diff --git a/components/esp8266/include/esp8266/rom_functions.h b/components/esp8266/include/esp8266/rom_functions.h
index c1f20370..6aeacb2b 100644
--- a/components/esp8266/include/esp8266/rom_functions.h
+++ b/components/esp8266/include/esp8266/rom_functions.h
@@ -17,7 +17,6 @@ uint32_t Wait_SPI_Idle();
 
 void uart_div_modify(uint32_t uart_no, uint32_t baud_div);
 
-void ets_delay_us(uint32_t us);
 int ets_io_vprintf(int (*putc)(int), const char* fmt, va_list ap);
 
 void system_soft_wdt_feed();
diff --git a/components/esp8266/include/rom/ets_sys.h b/components/esp8266/include/rom/ets_sys.h
index 4d176d92..b5cbf0a5 100644
--- a/components/esp8266/include/rom/ets_sys.h
+++ b/components/esp8266/include/rom/ets_sys.h
@@ -97,6 +97,16 @@ extern uint32_t WDEV_INTEREST_EVENT;
   */
 void os_delay_us(uint16_t us);
 
+/**
+  * @brief  CPU do while loop for some time.
+  *         In FreeRTOS task, please call FreeRTOS apis.
+  *
+  * @param  uint32_t us : Delay time in us.
+  *
+  * @return None
+  */
+void ets_delay_us(uint32_t us);
+
 /**
   * @brief     Register the print output function.
   *
diff --git a/components/newlib/newlib/port/time.c b/components/newlib/newlib/port/time.c
index fc65f33c..59684d09 100644
--- a/components/newlib/newlib/port/time.c
+++ b/components/newlib/newlib/port/time.c
@@ -19,6 +19,7 @@
 
 #include "esp_system.h"
 #include "esp_timer.h"
+#include "rom/ets_sys.h"
 
 #include "FreeRTOS.h"
 #include "task.h"
@@ -141,3 +142,26 @@ clock_t _times_r(struct _reent *r, struct tms *tms)
 
     return 0;
 }
+
+int usleep(useconds_t us)
+{
+    const int us_per_tick = portTICK_PERIOD_MS * 1000;
+
+    if (us < us_per_tick) {
+        ets_delay_us((uint32_t) us);
+    } else {
+        /* since vTaskDelay(1) blocks for anywhere between 0 and portTICK_PERIOD_MS,
+         * round up to compensate.
+         */
+        vTaskDelay((us + us_per_tick - 1) / us_per_tick);
+    }
+
+    return 0;
+}
+
+unsigned int sleep(unsigned int seconds)
+{
+    vTaskDelay(seconds * (1000 / portTICK_PERIOD_MS));
+
+    return 0;
+}