libshell: update shell_ping()

make it faster.

programs/develop/ktcc/trunk/lib/libshell/shell_ping.c

@@ -1,12 +1,23 @@
 #include <shell_api.h>
 #include <sys/ksys.h>
 
+#define SHELL_PING_TIMEOUT 10 // 0.1 sec
+#define SHELL_PING_MIN_DELAY 1
+
 int shell_ping()
 {
     *__shell_shm = SHELL_PING;
 
-    _ksys_thread_yield();
-    _ksys_delay(40);
+    _ksys_thread_yield();   // hope shell is fast enough
 
-    return *__shell_shm == SHELL_OK;
+    size_t i = 0;
+    while (*__shell_shm != SHELL_OK){
+        if (i > (SHELL_PING_TIMEOUT / SHELL_PING_MIN_DELAY)) {
+            return 0;
+        }
+        i++;
+        _ksys_delay(SHELL_PING_MIN_DELAY);
+    }
+
+    return 1;
 }