In stead of assigning 0 directly to a timestamp member, make it None, then check whether it exists before doing the subtraction. This way, we can potentially use other types for the timestamp, as long as subtracting two of them result in an integer/float (meaning seconds).

Author: Sandyman

canopen/pdo/base.py

@@ -174,7 +174,7 @@ def __init__(self, pdo_node, com_record, map_array):
         #: Current message data
         self.data = bytearray()
         #: Timestamp of last received message
-        self.timestamp = 0
+        self.timestamp = None
         #: Period of receive message transmission in seconds
         self.period = None
         self.callbacks = []
@@ -268,7 +268,7 @@ def on_message(self, can_id, data, timestamp):
             with self.receive_condition:
                 self.is_received = True
                 self.data = data
-                self.period = timestamp - self.timestamp
+                self.period = timestamp - self.timestamp if self.timestamp is not None else timestamp
                 self.timestamp = timestamp
                 self.receive_condition.notify_all()
                 for callback in self.callbacks: