Controller area network (CAN) based communication system with multiple bus connected nodes

A communication system, comprising a plurality of bus-connected nodes, each node having a unique node ID, wherein, when a collision occurs between message packets transmitted from the nodes, a message packet with an arbitration field indicating a node ID with a highest priority flows through a bus ahead of any other colliding message packet, wherein each of the nodes comprises:

• a communication control circuit that controls communication to and from the node;
• and
• a communication interface circuit that transmits and receives a message packet, wherein the communication control circuit of the node:
• writes its own node ID as a transmitting node ID into an arbitration field of a message packet to be transmitted to the bus;
• writes a node ID of a destination node into an auxiliary field defined at a predetermined location in the message packet;
• transmits through the communication interface circuit to the bus the message packet in which the transmitting and destination node IDs are written;
• determines, based on a comparison between its on node ID and a node ID indicated in an arbitration field of a message packet existing on the bus, whether or not the message packet is to be received;
• and
• receives through the communication interface circuit a message packet that is determined to be received, wherein the communication system further comprises a control unit comprising:
• a communication control circuit that controls communication to and from the control unit;
• and
• a communication interface circuit that transmits and receives a message packet, wherein the communication control circuit of the control unit:
• receives through the communication interface circuit a message packet transmitted from one of the nodes;
• rewrites the received message packet by replacing a node ID written in the arbitration field with a node ID written in the auxiliary field;
• and
• transmits the rewritten message packet through the communication interface circuit to the bus.

A control unit that controls a flow of message packets through a bus, wherein a node ID uniquely defined for each of bus-connected nodes is indicated in an arbitration field of each message packet, the control unit comprising:

• a receiving unit that receives a message packet in which one of the nodes has written a node ID of a transmitting node in the arbitration field and has written a node ID of a destination node in an auxiliary field defined at a predetermined location;
• a rewriting unit that rewrites the received message packet by replacing the node ID written in the arbitration field with the node ID written in the auxiliary field;
• and
• a transmitting unit that transmits the rewritten message packet to the bus.

A control unit that controls a flow of message packets through a bus, wherein a node ID uniquely defined for each of bus-connected nodes is indicated in an arbitration field of each message packet, the control unit comprising:

• a communication control circuit that controls communication to and from the control unit;
• and
• a communication interface circuit that transmits and receives a message packet, wherein the communication control circuit:
• receives through the communication interface circuit a message packet in which one of the nodes has written a node ID of a transmitting node in the arbitration field and has written a node ID of a destination node in an auxiliary field defined at a predetermined location;
• rewrites the received message packet by replacing the node ID written in the arbitration field with the node ID written in the auxiliary field;
• and
• transmits the rewritten message packet through the communication interface circuit to the bus.

A CAN bus connected node, wherein, when the node detects presence of a colliding message packet while the node attempts to transmit a message packet to a bus, the node determines, based on a comparison between its own node ID and a node ID indicated in an arbitration field of the colliding message packet, whether or not the node continues to transmit its own message packet, the CAN bus connected node comprising:

• a transmitting node ID writing unit that writes its own node ID as a transmitting node ID into an arbitration field of a message packet to be transmitted to the bus;
• a destination node ID writing unit that writes a node ID of a destination node into an auxiliary field defined at a predetermined location in the message packet;
• a transmitting unit that transmits to the bus the message packet in which the transmitting and destination node IDs are written;
• a determination unit that determines, based on a comparison between its own node ID and a node ID indicated in an arbitration field of a message packet existing on the bus, whether or not the message packet is to be received;
• and
• a receiving unit that receives the message packet if the determination unit determines that the message packet is to be received.

A CAN bus connected node, comprising:

• a communication control circuit that controls communication to and from the node;
• and
• a communication interface circuit that transmits and receives a message packet, wherein, when the communication control circuit detects presence of a colliding message packet while the node attempts to transmit a message packet through the communication interface circuit to a bus, the communication control circuit determines, based on a comparison between its own node ID and a node ID indicated in an arbitration field of the colliding message packet, whether or not the node continues to transmit its own message packet, wherein the communication control circuit:
• writes its own node ID as a transmitting node ID into an arbitration field of a message packet to be transmitted to the bus;
• writes a node ID of a destination node into an auxiliary field defined at a predetermined location in the message packet;
• transmits through the communication interface circuit to the bus the message packet in which the transmitting and destination node IDs are written;
• determines, based on a comparison between its own node ID and a node ID indicated in an arbitration field of a message packet existing on the bus, whether or not the message packet is to be received;
• and
• receives through the communication interface circuit a message packet that is determined to be received.

A CAN bus communication method for use in a CAN bus system comprising a plurality of bus-connected nodes and a control unit that controls communication between the nodes, wherein one of the nodes performs the steps of:

• writing its own node ID as a transmitting node ID into an arbitration field of a message packet to be transmitted to a bus;
• writing a node ID of a destination node into an auxiliary field defined at a predetermined location in the message packet;
• and
• transmitting to the bus the message packet in which the transmitting and destination node IDs are written, and wherein the control unit performs the steps of:
• receiving the message packet transmitted from the node;
• rewriting the received message packet to generate a message packet in which the node ID written in the arbitration field is replaced with the node ID written in the auxiliary field;
• and
• transmitting the generated message packet to the bus.

A storage medium readable by a computer, the storage medium storing a program of instructions executable by the computer to perform a function for controlling a control unit that controls a flow of message packets through a bus, wherein a node ID uniquely defined for each of bus-connected nodes is indicated in an arbitration field of each message packet, the function comprising the steps of:

• receiving a message packet in which one of the nodes has written a node ID of a transmitting node in the arbitration field and has written a node ID of a destination node in an auxiliary field defined at a predetermined location;
• rewriting the received message packet by replacing the node ID written in the arbitration field with the node ID written in the auxiliary field;
• and
• transmitting the rewritten message packet to the bus.

A storage medium readable by a computer, the storage medium storing a program of instructions executable by the computer to perform a function for controlling a CAN bus connected node, wherein, when the node detects presence of a colliding message packet while the node attempts to transmit a message packet to a bus, the node determines, based on a comparison between its own node ID and a node ID indicated in an arbitration field of the colliding message packet, whether or not the node continues to transmit its own message packet, the function comprising the steps of:

• writing its own node ID as a transmitting node ID into an arbitration field of a message packet to be transmitted to the bus;
• writing a node ID of a destination node into an auxiliary field defined at a predetermined location in the message packet;
• transmitting to the bus the message packet in which the transmitting and destination node IDs are written;
• determining, based on a comparison between its own node ID and a node ID indicated in an arbitration field of a message packet existing on the bus, whether or not the message packet is to be received;
• and
• receiving the message packet if the message packet is determined to be received.