From b133a4021d13c15f1e050d8599dd6b0241afa4c7 Mon Sep 17 00:00:00 2001
From: pankaj <0xpankaj@gmail.com>
Date: Fri, 25 Sep 2026 04:29:23 +0545
Subject: [PATCH] pdo: Write the entries of an ARRAY mapping in PdoMap.save()

save() sets sub-index 0 of the mapping to 0 and then iterates
self.map_array.values() to write the entries. For a mapping declared as an
ARRAY, map_array is an SdoArray whose length is uploaded from sub-index 0,
which was just set to 0, so no entry is written and only the count is.

Address the entries by the sub-indices the object dictionary defines
instead. RECORD mappings and the fixed-count workaround behave as before.
---
 canopen/pdo/base.py |  8 +++++++-
 test/test_pdo.py    | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/canopen/pdo/base.py b/canopen/pdo/base.py
index f9973882..7c899142 100644
--- a/canopen/pdo/base.py
+++ b/canopen/pdo/base.py
@@ -452,7 +452,13 @@ def _set_com_record(
             # mappings for an invalid object 0x0000:00 to overwrite any
             # excess entries with all-zeros.
             self._fill_map(self.map_array[0].raw)
-        for var, entry in zip(self.map, self.map_array.values()):
+        # Address the entries by the sub-indices the object dictionary defines:
+        # iterating the SDO array would ask the device for its entry count,
+        # which was just set to 0 above, and so write no entry at all.
+        entries = (
+            self.map_array[subindex] for subindex in self.map_array.od if subindex != 0
+        )
+        for var, entry in zip(self.map, entries):
             if not entry.od.writable:
                 continue
             logger.info(
diff --git a/test/test_pdo.py b/test/test_pdo.py
index 1b641147..85caff41 100644
--- a/test/test_pdo.py
+++ b/test/test_pdo.py
@@ -110,6 +110,41 @@ def test_pdo_save(self):
         self.node.tpdo.save()
         self.node.rpdo.save()
 
+    def test_pdo_save_writes_the_entries_of_an_array_mapping(self):
+        # A mapping declared as an ARRAY is sized by its sub-index 0, which
+        # save() sets to 0 before it writes the entries.
+        od = canopen.objectdictionary.ObjectDictionary()
+        comm = canopen.objectdictionary.ODRecord("TPDO 1 communication", 0x1800)
+        for subindex, data_type in ((0, canopen.objectdictionary.UNSIGNED8),
+                                    (1, canopen.objectdictionary.UNSIGNED32),
+                                    (2, canopen.objectdictionary.UNSIGNED8)):
+            var = canopen.objectdictionary.ODVariable(f"sub{subindex}", 0x1800, subindex)
+            var.data_type, var.access_type, var.default = data_type, "rw", 0
+            comm.add_member(var)
+        od.add_object(comm)
+        mapping = canopen.objectdictionary.ODArray("TPDO 1 mapping", 0x1A00)
+        for subindex in range(5):
+            var = canopen.objectdictionary.ODVariable(f"sub{subindex}", 0x1A00, subindex)
+            var.data_type = (canopen.objectdictionary.UNSIGNED8 if subindex == 0
+                             else canopen.objectdictionary.UNSIGNED32)
+            var.access_type, var.default = "rw", 0
+            mapping.add_member(var)
+        od.add_object(mapping)
+        for index, data_type in ((0x2001, canopen.objectdictionary.INTEGER16),
+                                 (0x2002, canopen.objectdictionary.UNSIGNED8)):
+            var = canopen.objectdictionary.ODVariable(f"value {index:X}", index)
+            var.data_type, var.access_type, var.pdo_mappable = data_type, "rw", True
+            od.add_object(var)
+        node = canopen.LocalNode(1, od)
+        pdo = node.tpdo[1]
+        pdo.add_variable(0x2001)
+        pdo.add_variable(0x2002, length=4)
+        pdo.cob_id = 0x181
+        pdo.save()
+        self.assertEqual(node.sdo.upload(0x1A00, 0), bytes([2]))
+        self.assertEqual(node.sdo.upload(0x1A00, 1), (0x20010010).to_bytes(4, "little"))
+        self.assertEqual(node.sdo.upload(0x1A00, 2), (0x20020004).to_bytes(4, "little"))
+
     def test_pdo_save_skip_readonly(self):
         """Expect no exception when a record entry is not writable."""
         # Saving only happens with a defined COB ID and for specified parameters