diff --git a/software/device.py b/software/device.py
index 1ab1cf5..27d4cd3 100644
--- a/software/device.py
+++ b/software/device.py
@@ -35,7 +35,8 @@ class Device:
         if self.fake:
             print 'pwm', which, duty
         else:
-            duty = 65535 - duty
+            if duty != 0:
+                duty = 65536 - duty
             self.epo.write('p' + chr(which) + chr(duty & 0xff) + chr(duty >> 8))
 
     # sets ddswave (wave=square,sine,saw1,saw2)
diff --git a/software/modules/ModuleDebug.py b/software/modules/ModuleDebug.py
index 2942156..32bf474 100644
--- a/software/modules/ModuleDebug.py
+++ b/software/modules/ModuleDebug.py
@@ -29,7 +29,7 @@ class ModuleDebugWidget(QWidget):
         # real device:
         self.dev = Device()
         # fake device:
-        # self.dev = Device(True)
+#        self.dev = Device(True)
 
         self.timer = QTimer()
         QObject.connect(self.timer, SIGNAL("timeout()"), self.read_inputs)