Enable Heap for nRF51822

Fix the undefined symbol NRF_SRAM_END
Configure SRAM part for Heap

bsp/nrf51822/applications/startup.c

@@ -28,13 +28,13 @@ extern int  rt_application_init(void);
 
 #ifdef __CC_ARM
 extern int Image$$RW_IRAM1$$ZI$$Limit;
-#define NRF_SRAM_BEGIN    (&Image$$RW_IRAM1$$ZI$$Limit)
+#define NRF_HEAP_BEGIN    (&Image$$RW_IRAM1$$ZI$$Limit)
 #elif __ICCARM__
 #pragma section="HEAP"
-#define NRF_SRAM_BEGIN    (__segment_end("HEAP"))
+#define NRF_HEAP_BEGIN    (__segment_end("HEAP"))
 #else
 extern int __bss_end;
-#define NRF_SRAM_BEGIN    (&__bss_end)
+#define NRF_HEAP_BEGIN    (&__bss_end)
 #endif
 
 /**
@@ -58,7 +58,7 @@ void rtthread_startup(void)
     rt_system_timer_init();
 
 #ifdef RT_USING_HEAP
-    rt_system_heap_init((void*)NRF_SRAM_BEGIN, (void*)NRF_SRAM_END);
+    rt_system_heap_init((void*)NRF_HEAP_BEGIN, (void*)NRF_SRAM_END);
 #endif
 
     /* init scheduler system */

bsp/nrf51822/drivers/board.h

@@ -12,6 +12,12 @@
 #ifndef __BOARD_H__
 #define __BOARD_H__
 
+// <o> Internal SRAM memory size[Kbytes] <16 or 32>
+//  <i>Default: 16
+#define NRF_SRAM_BEGIN	(0x20000000)
+#define NRF_SRAM_SIZE	(16 * 1024)
+#define NRF_SRAM_END	(NRF_SRAM_BEGIN + NRF_SRAM_SIZE)
+//#endif
 
 
 void rt_hw_board_init(void);

bsp/nrf51822/rtconfig.h

@@ -49,10 +49,10 @@
 
 /* SECTION: Memory Management */
 /* Using Memory Pool Management*/
-/* #define RT_USING_MEMPOOL */
+#define RT_USING_MEMPOOL
 
 /* Using Dynamic Heap Management */
-//#define RT_USING_HEAP
+#define RT_USING_HEAP
 
 /* Using Small MM */
 #define RT_USING_SMALL_MEM