Systems and methods for implementing a time-stamped controller area network (CAN) bus message
Systems, methods, and apparatuses are provided herein for time-stamping a Controller Area Network (“CAN”) bus message. Control circuitry (e.g., of a network bridge) may receive a CAN message, and may, in response to receiving the CAN message, generate a time stamp. The control circuitry may add an entry to a lookup table stored in memory, wherein the entry correlates a CAN message Identifier (“ID”) corresponding to the CAN message with the time stamp. The control circuitry may encapsulate the CAN message and the time stamp, and may transmit the CAN message according to the time stamp.
1. A method for time-stamping a Controller Area Network (“CAN”) bus message, the method comprising:
receiving a CAN message at a network bridge;
in response to receiving the CAN message, generating a time stamp;
adding an entry to a lookup table stored in memory of the network bridge, wherein the entry correlates a CAN message Identifier (“ID”) corresponding to the CAN message with the time stamp;
determining that a message with the CAN message ID is to be transmitted over an Ethernet network;
determining the time stamp associated with the CAN message ID by looking up the CAN message ID in the lookup table;
scheduling the CAN message for transmission over the Ethernet network based on the time stamp; and
transmitting the CAN message over the Ethernet network according to the time stamp of the entry.
2. The method of claim 1 , wherein the time stamp indicates a time in which a Start-of-Frame (“SOF”) of the CAN message is received by the network bridge.
3. The method of claim 2 , wherein the method further comprises determining the CAN message ID by, in response to the network bridge receiving the SOF of the CAN message:
monitoring a CAN bus of the CAN for a CAN frame corresponding to the CAN message;
detecting, from the monitoring, the CAN frame; and
identifying the CAN message ID from an arbitration field of the CAN frame.
4. The method of claim 1 , wherein adding the entry to the lookup table comprises adding the entry to the lookup table in response to receiving a last bit of an End-of-Frame corresponding to the CAN message.
5. The method of claim 1 , wherein the lookup table comprises a finite amount of entries, wherein each entry of the finite amount of entries comprises an associated age, and wherein adding the entry to the lookup table comprises:
deleting an oldest entry in the lookup table;
increasing the age of each entry remaining in the lookup table; and
assigning the added entry an age that is youngest relative to each other entry of the lookup table.
6. The method of claim 1 , wherein generating the time stamp comprises adding an amount of latency to a time at which the CAN message is received.
7. The method of claim 1 , wherein determining the time stamp associated with the CAN message ID by looking up the CAN message ID in the lookup table comprises:
detecting, when looking up the CAN message ID in the lookup table, a plurality of entries that each correspond to the CAN message ID;
determining a time stamp for each entry of the plurality of entries; and
selecting the time stamp of the entry of the plurality of entries with a smallest corresponding age.
8. The method of claim 1 , wherein transmitting the CAN message according to the time stamp of the entry comprises:
packaging the time stamp and the CAN message into an Ethernet frame; and transmitting the Ethernet frame over the Ethernet network.
9. A system for time-stamping a Controller Area Network (“CAN”) bus message, the system comprising:
a network bridge comprising:
memory; and
control circuitry configured to:
receive a CAN message;
in response to receiving the CAN message, generate a time stamp;
add an entry to a lookup table stored in the memory of the network bridge, wherein the entry correlates a CAN message Identifier (“ID”) corresponding to the CAN message with the time stamp;
determine that a message with the CAN message ID is to be transmitted over an Ethernet network;
determine the time stamp associated with the CAN message ID by looking up the CAN message ID in the lookup table;
schedule the CAN message for transmission over the Ethernet network based on the time stamp; and
transmit the CAN message over the Ethernet network according to the time stamp of the entry.
10. The system of claim 9 , wherein the time stamp indicates a time in which a Start-of-Frame (“SOF”) of the CAN message is received by the network bridge.
11. The system of claim 10 , wherein the control circuitry is further configured to determine the CAN message ID by, in response to the network bridge receiving the SOF of the CAN message:
monitoring a CAN bus of the CAN for a CAN frame corresponding to the CAN message;
detecting, from the monitoring, the CAN frame; and
identifying the CAN message ID from an arbitration field of the CAN frame.
12. The system of claim 9 , wherein the control circuitry is further configured, when adding the entry to the lookup table, to add the entry to the lookup table in response to receiving a last bit of an End-of-Frame corresponding to the CAN message.
13. The system of claim 9 , wherein the lookup table comprises a finite amount of entries, wherein each entry of the finite amount of entries comprises an associated age, and wherein the control circuitry is further configured, when adding the entry to the lookup table, to:
delete an oldest entry in the lookup table;
increase the age of each entry remaining in the lookup table; and
assign the added entry an age that is youngest relative to each other entry of the lookup table.
14. The system of claim 9 , wherein the control circuitry is further configured, when generating the time stamp, to add an amount of latency to a time at which the CAN message is received.
15. The system of claim 9 , wherein the control circuitry is further configured, when determining the time stamp associated with the CAN message ID by looking up the CAN message ID in the lookup table, to:
detect, when looking up the CAN message ID in the lookup table, a plurality of entries that each correspond to the CAN message ID;
determine a time stamp for each entry of the plurality of entries; and
select the time stamp of the entry of the plurality of entries with a smallest corresponding age.
16. The system of claim 9 , wherein the control circuitry is further configured, when transmitting the CAN message according to the time stamp of the entry, to:
package the time stamp and the CAN message into an Ethernet frame; and
transmit the Ethernet frame over the Ethernet network.