CN102882753A - Controller area network (CAN) message long delay processing method - Google Patents

Abstract

The invention discloses a long-delay processing method for CAN messages, aiming to solve the technical problems existing in the prior art that low-priority message sending difficulties affect real-time performance and artificially reducing the number of messages affects the full play of vehicle control functions, etc., and provides a method A CAN message long-delay processing method, which can automatically reduce the message ID when the delay time reaches the maximum delay that the sent message can bear when the network is busy, and send the message with a higher priority, improving the efficiency of sending the message Real-time, the method includes the following steps: start message sending; start timing; judge the message type; if it is a periodic message, if it is not successfully sent within the prescribed delay period, then reduce the message ID to resend; if it is an event message, If the message is not successfully sent within the specified time, the message ID will be lowered and resent.

Description

A CAN message long-delay processing method

technical field

The invention relates to the technical field of automobile electronic control, in particular to a method for processing long-delayed messages in the automobile CAN bus.

Background technique

In the CAN bus, the ID of each message is generally determined in advance. The priority strategy of the CAN bus is to determine the priority of sending messages according to the size of the ID value, and the smaller the ID value, the higher the priority. This will lead to a gradual increase in the transmission delay of some signals with low ID priority when the network is busy, so that they cannot be sent out for a long time, affecting the real-time performance of the control function.

The patent document whose publication date is April 27, 2011 and whose publication number is CN102035707A discloses a technical solution: a method for ensuring real-time communication of vehicle-mounted CAN networks. Is it greater than the sum of the number S1 of periodic messages to be sent and the reserved number S2 of event messages? If not, optimize the number of periodic messages sent by the electronic control unit until the greater than condition is satisfied. If greater, then according to the identifier ID assigns periodical messages to the time slots of the reference period, and reserves them for event messages to generate a message schedule; finally selects an electronic control unit as the timing reference node of the CAN network, and broadcasts the start message of the reference period in the reference period , each electronic control unit sends a periodic message according to the message scheduling table after receiving the reference period start message. The use of the existing CAN bus is guaranteed from the time sequence, so that the messages sent by each electronic control unit can be sent out in real time, so that the real-time communication of the vehicle CAN network is guaranteed. However, the disadvantage of this solution is that when the number of messages to be transmitted is relatively large, the number of messages must be reduced if the maximum number of messages S is exceeded. This is difficult to implement in today's environment where the number of vehicle network nodes is increasing and the number of messages is large. It is very difficult, and because the number of messages is limited, it affects the full performance of vehicle control functions.

Contents of the invention

The present invention mainly solves the technical problems existing in the prior art that low-priority message sending difficulties affect real-time performance and artificially reducing the number of messages affects the full play of vehicle control functions, and provides a long-delay processing method for CAN messages, which can be used as When the network is busy, when the delay time reaches the maximum delay that the sent message can bear, the message ID will be automatically reduced, and the priority of the message will be increased before sending out to improve the real-time performance of sending messages. This solution is easy to implement, low in cost, and easy to use The effect is good.

The present invention mainly solves the problems in the prior art through the following technical solutions, a CAN message long-delay processing method, which is a CAN network node that performs special processing on long-delay messages so that this type of message is processed when the network is busy. A method that can also be sent out according to a specified time, the method includes the following steps:

(A) initiate message sending;

(B) start the timer;

(C) Determine the message type;

(D) If it is a periodic message, if it is not successfully sent within the specified delay period, the message ID will be lowered and resent;

(E) If it is an event message, if it is not successfully sent within the specified time, the message ID will be lowered and resent.

Since message priority is tied to ID, messages with higher priority have smaller IDs.

The ID of the message is the identifier of the message, including information such as message priority and node address.

Because when the network is busy, the CAN bus will transmit a large number of messages, the messages with high priority will be sent first, so that the messages with low priority will be delayed. This method automatically calculates the delay time of the CAN message due to the busy network through the node timing after sending the message. When the delay time reaches the maximum delay that the sent message can bear (the specified delay period of the periodic message, event message specified duration), the node automatically reduces the message ID, so that the priority of the message is increased and sent out.

Preferably, a regular ID and a busy ID are configured for each message, and the message is sent using the busy ID after the delay reaches a specified time delay due to the busy network. The sending priority of the busy ID is high, and the busy ID can quickly occupy the CAN bus to send the message. The regular ID is used to send the message when the network is not busy.

Advantageously, the message resumes using the regular ID after the message has been sent using the busy ID. Restore the use of regular IDs to meet the design requirements when the CAN network is not busy. If the CAN network continues to be busy, judge the delay by timing, and use the busy ID to send again after the specified delay is reached again, and so on.

Preferably, the prescribed delay period is 3 regular sending periods, and the prescribed duration is 200 milliseconds. For periodic messages, the specified delay period is set to 3 times the normal sending period, and the specified duration of event messages is 200 milliseconds. In practice, such settings can better meet the load rate requirements of the CAN bus and low-priority messages. better real-time performance.

Preferably, when the message fails to be sent, the reduced message ID is used to resend. Reduce the ID of the message that failed to be sent, increase its priority and send it again.

Preferably, the reduced message ID is said busy ID. For the convenience of operation, the message that fails to be sent is sent directly using the busy ID.

The beneficial effect brought by the present invention is that when the network is busy, when the delay time reaches the maximum delay that the sent message can withstand, the message ID will be automatically reduced, and the priority of the message will be sent out, improving the efficiency of sending the message. Real-time, easy implementation of the scheme, low cost and good use effect.

Description of drawings

Fig. 1 is a flow chart of message processing in the present invention.

Detailed ways

The technical solution of the present invention will be further specifically described below through the embodiments and in conjunction with the accompanying drawings.

Embodiment: As shown in Figure 1, the present invention is a kind of CAN message long delay processing method, and this method comprises the following steps:

Step 101, configure a regular ID and a busy ID for each message in the network node. When the network is not busy, the message is sent using the regular ID, and when the network is busy and the delay in sending the message exceeds the specified delay, the message is sent using the busy ID. , the priority of the busy ID is higher than that of the regular ID;

Step 102, start message sending, and use the regular ID to send when sending;

Step 103, after the message is sent, the node starts a timer for the message and starts timing;

Step 104, judge the sent message, if it is a periodic message then go to step 106, if it is an event message then go to step 105;

Step 105, if the delay time of the event message is equal to or greater than 200 milliseconds and has not been successfully sent out, that is, it has not been successfully sent out when the specified duration is reached, then go to step 107;

Step 106, if the periodic message has not been successfully sent out after reaching 3 regular sending periods, that is, it has not been successfully sent out after reaching the specified delay period, then go to step 107;

Step 107, after the node automatically changes the message ID to a busy ID, the message can successfully occupy the CAN network and resend it;

Step 108, use the busy ID to resend the message, and restore the ID of the message to the regular ID after sending;

Step 109, check whether there is a message that failed to send, and repeat step 107 for the message that failed to send, after the node automatically changes the message ID to a busy ID, so that the message can successfully occupy the CAN network, resend, and then turn to step 108, Revert the message's ID back to the regular ID.

the

Therefore, the present invention has the ability to automatically change the message ID to the busy ID when the maximum delay time of the sent message reaches a specified value when the network is busy, and then use the busy ID to send the message that failed to send. Send out, improve the real-time performance of sending messages, the solution is easy to implement, low cost, good use effect and other characteristics.

Claims (6)

1. a CAN message long delay processing method is that a kind of CAN network node is processed especially to long delay message, and the method that this class message also can be sent when network is busy in required time is characterized in that the method may further comprise the steps:

(A) initiation message sends;

(B) beginning timing;

(C) judge type of message;

(D) if periodic message does not have successfully to send in the regulation delay cycle, then reduce message id and resend;

(E) if event message does not have successfully to send in the regulation duration, then reduce message id and resend.

2. described a kind of CAN message long delay processing method according to claim 1 is characterized in that: be each message arrangement one conventional ID, a busy ID delays when causing time-delay to reach regulation in that network is busy, and message uses busy ID to send.

3. described a kind of CAN message long delay processing method according to claim 2 is characterized in that: described message recovers to use described conventional ID after using busy ID to send to finish.

4. described a kind of CAN message long delay processing method according to claim 1, it is characterized in that: described regulation delay cycle is 3 conventional transmission cycles, and described regulation duration is 200 milliseconds.

5. described a kind of CAN message long delay processing method according to claim 1 and 2 is characterized in that: adopt the message id after reducing to resend when described message sends unsuccessfully.

6. described a kind of CAN message long delay processing method according to claim 5, it is characterized in that: the message id after the described reduction is described busy ID.

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