[XDOT_L151] add RTOS configuration for xDot

Author: mfiore02

hal/targets/cmsis/TARGET_STM/mbed_rtx.h

@@ -647,6 +647,21 @@
 #define OS_CLOCK                32000000
 #endif
 
+#elif defined(TARGET_XDOT_L151CC)
+
+#ifndef INITIAL_SP
+#define INITIAL_SP              (0x20008000UL)
+#endif
+#ifndef OS_TASKCNT
+#define OS_TASKCNT              6
+#endif
+#ifndef OS_MAINSTKSIZE
+#define OS_MAINSTKSIZE          128
+#endif
+#ifndef OS_CLOCK
+#define OS_CLOCK                32000000
+#endif
+
 #elif defined(TARGET_STM32L476VG)
 
 #ifndef INITIAL_SP