diff --git a/interface_handler.py b/interface_handler.py
index d521cc2..f305629 100644
--- a/interface_handler.py
+++ b/interface_handler.py
@@ -72,7 +72,8 @@ class Interface_handler:
                     GPIO.setup(self.Pin[pin].value,GPIO.OUT)
                 elif protocol =="PWM":
                     GPIO.setup(self.Pin[pin].value,GPIO.OUT)
-                    self.pwms[self.Pin[pin].value] = GPIO.PWM(self.Pin[pin].value,frequency)
+                    pwm = GPIO.PWM(self.Pin[pin].value,frequency)
+                    self.pwms[self.Pin[pin].value] = pwm
                 else:
                     raise NotImplementedError('the protocol of the device %s is not implemented' % device_name)
                 
@@ -102,11 +103,11 @@ class Interface_handler:
         for pin in self.xml_reader.get_port(device_name)["pins"]:
             if protocol in ["DO","DI"]:
                 returnValues.update({
-                    pin : GPIO.input(self.Pin[pin].value)
+                    pin : str(GPIO.input(self.Pin[pin].value))
                 })
-            if protocol in ["PWM"]:
+            elif protocol in ["PWM"]:
                 returnValues.update({
-                    pin : self.pwm_dutycycles[self.Pin[pin].value]
+                    pin : str(self.pwm_dutycycles[self.Pin[pin].value])
                 })
             else: #throw error for protocols without write functionality
                 raise ValueError("you can not read from device %s" % device_name)
@@ -157,7 +158,7 @@ class Interface_handler:
                     raise ValueError(str("pin %s is not a part of device %s",pin,device_name))
                 dutycycle = int(output[pin])
                 self.pwm_dutycycles[self.Pin[pin].value] = dutycycle
-                if not dutycycle in range(1,100,1):
+                if not dutycycle in range(0,100,1):
                     raise TypeError("value must be a whole number between 0 and 100")
                 self.pwms[self.Pin[pin].value].stop()
                 self.pwms[self.Pin[pin].value].start(dutycycle)