diff --git a/Sming/Makefile b/Sming/Makefile
index 7ae4885dd2..9d34e46a49 100644
--- a/Sming/Makefile
+++ b/Sming/Makefile
@@ -181,6 +181,7 @@ EXTRA_INCDIR     += third-party/ws_parser/
 # => SDK
 ifneq (,$(findstring third-party/ESP8266_NONOS_SDK, $(SDK_BASE)))
 	THIRD_PARTY_DATA += third-party/ESP8266_NONOS_SDK/Makefile
+	CFLAGS += -DSDK_INTERNAL
 endif
 
 # => esp-gdbstub
@@ -233,7 +234,7 @@ endif
 MFORCE32 := $(shell $(CC) --help=target | grep mforce-l32)
 
 # compiler flags using during compilation of source files. Add '-pg' for debugging
-CFLAGS = -Wpointer-arith -Wundef -Werror -Wl,-EL -nostdlib -mlongcalls -mtext-section-literals -finline-functions -fdata-sections -ffunction-sections \
+CFLAGS += -Wpointer-arith -Wundef -Werror -Wl,-EL -nostdlib -mlongcalls -mtext-section-literals -finline-functions -fdata-sections -ffunction-sections \
          -D__ets__ -DICACHE_FLASH -DARDUINO=106 -DCOM_SPEED_SERIAL=$(COM_SPEED_SERIAL) -DENABLE_CMD_EXECUTOR=$(ENABLE_CMD_EXECUTOR) -DESP8266=1
 ifeq ($(SMING_RELEASE),1)
 	# See: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
diff --git a/Sming/Makefile-project.mk b/Sming/Makefile-project.mk
index 52090080b9..1d373ed6c7 100644
--- a/Sming/Makefile-project.mk
+++ b/Sming/Makefile-project.mk
@@ -217,6 +217,10 @@ endif
 
 # compiler flags using during compilation of source files
 CFLAGS		= -Wpointer-arith -Wundef -Werror -Wl,-EL -nostdlib -mlongcalls -mtext-section-literals -finline-functions -fdata-sections -ffunction-sections -D__ets__ -DICACHE_FLASH -DARDUINO=106 -DCOM_SPEED_SERIAL=$(COM_SPEED_SERIAL) $(USER_CFLAGS) -DENABLE_CMD_EXECUTOR=$(ENABLE_CMD_EXECUTOR)
+# => SDK
+ifneq (,$(findstring third-party/ESP8266_NONOS_SDK, $(SDK_BASE)))
+	CFLAGS += -DSDK_INTERNAL
+endif
 ifeq ($(SMING_RELEASE),1)
 	# See: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
 	#      for full list of optimization options
diff --git a/Sming/Makefile-rboot.mk b/Sming/Makefile-rboot.mk
index 32ab0599c3..912bb2cd9d 100644
--- a/Sming/Makefile-rboot.mk
+++ b/Sming/Makefile-rboot.mk
@@ -195,6 +195,10 @@ USER_LIBDIR  = $(SMING_HOME)/compiler/lib/
 
 # compiler flags using during compilation of source files
 CFLAGS		= -Wpointer-arith -Wundef -Werror -Wl,-EL -nostdlib -mlongcalls -mtext-section-literals -finline-functions -fdata-sections -ffunction-sections -D__ets__ -DICACHE_FLASH -DARDUINO=106 -DCOM_SPEED_SERIAL=$(COM_SPEED_SERIAL) $(USER_CFLAGS) -DENABLE_CMD_EXECUTOR=$(ENABLE_CMD_EXECUTOR)
+# => SDK
+ifneq (,$(findstring third-party/ESP8266_NONOS_SDK, $(SDK_BASE)))
+	CFLAGS += -DSDK_INTERNAL
+endif
 ifeq ($(SMING_RELEASE),1)
 	# See: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
 	#      for full list of optimization options
diff --git a/Sming/system/include/esp_systemapi.h b/Sming/system/include/esp_systemapi.h
index 4c7a492160..4c964a2a54 100644
--- a/Sming/system/include/esp_systemapi.h
+++ b/Sming/system/include/esp_systemapi.h
@@ -3,7 +3,7 @@
 #ifndef __ESP_SYSTEM_API_H__
 #define __ESP_SYSTEM_API_H__
 
-#include "ets_sys.h"
+#include <ets_sys.h>
 #include <osapi.h>
 #include <gpio.h>
 #include <os_type.h>
@@ -43,6 +43,63 @@
 #endif
 #define assert(condition) if (!(condition)) SYSTEM_ERROR("ASSERT: %s %d", __FUNCTION__, __LINE__)
 #define SYSTEM_ERROR(fmt, ...) m_printf("ERROR: " fmt "\r\n", ##__VA_ARGS__)
+
+#ifndef SDK_INTERNAL
+extern void ets_timer_arm_new(ETSTimer *ptimer, uint32_t milliseconds, bool repeat_flag, int isMstimer);
+extern void ets_timer_disarm(ETSTimer *a);
+extern void ets_timer_setfn(ETSTimer *t, ETSTimerFunc *pfunction, void *parg);
+
+//extern void ets_wdt_init(uint32_t val); // signature?
+extern void ets_wdt_enable(void);
+extern void ets_wdt_disable(void);
+extern void wdt_feed(void);
+//extern void wd_reset_cnt(void);
+extern void ets_delay_us(uint32_t us);
+
+extern void ets_isr_mask(unsigned intr);
+extern void ets_isr_unmask(unsigned intr);
+
+typedef void (* ets_isr_t)(void *);
+
+//extern void ets_isr_attach(int intr, void *handler, void *arg);
+extern void ets_isr_attach(int i, ets_isr_t func, void *arg);
+
+extern int ets_memcmp(const void *s1, const void *s2, size_t n);
+extern void *ets_memcpy(void *dest, const void *src, size_t n);
+extern void *ets_memset(void *s, int c, size_t n);
+
+//extern void ets_install_putc1(void *routine);
+extern void ets_install_putc1(void (*p)(char c));
+extern int ets_sprintf(char *str, const char *format, ...)  __attribute__ ((format (printf, 2, 3)));
+extern int ets_str2macaddr(void *, void *);
+extern int ets_strcmp(const char *s1, const char *s2);
+extern char *ets_strcpy(char *dest, const char *src);
+//extern int os_random();
+//extern char *ets_strdup(const char *str); // :(
+const char * ets_strrchr(const char *str, int character);
+extern int ets_strlen(const char *s);
+extern int ets_strncmp(const char *s1, const char *s2, unsigned int len);
+extern char *ets_strncpy(char *dest, const char *src, size_t n);
+extern char *ets_strstr(const char *haystack, const char *needle);
+extern int os_printf_plus(const char *format, ...)  __attribute__ ((format (printf, 1, 2)));
+extern int os_snprintf(char *str, size_t size, const char *format, ...) __attribute__ ((format (printf, 3, 4)));
+extern int ets_vsnprintf(char * s, size_t n, const char * format, va_list arg) __attribute__ ((format (printf, 3, 0)));
+
+extern void *pvPortMalloc(size_t xWantedSize, const char *file, uint32 line);
+extern void *pvPortZalloc(size_t xWantedSize, const char *file, uint32 line);
+extern void pvPortFree(void *ptr);
+extern void vPortFree(void *ptr, const char *file, uint32 line);
+extern void *vPortMalloc(size_t xWantedSize);
+
+extern void uart_div_modify(uint8 uart_no, uint32 DivLatchValue);
+extern int ets_uart_printf(const char *fmt, ...);
+extern void uart_tx_one_char(char ch);
+
+extern void ets_intr_lock();
+extern void ets_intr_unlock();
+
+#endif /* SDK_INTERNAL */
+
 // CPU Frequency
 extern void ets_update_cpu_frequency(uint32_t frq);
 extern uint32_t ets_get_cpu_frequency();