From 36f97f19b44471f2ed1a3bd37e096ce32a852a1f Mon Sep 17 00:00:00 2001
From: Paul Sokolovsky <pfalcon@users.sourceforge.net>
Date: Fri, 14 Oct 2016 22:19:45 +0300
Subject: [PATCH] extmod/utime_mphal: sleep_us/ms(): Don't wait on negative
 argument.

---
 extmod/utime_mphal.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/extmod/utime_mphal.c b/extmod/utime_mphal.c
index 9471ad5252..3ecdc94469 100644
--- a/extmod/utime_mphal.c
+++ b/extmod/utime_mphal.c
@@ -46,13 +46,19 @@ STATIC mp_obj_t time_sleep(mp_obj_t seconds_o) {
 MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_obj, time_sleep);
 
 STATIC mp_obj_t time_sleep_ms(mp_obj_t arg) {
-    mp_hal_delay_ms(mp_obj_get_int(arg));
+    mp_int_t ms = mp_obj_get_int(arg);
+    if (ms > 0) {
+        mp_hal_delay_ms(ms);
+    }
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_ms_obj, time_sleep_ms);
 
 STATIC mp_obj_t time_sleep_us(mp_obj_t arg) {
-    mp_hal_delay_us(mp_obj_get_int(arg));
+    mp_int_t us = mp_obj_get_int(arg);
+    if (us > 0) {
+        mp_hal_delay_us(us);
+    }
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_us_obj, time_sleep_us);