Support PDO lookup by communication parameter record index.

Store each PDO under two different index numbers in the dummy PdoMaps
object's "maps" attribute.  That would duplicate them in sequential
access while iterating / counting though, so override the PdoBase
dunder methods to explicitly chain just the two sub-sequences rx and
tx.

Author: acolomb

canopen/pdo/__init__.py

@@ -1,4 +1,6 @@
+import itertools
 import logging
+from collections.abc import Iterator
 
 from canopen import node
 from canopen.pdo.base import PdoBase, PdoMap, PdoMaps, PdoVariable
@@ -35,8 +37,16 @@ def __init__(self, node, rpdo: PdoBase, tpdo: PdoBase):
         # The object 0x1A00 equals to key '1' so we remove 1 from the key
         for key, value in self.rx.items():
             self.map.maps[self.rx.map_offset + (key - 1)] = value
+            self.map.maps[self.rx.com_offset + (key - 1)] = value
         for key, value in self.tx.items():
             self.map.maps[self.tx.map_offset + (key - 1)] = value
+            self.map.maps[self.tx.com_offset + (key - 1)] = value
+
+    def __iter__(self) -> Iterator[int]:
+        return itertools.chain(self.rx, self.tx)
+
+    def __len__(self) -> int:
+        return len(self.rx) + len(self.tx)
 
 
 class RPDO(PdoBase):

test/test_pdo.py

@@ -55,6 +55,7 @@ def test_pdo_getitem(self):
         self.assertEqual(by_mapping_record['INTEGER16 value'].raw, -3)
         self.assertIs(node.tpdo[0x1A00], by_mapping_record)
         self.assertIs(node.tpdo[0x1800], by_mapping_record)
+        self.assertIs(node.pdo[0x1800], by_mapping_record)
         by_object_name = node.pdo['INTEGER16 value']
         self.assertIsInstance(by_object_name, canopen.pdo.PdoVariable)
         self.assertIs(by_object_name.od, node.object_dictionary['INTEGER16 value'])