diff --git a/interface_handler.py b/interface_handler.py
index 611d159..743b987 100644
--- a/interface_handler.py
+++ b/interface_handler.py
@@ -1,7 +1,10 @@
 from enum import Enum
-from xml_reader import Xml_reader
 import RPi.GPIO as GPIO
+import sys
 
+sys.path.append('/home/pi/aped_device')
+
+from xml_reader import Xml_reader
 class Interface_handler:
     """handles the access to the various interfaces (e.g. GPIO)
     """
@@ -11,38 +14,41 @@ class Interface_handler:
 
         enables restricting methods to these pins
         """
-        GIO_2 = 3
-        GIO_3 = 5
-        GIO_4 = 7
-        GIO_5 = 29
-        GIO_6 = 31
-        GIO_7 = 26
-        GIO_8 = 24
-        GIO_9 = 21
-        GIO_10 = 19
-        GIO_11 = 23
-        GIO_12 = 32
-        GIO_13 = 33
-        GIO_14 = 8
-        GIO_15 = 10
-        GIO_16 = 36
-        GIO_17 = 11
-        GIO_18 = 12
-        GIO_19 = 35
-        GIO_20 = 38
-        GIO_21 = 40
-        GIO_22 = 15
-        GIO_23 = 16
-        GIO_24 = 18
-        GIO_25 = 22
-        GIO_26 = 37
-        GIO_27 = 13
+        GPIO_2 = 3
+        GPIO_3 = 5
+        GPIO_4 = 7
+        GPIO_5 = 29
+        GPIO_6 = 31
+        GPIO_7 = 26
+        GPIO_8 = 24
+        GPIO_9 = 21
+        GPIO_10 = 19
+        GPIO_11 = 23
+        GPIO_12 = 32
+        GPIO_13 = 33
+        GPIO_14 = 8
+        GPIO_15 = 10
+        GPIO_16 = 36
+        GPIO_17 = 11
+        GPIO_18 = 12
+        GPIO_19 = 35
+        GPIO_20 = 38
+        GPIO_21 = 40
+        GPIO_22 = 15
+        GPIO_23 = 16
+        GPIO_24 = 18
+        GPIO_25 = 22
+        GPIO_26 = 37
+        GPIO_27 = 13
 
-    def __init__(self, xml_reader):
+    def __init__(self, xml_reader: Xml_reader):
         """inits the interface_handler
         """
+        #type check xml_reader
         if not isinstance(xml_reader, Xml_reader):
             raise TypeError('xml_reader must be an instance of XML_reader')
+        
+        #initialise interface_handler
         self.xml_reader = xml_reader
         self.init_gpio()
 
@@ -51,17 +57,21 @@ class Interface_handler:
         """
         GPIO.setmode(GPIO.BOARD)
         for device_name in self.xml_reader.get_device_names():
-            protocol, pins in self.xml_reader.get_port(device_name)
+            port_info = self.xml_reader.get_port(device_name)
+            protocol = port_info["protocol"]
+            pins = port_info["pins"]
+
+            #setup pins
             for pin in pins:
-                if protocol == "AI" or "DI":
-                    GPIO.setup(self.Pin(pin),GPIO.IN)
-                elif protocol == "AO" or "DO":
-                    GPIO.setup(self.Pin(pin),GPIO.OUT)
+                if protocol == "DI":
+                    GPIO.setup(self.Pin[pin].value,GPIO.IN)
+                elif protocol == "DO":
+                    GPIO.setup(self.Pin[pin].value,GPIO.OUT)
                 else:
                     raise NotImplementedError('the protocol of the device %s is not implemented' % device_name)
                 
 
-    def read(self, device_name):
+    def read(self, device_name:str) -> dict:
         """reads the current value from the pins of one device
 
         Args:
@@ -73,20 +83,27 @@ class Interface_handler:
         Returns:
             dict:  {'pin': 'value'}
         """
+        #check device_name is valid
         if self.xml_reader.get_port(device_name) == None:
             raise NameError('the device with the name %s is unknown' % device_name)
+
         returnValues = dict()
-        protocol, pins = self.xml_reader.get_port(device_name)
-        if not protocol == "AI" or "DI":
-            raise ValueError("you can not read from device %s" % device_name)
+
+        port_info = self.xml_reader.get_port(device_name)
+        protocol = port_info["protocol"]
+        pins = port_info["pins"]
+
         for pin in self.xml_reader.get_port(device_name)["pins"]:
-            returnValues.update({
-                pin,
-                GPIO.read(self.Pin(pin))
-            })
+            if protocol == "DI":
+                returnValues.update({
+                    pin:GPIO.input(self.Pin[pin].value)
+                })
+            else: #throw error for protocols without write functionality
+                raise ValueError("you can not read from device %s" % device_name)
+
         return returnValues
 
-    def write(self, device_name, value):
+    def write(self, device_name:str, value):
         """writes a value to all the pins of a device
 
         Args:
@@ -96,13 +113,31 @@ class Interface_handler:
         Raises:
             NameError: device not found in config.xml
             TypeError: value has wrong type
+
+        Returns:
+            value if everything went well, None otherwise
         """
+        #check device_name is valid
         if self.xml_reader.get_port(device_name) == None:
             raise NameError('the device with the name %s is unknown' % device_name)
-        if not isinstance(value,float):
-            raise TypeError('the value to write must be of type float')
-        protocol, pins = self.xml_reader.get_port(device_name)
-        if not protocol == "AO" or "DO":
-            raise ValueError("you cannot write to device %s" % device_name)
+
+        port_info = self.xml_reader.get_port(device_name)
+        protocol = port_info["protocol"]
+        pins = port_info["pins"]
+
         for pin in self.xml_reader.get_port(device_name)["pins"]:
-            GPIO.write(self.Pin(pin,value))
\ No newline at end of file
+            if protocol == "DO":
+                #type check input value
+                if not value in [GPIO.HIGH,GPIO.LOW]:
+                    raise ValueError("value must be GPIO.HIGH or GPIO.LOW")
+                GPIO.output(self.Pin[pin].value,value)
+                return value
+            else: #throw error for protocols without write functionality
+                raise ValueError("you cannot write to device %s" % device_name)
+
+
+# ##test
+# interface_handler = Interface_handler(Xml_reader('XML/config.xml','XML/config.xsd'))
+# print(interface_handler.read('example'))
+# print(interface_handler.read('sensorarray'))
+# print(interface_handler.write('example',"test")) #shuld throw not writable error
\ No newline at end of file
diff --git a/xml_reader.py b/xml_reader.py
index bc79990..bfdcab1 100644
--- a/xml_reader.py
+++ b/xml_reader.py
@@ -2,7 +2,7 @@ from lxml import etree
 class Xml_reader:
     """ reader for the XML configuration """
 
-    def __init__(self, xml_path:str, xsd_path:str):
+    def __init__(self, xml_path: str, xsd_path: str):
         """inits the reader
 
         Args:
@@ -17,7 +17,7 @@ class Xml_reader:
             raise SyntaxError('the XML config file has an invalid syntax')
         self.root = etree.parse(xml_path).getroot()
 
-    def validate(self, xml_path:str, xsd_path: str) -> bool:
+    def validate(self, xml_path: str, xsd_path: str) -> bool:
         """validates a XML by using a XSD file
 
         Args:
@@ -38,7 +38,7 @@ class Xml_reader:
         """
         return [device.get("name") for device in self.root.findall('Device')]
 
-    def get_value_info(self,device_name:str) -> dict:
+    def get_value_info(self,device_name: str) -> dict:
         """returns the value information for a given device
 
         Args:
@@ -88,4 +88,12 @@ class Xml_reader:
                     "Device[@name='%s']/Port/Pin" % device_name
                     )
                 ]
-        }
\ No newline at end of file
+        }
+
+# ##test
+# xml_reader = Xml_reader('XML/config.xml','XML/config.xsd')
+# print(xml_reader.get_device_names)
+# print(xml_reader.get_value_info("example"))
+# print(xml_reader.get_port("example"))
+# print(xml_reader.get_value_info("sensorarray"))
+# print(xml_reader.get_port("sensorarray"))
\ No newline at end of file