diff --git a/commands.py b/commands.py
index e7b8f9b..033ec58 100644
--- a/commands.py
+++ b/commands.py
@@ -135,6 +135,7 @@ def frappy(main=None, stick=None, addons=None):
     - frappy(''): the stick is removed too
     - addons are not changed when not given!
     """
+    all_cfg = {}
     if main is not None:
         all_cfg = frappy_start('main', main)
         if stick is None:
diff --git a/devices.py b/devices.py
index b75505b..c6d5caa 100644
--- a/devices.py
+++ b/devices.py
@@ -219,6 +219,9 @@ class FrappyNode(SecNodeDevice, Moveable):
     }
     parameters = {
         'service': Param('frappy service name (main, stick or addons)', type=str, default=''),
+        'param_category': Param("category of parameters\n\n"
+                                "set to 'general' if all parameters should appear in the datafile header",
+                                type=str, default='', settable=True),
     }
 
     _service_manager = FrappyManager()
@@ -237,6 +240,17 @@ class FrappyNode(SecNodeDevice, Moveable):
             self._cfgvalue = self._cache.get(self, 'value')
         return self._cfgvalue
 
+    def createDevices(self):
+        super().createDevices()
+        if self.param_category:
+            for devname, (_, devcfg) in self.setup_info.items():
+                params_cfg = devcfg['params_cfg']
+                dev = session.devices[devname]
+                for pname, pargs in params_cfg.items():
+                    pinfo = dev.parameters[pname]
+                    if not pinfo.category:
+                        pinfo.category = self.param_category
+
     @classmethod
     def config_dirs(cls, ins, service):
         sm = cls._service_manager