diff --git a/components/libc/compilers/armlibc/sys/types.h b/components/libc/compilers/armlibc/sys/types.h
index 2aad77c99d..78fee1bb99 100644
--- a/components/libc/compilers/armlibc/sys/types.h
+++ b/components/libc/compilers/armlibc/sys/types.h
@@ -5,20 +5,22 @@
  *
  * Change Logs:
  * Date           Author       Notes
- * 2020-09-05 Meco Man  fix bugs
+ * 2020-09-05     Meco Man     fix bugs
+ * 2020-12-16     Meco Man     add useconds_t
  */
 #ifndef __TYPES_H__
 #define __TYPES_H__
 
 #include <stdint.h>
 
-typedef int32_t clockid_t;
-typedef int32_t key_t;       /* Used for interprocess communication. */
-typedef int32_t pid_t;       /* Used for process IDs and process group IDs. */
+typedef int32_t          clockid_t;
+typedef int32_t          key_t;         /* Used for interprocess communication. */
+typedef int32_t          pid_t;         /* Used for process IDs and process group IDs. */
 #ifndef ARCH_CPU_64BIT
-typedef signed int   ssize_t;  /* Used for a count of bytes or an error indication. */
+typedef signed int       ssize_t;       /* Used for a count of bytes or an error indication. */
 #else
-typedef long signed int   ssize_t;  /* Used for a count of bytes or an error indication. */
+typedef long signed int  ssize_t;       /* Used for a count of bytes or an error indication. */
 #endif
+typedef unsigned long    useconds_t;    /* microseconds (unsigned) */
 
 #endif
diff --git a/components/libc/compilers/armlibc/sys/unistd.h b/components/libc/compilers/armlibc/sys/unistd.h
index 549771e8f4..73a73a267e 100644
--- a/components/libc/compilers/armlibc/sys/unistd.h
+++ b/components/libc/compilers/armlibc/sys/unistd.h
@@ -5,11 +5,13 @@
  *
  * Change Logs:
  * Date           Author       Notes
+ * 2020-12-16     Meco Man     add usleep
  */
 #ifndef _SYS_UNISTD_H
 #define _SYS_UNISTD_H
 
-#include <rtthread.h>
+#include <rtconfig.h>
+#include "types.h"
 
 #ifdef RT_USING_DFS
 
@@ -69,5 +71,6 @@ int     isatty      (int fd);
 char *  ttyname     (int desc);
 
 unsigned int sleep(unsigned int seconds);
+int usleep(useconds_t usec);
 
 #endif /* _SYS_UNISTD_H */
diff --git a/components/libc/compilers/common/sys/time.h b/components/libc/compilers/common/sys/time.h
index 952dbf32a5..28a977c1f9 100644
--- a/components/libc/compilers/common/sys/time.h
+++ b/components/libc/compilers/common/sys/time.h
@@ -36,8 +36,7 @@ struct timeval {
 };
 #endif /* _TIMEVAL_DEFINED */
 
-#ifndef _TIMESPEC
-#define _TIMESPEC
+#if !defined __GNUC__ && !defined __ICCARM__
 struct timespec {
     time_t  tv_sec;     /* seconds */
     long    tv_nsec;    /* and nanoseconds */
diff --git a/components/libc/compilers/dlib/sys/types.h b/components/libc/compilers/dlib/sys/types.h
index 001ace4dd2..7dbeddcaa9 100644
--- a/components/libc/compilers/dlib/sys/types.h
+++ b/components/libc/compilers/dlib/sys/types.h
@@ -5,20 +5,21 @@
  *
  * Change Logs:
  * Date           Author       Notes
+ * 2020-12-16     Meco Man     add useconds_t
  */
 #ifndef __TYPES_H__
 #define __TYPES_H__
 
 #include <stdint.h>
-#include <rtthread.h>
 
-typedef rt_int32_t clockid_t;
-typedef rt_int32_t key_t;       /* Used for interprocess communication. */
-typedef rt_int32_t pid_t;       /* Used for process IDs and process group IDs. */
+typedef int32_t          clockid_t;
+typedef int32_t          key_t;         /* Used for interprocess communication. */
+typedef int32_t          pid_t;         /* Used for process IDs and process group IDs. */
 #ifndef ARCH_CPU_64BIT
-typedef signed int   ssize_t;  /* Used for a count of bytes or an error indication. */
+typedef signed int       ssize_t;       /* Used for a count of bytes or an error indication. */
 #else
-typedef long signed int   ssize_t;  /* Used for a count of bytes or an error indication. */
+typedef long signed int  ssize_t;       /* Used for a count of bytes or an error indication. */
 #endif
+typedef unsigned long    useconds_t;    /* microseconds (unsigned) */
 
 #endif
diff --git a/components/libc/compilers/dlib/sys/unistd.h b/components/libc/compilers/dlib/sys/unistd.h
index 982a29135d..6d99cd6c55 100644
--- a/components/libc/compilers/dlib/sys/unistd.h
+++ b/components/libc/compilers/dlib/sys/unistd.h
@@ -5,10 +5,14 @@
  *
  * Change Logs:
  * Date           Author       Notes
+ * 2020-12-16     Meco Man     add usleep
  */
 #ifndef _SYS_UNISTD_H
 #define _SYS_UNISTD_H
 
+#include <rtconfig.h>
+#include "types.h"
+
 #ifdef RT_USING_DFS
 
 #define STDIN_FILENO    0       /* standard input file descriptor */
@@ -41,5 +45,6 @@ int     isatty      (int fd);
 char *  ttyname     (int desc);
 
 unsigned int sleep(unsigned int seconds);
+int usleep(useconds_t usec);
 
 #endif /* _SYS_UNISTD_H */
diff --git a/components/libc/time/posix_sleep.c b/components/libc/time/posix_sleep.c
index f21b0a7994..e50bda7d4a 100644
--- a/components/libc/time/posix_sleep.c
+++ b/components/libc/time/posix_sleep.c
@@ -5,10 +5,10 @@
  *
  * Change Logs:
  * Date           Author       Notes
+ * 2020-12-16     Meco Man     add usleep
  */
-#include <stdlib.h>
 #include <rtthread.h>
-
+#include <rthw.h>
 #include <unistd.h>
 
 unsigned int sleep(unsigned int seconds)
@@ -21,3 +21,10 @@ unsigned int sleep(unsigned int seconds)
 
     return seconds - delta_tick/RT_TICK_PER_SECOND;
 }
+
+int usleep(useconds_t usec)
+{
+    rt_thread_mdelay(usec / 1000u);
+    rt_hw_us_delay(usec % 1000u);
+    return 0;
+}