diff --git a/examples/main.c b/examples/main.c
old mode 100644
new mode 100755
index 6d51773..e5a7c03
--- a/examples/main.c
+++ b/examples/main.c
@@ -3,28 +3,29 @@
 struct Timer timer1;
 struct Timer timer2;
 
-void timer1_callback()
+void timer1_callback(void *arg)
 {
-    printf("timer1 timeout!\r\n");
+    printf("timer1 timeout! arg: %p\r\n", arg);
 }
 
-void timer2_callback()
+void timer2_callback(void *arg)
 {
-    printf("timer2 timeout!\r\n");
+    printf("timer2 timeout! arg: %p\r\n", arg);
 }
 
-int main()
+int main(void)
 {
-	timer_init(&timer1, timer1_callback, 1000, 1000); //1s loop
+	timer_init(&timer1, timer1_callback, 1000, 1000, NULL); //1s loop
 	timer_start(&timer1);
 	
-	timer_init(&timer2, timer2_callback, 50, 0); //50ms delay
+	timer_init(&timer2, timer2_callback, 50, 0, NULL); //50ms delay
 	timer_start(&timer2);
 	
-	while(1) {
-	    
+	while(1) {	    
 	    timer_loop();
 	}
+
+    return 0;
 }
 
 void HAL_SYSTICK_Callback(void)
diff --git a/examples/test_linux.c b/examples/test_linux.c
old mode 100644
new mode 100755
index 85ff2ae..5acb1a2
--- a/examples/test_linux.c
+++ b/examples/test_linux.c
@@ -1,15 +1,52 @@
 #include <stdio.h>
 #include <signal.h>
 #include <sys/time.h>
+#include <time.h>
+#include <stdarg.h>
+#include <string.h>
+
 #include "../multi_timer.h"
 
+#define LOG_TIMESTAMP_FORMAT    "[%Y-%m-%d %H:%M:%S]"
+#define LOG_TIMESTAMP_LEN       21
+#define MS_TIMESTAMP_LEN        5
+
+int32_t printf_timestamp(const char *msg, ...)
+{
+    char content[1024] = {0};
+    time_t  time_write;
+    struct tm tm_Log;
+    struct timeval t; 
+    uint32_t len = 0;
+    va_list vl_list;
+
+    time_write = time(NULL);
+    localtime_r(&time_write, &tm_Log);
+    strftime((char *)&content[len], sizeof(content) - len - 1, LOG_TIMESTAMP_FORMAT, &tm_Log);
+    len = strlen(&content[len]);
+
+    /* .msec] */
+    gettimeofday(&t, NULL);
+    len--; // min a ']' char           
+    snprintf((char*)&content[len], sizeof(content) - len, ".%03d]", (int)(t.tv_usec / 1000));        
+    len += MS_TIMESTAMP_LEN; 
+
+    va_start(vl_list, msg);
+    vsnprintf((char *)&content[len], sizeof(content) - len - 1, (const char *)msg, vl_list);
+    va_end(vl_list);
+
+    printf("%s", content);
+
+    return 0;
+}
+
 void signalHandler(int signo)
 {
     switch(signo)
     {
         case SIGALRM:
             timer_ticks();
-            //printf("Caught the SIGALRM signal!\n");
+            //printf_timestamp("Caught the SIGALRM signal every 1ms !\n");
             break;
     }
 }
@@ -17,36 +54,38 @@ void signalHandler(int signo)
 struct Timer timer1;
 struct Timer timer2;
 
-void timer1_callback()
+void timer1_callback(void *arg)
 {
-    printf("timer1 timeout!\r\n");
+    printf_timestamp("timer1 timeout! arg: %p\r\n", arg);
 }
 
-void timer2_callback()
+void timer2_callback(void *arg)
 {
-    printf("timer2 timeout!\r\n");
+    printf_timestamp("timer2 timeout! arg: %p\r\n", arg);
 }
 
 int main(void)
 {
+    printf_timestamp("%s start ...\r\n", __func__);
+
     signal(SIGALRM, signalHandler);
 
     struct itimerval new_value, old_value;
-    new_value.it_value.tv_sec     = 1;
-    new_value.it_value.tv_usec    = 0;
+    new_value.it_value.tv_sec     = 0; // should be 0x00 !!!
+    new_value.it_value.tv_usec    = 1; // non-zero is OK !!!
     new_value.it_interval.tv_sec  = 0;
-    new_value.it_interval.tv_usec = 1000;
+    new_value.it_interval.tv_usec = 1000 * CFG_TIMER_1_TICK_N_MS; // 1ms
     setitimer(ITIMER_REAL, &new_value, &old_value);
 
-    timer_init(&timer1, timer1_callback, 4000, 1000);  // start timer after 4s
+    timer_init(&timer1, timer1_callback, 4000, 1000, &timer1);  // start timer after 4s
     timer_start(&timer1);
 
-    timer_init(&timer2, timer2_callback, 0, 2000);
+    timer_init(&timer2, timer2_callback, 0, 2000, &timer2); // start timer right now
     timer_start(&timer2);
 
-    while(1)
-    {
+    while(1) {
         timer_loop();
     }
+    
     return 0;
 }