Protocol-tolerant communications in controller area networks
Systems and methods for protocol-tolerant communications in a Controller Area Network (CAN) are described. In some embodiments, a method may include receiving a frame at a network node; identifying, by the network node, a bit in a selected field of the frame; and determining, by the network node, that the frame follows a second format despite the bit indicating that the frame follows a first format. In other embodiments, a CAN controller includes message processing circuitry; and a memory coupled to the message processing circuitry, the memory having program instructions that configure the message processing circuit to: receive a frame; identify a bit in a selected field of the frame; and determine that the frame follows a Classical CAN format despite the bit indicating that the frame follows a flexible data-rate CAN (CAN FD) format.
1. A method, comprising:
receiving a frame at a network device, wherein the network device is compatible with frames in a first format and not in a second format;
inspecting one or more fields of the frame, by the network device, in response to a determination, by the network device, that an identified bit in a selected field of the frame indicates that the frame follows the second format; and
in response to the one or more fields of the frame matching fields expected of the second format, determining, by the network device, that the frame is in the second format, and ignoring the frame; and
in response to the one or more fields of the frame not matching the fields expected of the second format, determining, by the network device, that the identified bit is in error, and requesting re-transmission of the frame.
2. The method of claim 1 , wherein the network is a Controller Area Network (CAN) network.
3. The method of claim 2 , wherein the second format is a flexible data-rate CAN (CAN RD) format and wherein the first format is a Classical CAN format.
4. The method of claim 2 , wherein the selected field includes an FD format (FDF) bit of the frame.
5. The method of claim 2 , wherein the selected field includes a reserved (RES) bit of the frame.
6. The method of claim 1 , wherein determining that the frame follows the second format further includes matching the positions of the other fields within the frame to the positions of expected fields of frames following the second format.
7. The method of claim 1 , wherein the determining operation is part of a format exception procedure performed by the network device, and wherein the format exception procedure further includes stopping receipt of the frame and entering an integrating mode.
8. The method of claim 1 , further comprising an error frame in accordance with the second format in response to the frame containing an error, the error frame configured to trigger re-transmission of the frame.
9. A Controller Area Network (CAN) device comprising:
message processing circuitry; and
a memory coupled to the message processing circuitry, the memory having program instructions stored thereon that, upon execution by the message processing circuitry, configure the message processing circuit to:
receive a frame;
identify a bit in a selected field of the frame; and
determine that the frame follows a Classical CAN format despite the bit indicating that the frame follows a flexible data-rate CAN (CAN FD) format.
10. The CAN device of claim 9 , wherein the CAN device is not compatible with the CAN FD format and wherein the program instructions, upon execution by the message processing circuitry, further configure the message processing circuit to ignore the frame in response to the frame following the CAN FD format.
11. The CAN device of claim 9 , wherein the selected field includes at least one of: an FD format (FDF) bit of the frame or a reserved (RES) bit of the frame.
12. The CAN device of claim 9 , wherein determining that the frame follows the Classical CAN format further includes determining that the bit is in error.
13. The CAN device of claim 9 , wherein determining that the frame follows the Classical CAN format includes examining subsequent fields in the frame and matching the positions of the other fields within the frame to the positions of expected fields of frames following the Classical CAN format as opposed to the CAN FD format.
14. The CAN device of claim 9 , wherein the determining operation is part of a format exception procedure performed by the CAN device.
15. The CAN device of claim 9 , wherein the program instructions, upon execution by the message processing circuitry, further configure the message processing circuit to transmit an error frame in accordance with the Classical CAN format in response to the frame containing an error, the error frame configured to trigger re-transmission of the frame.
16. A Controller Area Network (CAN) network, comprising:
a CAN bus; and
a plurality of CAN devices coupled to the CAN bus, wherein a given one of the CAN devices is compatible with a Classical CAN format and incompatible with a flexible data-rate CAN (CAN FD) format, wherein the given CAN device is configured to ignore frames following the CAN FD format, and
wherein the given CAN device is further configured to:
receive a frame via the CAN bus;
identify an FD format (FDF) bit or a reserved (RES) bit within the frame; and
determine that the frame follows the Classical CAN format despite the bit indicating that the frame follows the CAN FD format.
17. The CAN network of claim 16 , wherein determining that the frame follows the Classical CAN format includes, as part of a format exception procedure, examining subsequent fields in the frame and matching the positions of the other fields within the frame to the positions of expected fields of frames if the frame followed the Classical CAN format as opposed to the CAN FD format.