Add support for loading DCF configuration to remote node (#427)

Handle PDO-related objects through the associated methods in the PdoBase class when initializing a RemoteNode from an ObjectDictionary with provided values (DCF file usually).  This avoids the locally cached mapping information to get out of sync with the PDO configuration parameters, and thus eliminates the need to read back those same objects.

The PdoBase.read() method must honor DCF-provided values for this purpose.  It previously only respected the OD default values when called with from_od=True.

Co-authored-by: André Colomb <[email protected]>

Author: meifonglow

canopen/node/remote.py

@@ -146,16 +146,23 @@ def load_configuration(self) -> None:
 
         Iterate through all objects in the Object Dictionary and download the
         values to the remote node via SDO.
-        Then, to avoid PDO mapping conflicts, read back (upload) the PDO
-        configuration via SDO.
+        To avoid PDO mapping conflicts, PDO-related objects are handled through
+        the methods :meth:`canopen.pdo.PdoBase.read` and
+        :meth:`canopen.pdo.PdoBase.save`.
 
-        :see-also: :meth:`canopen.pdo.PdoBase.read`
         """
+        # First apply PDO configuration from object dictionary
+        self.pdo.read(from_od=True)
+        self.pdo.save()
+
+        # Now apply all other records in object dictionary
         for obj in self.object_dictionary.values():
+            if 0x1400 <= obj.index < 0x1c00:
+                # Ignore PDO related objects
+                continue
             if isinstance(obj, ODRecord) or isinstance(obj, ODArray):
                 for subobj in obj.values():
                     if isinstance(subobj, ODVariable) and subobj.writable and (subobj.value is not None):
                         self.__load_configuration_helper(subobj.index, subobj.subindex, subobj.name, subobj.value)
             elif isinstance(obj, ODVariable) and obj.writable and (obj.value is not None):
                 self.__load_configuration_helper(obj.index, None, obj.name, obj.value)
-        self.pdo.read()  # reads the new configuration from the driver

canopen/pdo/base.py

@@ -320,11 +320,20 @@ def add_callback(self, callback: Callable[[PdoMap], None]) -> None:
         self.callbacks.append(callback)
 
     def read(self, from_od=False) -> None:
-        """Read PDO configuration for this map using SDO."""
+        """Read PDO configuration for this map.
+        
+        :param from_od:
+            Read using SDO if False, read from object dictionary if True.
+            When reading from object dictionary, if DCF populated a value, the
+            DCF value will be used, otherwise the EDS default will be used instead.
+        """
 
         def _raw_from(param):
             if from_od:
-                return param.od.default
+                if param.od.value is not None:
+                    return param.od.value
+                else:
+                    return param.od.default
             return param.raw
 
         cob_id = _raw_from(self.com_record[1])