Support 11-bit identifiers in the serial interface (#1758)

Author: KB1RD

can/interfaces/serial/serial_can.py

@@ -135,7 +135,8 @@ def send(self, msg: Message, timeout: Optional[float] = None) -> None:
 
         # Pack arbitration ID
         try:
-            arbitration_id = struct.pack("<I", msg.arbitration_id)
+            arbitration_id = msg.arbitration_id + (0 if msg.is_extended_id else 0x20000000)
+            arbitration_id = struct.pack("<I", arbitration_id)
         except struct.error:
             raise ValueError(
                 f"Arbitration ID is out of range: {msg.arbitration_id}"
@@ -188,9 +189,15 @@ def _recv_internal(
 
                 s = self._ser.read(4)
                 arbitration_id = struct.unpack("<I", s)[0]
-                if arbitration_id >= 0x20000000:
+                is_extended_id = False if arbitration_id & 0x20000000 else True
+                arbitration_id -= 0 if is_extended_id else 0x20000000
+                if is_extended_id and arbitration_id >= 0x20000000:
                     raise ValueError(
-                        "received arbitration id may not exceed 2^29 (0x20000000)"
+                        "received arbitration id may not exceed or equal 2^29 (0x20000000) if extended"
+                    )
+                if not is_extended_id and arbitration_id >= 0x800:
+                    raise ValueError(
+                        "received arbitration id may not exceed or equal 2^11 (0x800) if not extended"
                     )
 
                 data = self._ser.read(dlc)
@@ -204,6 +211,7 @@ def _recv_internal(
                         arbitration_id=arbitration_id,
                         dlc=dlc,
                         data=data,
+                        is_extended_id=is_extended_id,
                     )
                     return msg, False
 

doc/interfaces/serial.rst

@@ -30,7 +30,9 @@ six parts. The start and the stop byte for the frame, the timestamp, DLC,
 arbitration ID and the payload. The payload has a variable length of between
 0 and 8 bytes, the other parts are fixed. Both, the timestamp and the
 arbitration ID will be interpreted as 4 byte unsigned integers. The DLC is
-also an unsigned integer with a length of 1 byte.
+also an unsigned integer with a length of 1 byte. Non-extended (11-bit)
+identifiers are encoded by adding 0x20000000 to the 11-bit ID. For example, an
+11-bit CAN ID of 0x123 is encoded with an arbitration ID of 0x20000123.
 
 Serial frame format
 ^^^^^^^^^^^^^^^^^^^
@@ -102,3 +104,21 @@ Examples of serial frames
 +================+=====================+======+=====================+==============+
 | 0xAA           | 0x66 0x73 0x00 0x00 | 0x00 | 0x01 0x00 0x00 0x00 | 0xBB         |
 +----------------+---------------------+------+---------------------+--------------+
+
+.. rubric:: CAN message with 0 byte payload with an 11-bit CAN ID
+
++----------------+---------+
+| CAN message              |
++----------------+---------+
+| Arbitration ID | Payload |
++================+=========+
+| 0x20000001 (1) | None    |
++----------------+---------+
+
++----------------+---------------------+------+---------------------+--------------+
+| Serial frame                                                                     |
++----------------+---------------------+------+---------------------+--------------+
+| Start of frame | Timestamp           | DLC  | Arbitration ID      | End of frame |
++================+=====================+======+=====================+==============+
+| 0xAA           | 0x66 0x73 0x00 0x00 | 0x00 | 0x01 0x00 0x00 0x20 | 0xBB         |
++----------------+---------------------+------+---------------------+--------------+

test/serial_test.py

@@ -86,7 +86,7 @@ def test_rx_tx_data_none(self):
 
     def test_rx_tx_min_id(self):
         """
-        Tests the transfer with the lowest arbitration id
+        Tests the transfer with the lowest extended arbitration id
         """
         msg = can.Message(arbitration_id=0)
         self.bus.send(msg)
@@ -95,13 +95,31 @@ def test_rx_tx_min_id(self):
 
     def test_rx_tx_max_id(self):
         """
-        Tests the transfer with the highest arbitration id
+        Tests the transfer with the highest extended arbitration id
         """
         msg = can.Message(arbitration_id=536870911)
         self.bus.send(msg)
         msg_receive = self.bus.recv()
         self.assertMessageEqual(msg, msg_receive)
 
+    def test_rx_tx_min_nonext_id(self):
+        """
+        Tests the transfer with the lowest non-extended arbitration id
+        """
+        msg = can.Message(arbitration_id=0x000, is_extended_id=False)
+        self.bus.send(msg)
+        msg_receive = self.bus.recv()
+        self.assertMessageEqual(msg, msg_receive)
+
+    def test_rx_tx_max_nonext_id(self):
+        """
+        Tests the transfer with the highest non-extended arbitration id
+        """
+        msg = can.Message(arbitration_id=0x7FF, is_extended_id=False)
+        self.bus.send(msg)
+        msg_receive = self.bus.recv()
+        self.assertMessageEqual(msg, msg_receive)
+
     def test_rx_tx_max_timestamp(self):
         """
         Tests the transfer with the highest possible timestamp