 0x1f));
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     unsigned int port = (unsigned int)(pin >> 5);
@@ -41,9 +43,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_object.h
index f458edb9b5..b0eabec850 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
 
     if (value)
         *obj->reg_set = obj->mask;
@@ -41,8 +42,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/pinmap.c
index d39c6912dc..5592282829 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC15XX/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -20,7 +21,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
+    assert(pin != (PinName)NC);
     
     if ((pin == P0_22) || (pin == P0_23)) {
         // The true open-drain pins PIO0_22 and PIO0_23 can be configured for different I2C-bus speeds.
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_api.c
index 5bbfca3778..dd34db71da 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_api.c
@@ -13,21 +13,23 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     pin_function(pin, 0);
     return (1 << ((int)pin & 0x1F));
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
-    obj->pin = pin;
+
     obj->mask = gpio_set(pin);
-    
-    LPC_GPIO_TypeDef *port_reg = (LPC_GPIO_TypeDef *) ((int)pin & ~0x1F);
+    LPC_GPIO_TypeDef *port_reg = (LPC_GPIO_TypeDef *)((int)pin & ~0x1F);
     obj->reg_set = &port_reg->FIOSET;
     obj->reg_clr = &port_reg->FIOCLR;
     obj->reg_in  = &port_reg->FIOPIN;
@@ -39,10 +41,13 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
-        case PIN_INPUT : *obj->reg_dir &= ~obj->mask; break;
-        case PIN_OUTPUT: *obj->reg_dir |=  obj->mask; break;
+        case PIN_INPUT :
+            *obj->reg_dir &= ~obj->mask;
+            break;
+        case PIN_OUTPUT:
+            *obj->reg_dir |= obj->mask;
+            break;
     }
 }
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_object.h
index bde8b15256..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -40,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/pinmap.c
index be017ce181..1600a5fe5d 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/pinmap.c
@@ -13,12 +13,13 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC) return;
-    
+    assert(pin != (PinName)NC);
+
     uint32_t pin_number = (uint32_t)pin - (uint32_t)P0_0;
     int index = pin_number >> 4;
     int offset = (pin_number & 0xF) << 1;
@@ -28,7 +29,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
+    assert(pin != (PinName)NC);
     
     uint32_t pin_number = (uint32_t)pin - (uint32_t)P0_0;
     int index = pin_number >> 5;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_api.c
index 1e9ef6e99c..ada9c74615 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_api.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_object.h
index bde8b15256..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,8 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -40,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/pinmap.c
index 84173661c9..ef1ed3752c 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC23XX/pinmap.c
@@ -13,11 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC) return;
+    assert(pin != (PinName)NC);
     
     uint32_t pin_number = (uint32_t)pin - (uint32_t)P0_0;
     int index = pin_number >> 4;
@@ -28,15 +29,13 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
-    
+    assert((pin != (PinName)NC) && (mode != OpenDrain));
+
     uint32_t pin_number = (uint32_t)pin - (uint32_t)P0_0;
     int index = pin_number >> 5;
     int offset = pin_number & 0x1F;
     uint32_t drain = ((uint32_t) mode & (uint32_t) OpenDrain) >> 2;
-    
-    if (mode == OpenDrain) error("OpenDrain not supported on LPC2368");
-    
+
     if (!drain) {
         index = pin_number >> 4;
         offset = (pin_number & 0xF) << 1;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_api.c
index 1b79dbdbf4..012b5b256b 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_api.c
@@ -13,19 +13,21 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     pin_function(pin, 0);
     return (1 << ((int)pin & 0x1F));
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     LPC_GPIO_TypeDef *port_reg = (LPC_GPIO_TypeDef *) ((int)(LPC_GPIO0_BASE+pin) & ~0x1F);
@@ -41,8 +43,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
 
     switch (direction) {
         case PIN_INPUT :
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_object.h
index f458edb9b5..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,9 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/pinmap.c
index d2e277ba9e..6b3a49defb 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC408X/pinmap.c
@@ -13,12 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (PinName)NC) return;
-    
+    assert(pin != (PinName)NC);
     __IO uint32_t *reg = (__IO uint32_t*) (LPC_IOCON_BASE + 4 * pin);
     
     // pin function bits: [2:0] -> 111 = (0x7)
@@ -26,7 +26,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (PinName)NC) { return; }
+    assert(pin != (PinName)NC);
     
     uint32_t drain = ((uint32_t) mode & (uint32_t) OpenDrain) >> 2;
     
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_api.c
index 8ec9895b14..c2706befd9 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_api.c
@@ -15,10 +15,12 @@
  *
  * Ported to NXP LPC43XX by Micromint USA <support@micromint.com>
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     int f = 0;
     unsigned int port = (unsigned int)MBED_GPIO_PORT(pin);
 
@@ -29,10 +31,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
 
     LPC_GPIO_T *port_reg = (LPC_GPIO_T *) (LPC_GPIO_PORT_BASE);
@@ -49,11 +51,13 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
-        case PIN_INPUT : *obj->reg_dir &= ~obj->mask; break;
-        case PIN_OUTPUT: *obj->reg_dir |=  obj->mask; break;
+        case PIN_INPUT :
+            *obj->reg_dir &= ~obj->mask;
+            break;
+        case PIN_OUTPUT:
+            *obj->reg_dir |=  obj->mask;
+            break;
     }
 }
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_object.h
index f458edb9b5..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,9 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,8 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/pinmap.c
index f55ec37505..14a04f27e8 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC43XX/pinmap.c
@@ -15,11 +15,12 @@
  *
  * Ported to NXP LPC43XX by Micromint USA <support@micromint.com>
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
 void pin_function(PinName pin, int function) {
-    if (pin == (uint32_t)NC) return;
+    assert(pin != (PinName)NC);
 
     __IO uint32_t *reg = (__IO uint32_t*) MBED_SCU_REG(pin);
 
@@ -28,9 +29,7 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
-
-    if (mode == OpenDrain) error("OpenDrain not supported on LPC43XX");
+    assert((pin != (PinName)NC) && (mode == OpenDrain));
 
     __IO uint32_t *reg = (__IO uint32_t*) MBED_SCU_REG(pin);
     uint32_t tmp = *reg;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_api.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_api.c
index 7abd786d68..06e311fe5e 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_api.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
@@ -40,10 +41,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
     
     obj->reg_set = &LPC_GPIO_PORT->SET0;
@@ -57,9 +58,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             *obj->reg_dir &= ~obj->mask;
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_object.h b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_object.h
index 0688da0ab9..e6bb82e4d4 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -31,9 +33,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,9 +41,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
-
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pinmap.c b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pinmap.c
index d8ac966d46..0a3c9be761 100644
--- a/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -30,8 +31,8 @@ void pin_function(PinName pin, int function) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
-    
+    assert(pin != (PinName)NC);
+
     if ((pin == 10) || (pin == 11)) {
         // True open-drain pins can be configured for different I2C-bus speeds
         return;
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_api.c
index 24bd4d7866..bcaf274239 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
     
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     }
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_object.h
index 627efff9d0..9a5b49c92a 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,9 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     }
@@ -60,8 +59,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/pinmap.c
index 3f2812695e..cfe5388bdb 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F051R8/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "device.h"
 #include "pinmap.h"
 #include "error.h"
@@ -66,8 +67,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t otype = STM_PIN_OTYPE(data);
@@ -104,15 +104,14 @@ void pin_function(PinName pin, int data) {
     //}
     //if ((pin == PA_15) || (pin == PB_3) || (pin == PB_4)) {
     //
-    //}    
+    //}
 }
 
 /**
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -122,7 +121,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
     
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_api.c
index a58e4faf6f..72ca82b0de 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN_FLOATING, 0));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
     
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_Out_PP, 0));
     }
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_object.h
index e784f466b4..f338e08ae9 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/pinmap.c
index e82f85b1cc..3cc0ca7db5 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F100RB/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "device.h"
 #include "pinmap.h"
 #include "error.h"
@@ -75,8 +76,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (input, output, alternate function or analog) + output speed + AF
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t afnum = STM_PIN_AFNUM(data);
@@ -111,17 +111,16 @@ void pin_function(PinName pin, int data) {
     }
     if ((pin == PA_15) || (pin == PB_3) || (pin == PB_4)) {
         GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE);
-    }    
+    }
 }
 
 /**
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
+    assert(pin != (PinName)NC);
     GPIO_InitTypeDef GPIO_InitStructure;
     
-    if (pin == NC) return;
-
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -131,32 +130,31 @@ void pin_mode(PinName pin, PinMode mode) {
   
     // Configure open-drain and pull-up/down
     switch (mode) {
-      case PullNone:       
-        return;
-      case PullUp:
-        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
-      break;
-      case PullDown:
-        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;
-      break;
-      case OpenDrain:
-        if (pin_index < 8) {
-            if ((gpio->CRL & (0x03 << (pin_index * 4))) > 0) { // MODE bits = Output mode
-                gpio->CRL |= (0x04 << (pin_index * 4)); // Set open-drain
+        case PullNone:
+            return;
+        case PullUp:
+            GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
+            break;
+        case PullDown:
+            GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;
+            break;
+        case OpenDrain:
+            if (pin_index < 8) {
+                if ((gpio->CRL & (0x03 << (pin_index * 4))) > 0) { // MODE bits = Output mode
+                    gpio->CRL |= (0x04 << (pin_index * 4)); // Set open-drain
+                }
+            } else {
+                if ((gpio->CRH & (0x03 << ((pin_index % 8) * 4))) > 0) { // MODE bits = Output mode
+                    gpio->CRH |= (0x04 << ((pin_index % 8) * 4)); // Set open-drain
+                }
             }
-        }
-        else {
-            if ((gpio->CRH & (0x03 << ((pin_index % 8) * 4))) > 0) { // MODE bits = Output mode          
-                gpio->CRH |= (0x04 << ((pin_index % 8) * 4)); // Set open-drain
-            }
-        }
-        return;
-      default:
-      break;
+            return;
+        default:
+            break;
     }
     
     // Configure GPIO
     GPIO_InitStructure.GPIO_Pin   = (uint16_t)(1 << pin_index);
     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
-    GPIO_Init(gpio, &GPIO_InitStructure);    
+    GPIO_Init(gpio, &GPIO_InitStructure);
 }
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_api.c
index 18ca26de89..7b80aecca5 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_object.h
index 15515cfeac..65d1f43622 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,9 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -59,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/pinmap.c
index 65addc0801..5dca9319e5 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F303VC/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "device.h"
 #include "pinmap.h"
 #include "error.h"
@@ -71,7 +72,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
@@ -108,14 +109,14 @@ void pin_function(PinName pin, int data) {
     //}
     //if ((pin == PA_15) || (pin == PB_3) || (pin == PB_4)) {
     //
-    //}    
+    //}
 }
 
 /**
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
@@ -126,7 +127,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
     
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_api.c
index 1b4497ecc7..cd9a69092e 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -35,14 +36,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(STM_MODE_INPUT, GPIO_NOPULL, 0));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
     uint32_t port_index = STM_PORT(pin);
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
     
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRRL;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(STM_MODE_OUTPUT_PP, GPIO_NOPULL, 0));
     }
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_object.h
index c8cf0aa398..8b3f175963 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     }
@@ -59,8 +59,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/pinmap.c
index b88ddeda79..1627bc6aaa 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_DISCO_F407VG/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "device.h"
 #include "pinmap.h"
 #include "error.h"
@@ -74,7 +75,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
             break;
         default:
             error("Pinmap error: wrong port number.");
-            break;          
+            break;
     }
     return gpio_add;
 }
@@ -83,8 +84,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t pupd  = STM_PIN_PUPD(data);
@@ -113,15 +113,14 @@ void pin_function(PinName pin, int data) {
     //}
     //if ((pin == PA_15) || (pin == PB_3) || (pin == PB_4)) {
     //
-    //}    
+    //}
 }
 
 /**
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -131,7 +130,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
     
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_api.c
index 24bd4d7866..1810771f82 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
     
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     }
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_object.h
index fde4b94296..9a5b49c92a 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     }
@@ -59,8 +59,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/pinmap.c
index c4f21316b1..dae9a3bfc7 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F030R8/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -66,7 +67,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
@@ -104,14 +105,14 @@ void pin_function(PinName pin, int data) {
     //}
     //if ((pin == PA_15) || (pin == PB_3) || (pin == PB_4)) {
     //
-    //}    
+    //}
 }
 
 /**
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_api.c
index 2babb7a67f..9c388a98f8 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN_FLOATING, 0));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_Out_PP, 0));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_object.h
index 4bad4fcb3f..c92e88ec3d 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -58,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/pinmap.c
index 58b6de14f3..edb828259d 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F103RB/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -77,8 +78,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (input, output, alternate function or analog) + output speed + AF
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t afnum = STM_PIN_AFNUM(data);
@@ -120,10 +120,9 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
+    assert(pin != (PinName)NC);
     GPIO_InitTypeDef GPIO_InitStructure;
 
-    if (pin == NC) return;
-
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_api.c
index 18ca26de89..7b80aecca5 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_object.h
index 15515cfeac..65d1f43622 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,9 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -59,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/pinmap.c
index 3cd9a2103a..05720d7568 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F302R8/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -67,8 +68,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t otype = STM_PIN_OTYPE(data);
@@ -111,8 +111,7 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -122,7 +121,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_api.c
index 2f44517db2..606f35d293 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(STM_MODE_INPUT, GPIO_NOPULL, 0));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRRL;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(STM_MODE_OUTPUT_PP, GPIO_NOPULL, 0));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_object.h
index 8a258bee05..26e9150df1 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -58,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/pinmap.c
index 53fe5ab305..280b5d2757 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_F401RE/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -82,8 +83,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t pupd  = STM_PIN_PUPD(data);
@@ -119,8 +119,7 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -130,7 +129,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_api.c
index ceb238d89d..87eb705842 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(STM_MODE_INPUT, GPIO_NOPULL, 0));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -52,7 +53,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -64,6 +64,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(STM_MODE_OUTPUT_PP, GPIO_NOPULL, 0));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_object.h
index 15515cfeac..65d1f43622 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,9 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
-
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -59,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/pinmap.c
index 5024f4ba7a..b58c7ceb61 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L053R8/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -82,8 +83,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
     uint32_t pupd  = STM_PIN_PUPD(data);
@@ -119,8 +119,7 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
-
+    assert(pin != (PinName)NC);
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
 
@@ -130,7 +129,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPD0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_api.c
index 059cc68b97..d106d3cc23 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,14 +35,14 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
     return (uint32_t)(1 << ((uint32_t)pin & 0xF)); // Return the pin mask
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
     uint32_t port_index = STM_PORT(pin);
@@ -51,7 +52,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRRL;
@@ -63,6 +63,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_object.h
index c1cb3a8b88..0e41836794 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -58,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/pinmap.c
index 715f165286..3d1e396579 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_NUCLEO_L152RE/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -66,7 +67,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
@@ -110,7 +111,7 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
@@ -121,7 +122,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_api.c
index 9a3a6705c6..6ed13d35b0 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_api.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 #include "error.h"
@@ -34,8 +35,7 @@
 extern uint32_t Set_GPIO_Clock(uint32_t port_idx);
 
 uint32_t gpio_set(PinName pin) {
-    if (pin == (PinName)NC)
-        return 0;
+    assert(pin != (PinName)NC);
 
     pin_function(pin, STM_PIN_DATA(GPIO_Mode_IN, 0, GPIO_PuPd_NOPULL, 0xFF));
 
@@ -43,6 +43,7 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
@@ -53,7 +54,6 @@ void gpio_init(gpio_t *obj, PinName pin) {
     GPIO_TypeDef *gpio = (GPIO_TypeDef *)gpio_add;
 
     // Fill GPIO object structure for future use
-    obj->pin     = pin;
     obj->mask    = gpio_set(pin);
     obj->reg_in  = &gpio->IDR;
     obj->reg_set = &gpio->BSRR;
@@ -65,6 +65,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     if (direction == PIN_OUTPUT) {
         pin_function(obj->pin, STM_PIN_DATA(GPIO_Mode_OUT, GPIO_OType_PP, GPIO_PuPd_NOPULL, 0xFF));
     } else { // PIN_INPUT
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_object.h
index 504b3c012b..65d1f43622 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/gpio_object.h
@@ -30,6 +30,7 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
 #include "cmsis.h"
 #include "PortNames.h"
 #include "PeripheralNames.h"
@@ -48,8 +49,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value) {
         *obj->reg_set = obj->mask;
     } else {
@@ -58,8 +58,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/pinmap.c
index d446e5f2c5..841b3a5517 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F3XX/pinmap.c
@@ -27,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *******************************************************************************
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "PortNames.h"
 #include "error.h"
@@ -71,7 +72,7 @@ uint32_t Set_GPIO_Clock(uint32_t port_idx) {
  * Configure pin (mode, speed, output type and pull-up/pull-down)
  */
 void pin_function(PinName pin, int data) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     // Get the pin informations
     uint32_t mode  = STM_PIN_MODE(data);
@@ -115,7 +116,7 @@ void pin_function(PinName pin, int data) {
  * Configure pin pull-up/pull-down
  */
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == NC) return;
+    assert(pin != (PinName)NC);
 
     uint32_t port_index = STM_PORT(pin);
     uint32_t pin_index  = STM_PIN(pin);
@@ -126,7 +127,8 @@ void pin_mode(PinName pin, PinMode mode) {
 
     // Configure pull-up/pull-down resistors
     uint32_t pupd = (uint32_t)mode;
-    if (pupd > 2) pupd = 0; // Open-drain = No pull-up/No pull-down
+    if (pupd > 2)
+        pupd = 0; // Open-drain = No pull-up/No pull-down
     gpio->PUPDR &= (uint32_t)(~(GPIO_PUPDR_PUPDR0 << (pin_index * 2)));
     gpio->PUPDR |= (uint32_t)(pupd << (pin_index * 2));
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_api.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_api.c
index 768e9e7bba..6d33fc4ec3 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_api.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_api.c
@@ -13,10 +13,12 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "gpio_api.h"
 #include "pinmap.h"
 
 uint32_t gpio_set(PinName pin) {
+    assert(pin != (PinName)NC);
     uint32_t port_index = (uint32_t) pin >> 4;
 
     // Enable GPIO peripheral clock
@@ -27,10 +29,10 @@ uint32_t gpio_set(PinName pin) {
 }
 
 void gpio_init(gpio_t *obj, PinName pin) {
+    obj->pin = pin;
     if (pin == (PinName)NC)
         return;
 
-    obj->pin = pin;
     obj->mask = gpio_set(pin);
 
     uint32_t port_index = (uint32_t) pin >> 4;
@@ -47,6 +49,7 @@ void gpio_mode(gpio_t *obj, PinMode mode) {
 }
 
 void gpio_dir(gpio_t *obj, PinDirection direction) {
+    assert(obj->pin != (PinName)NC);
     switch (direction) {
         case PIN_INPUT :
             pin_function(obj->pin, STM_PIN_DATA(0, 0));
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_object.h b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_object.h
index 23c6ad8e51..4b7855ecd6 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_object.h
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/gpio_object.h
@@ -16,6 +16,8 @@
 #ifndef MBED_GPIO_OBJECT_H
 #define MBED_GPIO_OBJECT_H
 
+#include <assert.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -32,8 +34,7 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (obj->pin == (PinName)NC)
-        return;
+    assert(obj->pin != (PinName)NC);
     if (value)
         *obj->reg_set = obj->mask;
     else
@@ -41,8 +42,7 @@ static inline void gpio_write(gpio_t *obj, int value) {
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    if (obj->pin == (PinName)NC)
-        return 0;
+    assert(obj->pin != (PinName)NC);
     return ((*obj->reg_in & obj->mask) ? 1 : 0);
 }
 
diff --git a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/pinmap.c b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/pinmap.c
index fce1147797..e7c7fe25f6 100644
--- a/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/pinmap.c
+++ b/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/pinmap.c
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <assert.h>
 #include "pinmap.h"
 #include "error.h"
 
@@ -20,7 +21,7 @@
  * Set the pin into input, output, alternate function or analog mode
  */
 void pin_function(PinName pin, int data) {
-    if (pin == (uint32_t)NC) return;
+    assert(pin != (PinName)NC);
     
     int mode = STM_PIN_MODE(data);
     int func = STM_PIN_FUNC(data);
@@ -53,7 +54,7 @@ void pin_function(PinName pin, int data) {
 }
 
 void pin_mode(PinName pin, PinMode mode) {
-    if (pin == (uint32_t)NC) { return; }
+    assert(pin != (PinName)NC);
 
     uint32_t pin_number = (uint32_t)pin;
     int port_index = pin_number >> 4;