* updated port apis with corrections.

libraries/mbed/targets/hal/TARGET_Atmel/TARGET_SAM0/port_api.c

@@ -22,21 +22,12 @@
 #define PORTB_MASK	0xC0C3C30D  // mask for available pins in Port B
 #define PORTC_MASK	0x000D0000  // mask for available pins in Port C
 
-#define PORTA_START	0  // 32 pins in a port
-#define PORTB_START	32
-#define PORTC_START	64
-
 uint32_t start_pin(PortName port)
 {
-    switch (port) {
+    if(port <= 2) { /* PortC value is 2*/
-        case PortA:
+        return port * 32;
-            return PORTA_START;
+    } else {
-        case PortB:
+        return NC;
-            return PORTB_START;
-        case PortC:
-            return PORTC_START;
-        default:
-            return NC;
     }
 }
 void port_init(port_t *obj, PortName port, int mask, PinDirection dir)
@@ -46,26 +37,7 @@ void port_init(port_t *obj, PortName port, int mask, PinDirection dir)
     int i, j;
     int start;
 
-    PortGroup *const port_base = (PortGroup*)port_get_group_from_gpio_pin(port * 32);  // 32 pins in port // function reused to get the port base
-    switch (port) {
-        case PortA:
-            obj->mask = (uint32_t)mask & PORTA_MASK;
-            break;
-        case PortB:
-            obj->mask = (uint32_t)mask & PORTB_MASK;
-            break;
-        case PortC:
-            obj->mask = (uint32_t)mask & PORTC_MASK;
-            break;
-    }
-    start = start_pin(port);
-    if(start == NC)
-        return;
-    obj->port = port;
-    obj->direction = dir;
     port_get_config_defaults(&pin_conf);
-    obj->powersave = pin_conf.powersave;
-    obj->mode = PORT_PIN_PULL_UP;
     switch (dir) {
         case PIN_INPUT :
             pin_conf.direction  = PORT_PIN_DIR_INPUT;
@@ -76,8 +48,34 @@ void port_init(port_t *obj, PortName port, int mask, PinDirection dir)
         case PIN_INPUT_OUTPUT:
             pin_conf.direction  = PORT_PIN_DIR_OUTPUT_WTH_READBACK;
             break;
+        default:
+            return;
     }
-    for (i = start, j = 0; i < (start + 32); i++, j++) {
+
+    PortGroup *const port_base = (PortGroup*)port_get_group_from_gpio_pin(port * 32);  // 32 pins in port // function reused to get the port base
+    if(port_base == NULL) return; /* returns NULL if invalid*/
+    switch (port) {
+        case PortA:
+            obj->mask = (uint32_t)mask & PORTA_MASK;
+            break;
+        case PortB:
+            obj->mask = (uint32_t)mask & PORTB_MASK;
+            break;
+        case PortC:
+            obj->mask = (uint32_t)mask & PORTC_MASK;
+            break;
+        default:
+            return;
+    }
+    start = start_pin(port);
+    if(start == NC)
+        return;
+    obj->port = port;
+    obj->direction = dir;
+    obj->powersave = pin_conf.powersave;
+    obj->mode = PORT_PIN_PULL_UP;
+
+    for (i = start, j = 0; j < 32; i++, j++) {
         if (obj->mask & (1<<j)) {
             port_pin_set_config((PinName)i, &pin_conf);
         }
@@ -96,7 +94,7 @@ void port_mode(port_t *obj, PinMode mode)
     start = start_pin(obj->port);
     if(start == NC)
         return;
-    for (i = start, j = 0; i < (start + 32); i++, j++) {
+    for (i = start, j = 0; j < 32; i++, j++) {
         if (obj->mask & (1<<j)) {
             pin_mode((PinName)i , mode);
         }
@@ -109,12 +107,7 @@ void port_dir(port_t *obj, PinDirection dir)
     struct port_config pin_conf;
     int i, j;
     int start;
-    start = start_pin(obj->port);
+
-    if(start == NC)
-        return;
-    obj->direction = dir;
-    pin_conf.input_pull = obj->mode;
-    pin_conf.powersave  = obj->powersave;
     switch (dir) {
         case PIN_INPUT :
             pin_conf.direction  = PORT_PIN_DIR_INPUT;
@@ -125,8 +118,17 @@ void port_dir(port_t *obj, PinDirection dir)
         case PIN_INPUT_OUTPUT:
             pin_conf.direction  = PORT_PIN_DIR_OUTPUT_WTH_READBACK;
             break;
+        default:
+            return;
     }
-    for (i = start, j = 0; i < (start + 32); i++, j++) {
+    start = start_pin(obj->port);
+    if(start == NC)
+        return;
+    obj->direction = dir;
+    pin_conf.input_pull = obj->mode;
+    pin_conf.powersave  = obj->powersave;
+
+    for (i = start, j = 0; j < 32; i++, j++) {
         if (obj->mask & (1<<j)) {
             port_pin_set_config((PinName)i, &pin_conf);
         }
@@ -155,9 +157,9 @@ void port_write(port_t *obj, int value)
 int port_read(port_t *obj)
 {
     MBED_ASSERT(obj);
-    if (obj->direction  == PIN_INPUT) {
+    if (obj->direction == PIN_OUTPUT) {
-        return (*obj->IN & obj->mask);
-    } else {
         return (*obj->OUT & obj->mask);
+    } else {
+        return (*obj->IN & obj->mask);
     }
 }