diff --git a/HISTORY.rst b/HISTORY.rst
index f5ace81f..39d82662 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -15,9 +15,10 @@ PlatformIO 3.0
   `library.json <http://docs.platformio.org/page/librarymanager/config.html>`__
   and ``srcFilter`` field
 * Do not ask for board ID when initialize project for desktop platform
-* Fixed issue when can not load broken PIO Core state
+* Handle broken PIO Core state and create new one
 * Fixed an issue with a custom transport for `PIO Unit Testing <http://docs.platformio.org/page/plus/unit-testing.html>`__
   when multiple tests are present
+* Fixed an issue when can not upload firmware to SAM-BA based board (Due)
 
 3.4.0 (2017-06-26)
 ~~~~~~~~~~~~~~~~~~
diff --git a/platformio/builder/tools/pioupload.py b/platformio/builder/tools/pioupload.py
index a45409e6..0ff3cb1f 100644
--- a/platformio/builder/tools/pioupload.py
+++ b/platformio/builder/tools/pioupload.py
@@ -48,7 +48,7 @@ def TouchSerialPort(env, port, baudrate):
         s.close()
     except:  # pylint: disable=W0702
         pass
-    sleep(0.4)
+    sleep(0.4)  # DO NOT REMOVE THAT (required by SAM-BA based boards)
 
 
 def WaitForNewSerialPort(env, before):