diff --git a/lib/sleep.py b/lib/sleep.py
index d653872..c4208d2 100644
--- a/lib/sleep.py
+++ b/lib/sleep.py
@@ -4,16 +4,18 @@ ___license___ = "MIT"
 
 import time
 
-def sleep_ms(duration):
-    # todo: deepsleep?
-    time.sleep_ms(duration)
 
-def sleep(duration):
+def sleep_ms(duration):
     start_time = time.ticks_ms()
-    end_time = start_time + duration * 1000
+    end_time = start_time + duration
     while time.ticks_ms() < end_time:
         wfi()
 
+
+def sleep(duration):
+    sleep_ms(duration * 1000)
+    
+
 def wfi():
     # todo: this is fake
-    sleep_ms(1)
+    time.sleep_ms(1)
diff --git a/lib/test_sleep.py b/lib/test_sleep.py
index b653f92..bb6839f 100644
--- a/lib/test_sleep.py
+++ b/lib/test_sleep.py
@@ -14,5 +14,13 @@ class TestSleep(unittest.TestCase):
         sleep.sleep(sleep_secs)
         self.assertTrue(time.ticks_ms() >= time_after)
 
+    def test_sleep_ms(self):
+        sleep_ms = 3000
+        time_before = time.ticks_ms()
+        time_after = time_before + sleep_ms
+        sleep.sleep_ms(sleep_ms)
+        self.assertTrue(time.ticks_ms() >= time_after)
+
+
 if __name__ == '__main__':
     unittest.main()