[BEETLE] Add LED Emulation

The current version of MBED test environment requires LEDs to be present
in the platform.

Beetle HW does not provide any user programmable LEDs. This patch provides an
emulation of the feature by using dummy PINs.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

hal/targets/hal/TARGET_ARM_SSG/TARGET_BEETLE/PinNames.h

@@ -126,13 +126,14 @@ typedef enum {
     SENSOR_SDA = 506,
     SENSOR_SCL = 507,
 
+    // Emulated LEDS
+    LED1 = 1001,
+    LED2 = 1002,
+    LED3 = 1003,
+    LED4 = 1004,
+
     // Not connected
     NC = (int)0xFFFFFFFF,
-    // LEDS not connected
-    LED1 = NC,
-    LED2 = NC,
-    LED3 = NC,
-    LED4 = NC,
 } PinName;
 
 typedef enum {

hal/targets/hal/TARGET_ARM_SSG/TARGET_BEETLE/gpio_api.c

@@ -24,6 +24,9 @@ uint32_t gpio_set(PinName pin) {
         pin_value = pin;
     } else if (pin >= 16 && pin <= 31) {
         pin_value = pin-16;
+    } else if (pin >= 1001 && pin <= 1004) {
+        /* Emulated LEDs */
+        return (1);
     }
 
     pin_function(pin, 0);
@@ -44,6 +47,9 @@ void gpio_init(gpio_t *obj, PinName pin) {
             pin_value = pin;
         } else if (pin >= 16 && pin <= 31) {
             pin_value = pin-16;
+        } else if (pin >= 1001 && pin <= 1004) {
+            /* Emulated LEDs */
+            return;
         }
 
         obj->mask = 0x1 << pin_value;

hal/targets/hal/TARGET_ARM_SSG/TARGET_BEETLE/gpio_object.h

@@ -37,15 +37,25 @@ typedef struct {
 } gpio_t;
 
 static inline void gpio_write(gpio_t *obj, int value) {
-    if (value == 1){
-        *obj->reg_data |= (obj->mask);
-    } else if (value == 0){
-        *obj->reg_data &= ~(obj->mask);
+    if (obj->pin < LED1 || obj->pin > LED4) {
+        if (value == 1) {
+            *obj->reg_data |= (obj->mask);
+        } else if (value == 0){
+            *obj->reg_data &= ~(obj->mask);
+        }
+    } else {
+        /* Emulated LEDs return without taking any action */
+        return;
     }
 }
 
 static inline int gpio_read(gpio_t *obj) {
-    return ((*obj->reg_in & obj->mask) ? 1 : 0);
+    if (obj->pin < LED1 || obj->pin > LED4) {
+        return ((*obj->reg_in & obj->mask) ? 1 : 0);
+    } else {
+        /* Emulated LEDs return OFF always */
+        return 0;
+    }
 }
 
 #ifdef __cplusplus