1 files changed, 6 insertions, 1 deletions
diff --git a/esp8266/modules/ds18x20.py b/esp8266/modules/ds18x20.py
index eb22e2ae30..bf06094835 100644
--- a/esp8266/modules/ds18x20.py
+++ b/esp8266/modules/ds18x20.py
@@ -1,6 +1,8 @@
 # DS18x20 temperature sensor driver for MicroPython.
 # MIT license; Copyright (c) 2016 Damien P. George
 
+from micropython import const
+
 _CONVERT = const(0x44)
 _RD_SCRATCH = const(0xbe)
 _WR_SCRATCH = const(0x4e)
@@ -43,4 +45,7 @@ class DS18X20:
                 t = buf[0] >> 1
             return t - 0.25 + (buf[7] - buf[6]) / buf[7]
         else:
-            return (buf[1] << 8 | buf[0]) / 16
+            t = buf[1] << 8 | buf[0]
+            if t & 0x8000: # sign bit set
+                t = -((t ^ 0xffff) + 1)
+            return t / 16