Controller area network active bus terminator

• US 7,855,573 B1
• Filed: 12/14/2009
• Issued: 12/21/2010
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: Caterpillar Trimble Control Technologies LLC
• Original Assignee: Caterpillar Trimble Control Technologies LLC
• Inventors: Yost, Jerald Wayne
• Primary Examiner(s): Tran; Anh Q
• Application Number:
  US12/637,333
• Time in Patent Office: 372 Days
• Field of Search: None
• US Class Current: 326/30
• CPC Class Codes: G06F 13/4086 Bus impedance matching, e.g. termination

Abstract

A terminator for a CAN bus includes an electronic relay and a termination impedance. The electronic relay has first and second control input conductors and switched output conductors. The electrical connection between the switched output conductors is normally closed. The first control input conductor is connected to the power conductor and the second control input conductor is connected to a fifth terminal of the first CAN bus connector. The termination impedance is connected in series at the end node of the CAN bus with the switched output conductors across the high data conductor and the low data conductor. By this arrangement, the termination impedance is effectively connected across the high data conductor and the low data conductor at the end node of the CAN bus until an extension of the CAN bus is plugged into the first CAN bus connector. When an extension of the CAN bus is plugged into the first CAN bus connector, the fifth terminal of the CAN bus connector is connected to the ground conductor. This actuates the relay and opens the switched output conductors.

Claims

1. A terminator for a CAN bus, said CAN bus including a power conductor, a ground conductor, a high data conductor, and a low data conductor, said CAN bus further including a first CAN bus connector at the end node of the CAN bus, permitting another CAN bus to be connected thereto, said power conductor connected to a first terminal of said first CAN bus connector, said ground conductor connected to a second terminal of said first CAN bus connector, said high data conductor connected to a third terminal of said first CAN bus connector, and said low data conductor connected to a fourth terminal of said first CAN bus connector, comprising:

an electronic relay having first and second control input conductors and switched output conductors, the electrical connection between said switched output conductors being normally closed, said first control input conductor being connected to said power conductor and said second control input conductor being connected to a fifth terminal of said first CAN bus connector, and

a termination impedance connected in series at the end node of the CAN bus with said switched output conductors across said high data conductor and said low data conductor, whereby said termination impedance is effectively connected across said high data conductor and said low data conductor at the end node of the CAN bus until an extension of said CAN bus is plugged into said first CAN bus connector, and whereby when an extension of said CAN bus is plugged into said first CAN bus connector, said fifth terminal of said CAN bus connector is connected to said ground conductor, thereby actuating said relay and opening said switched output conductors.

2. The terminator for a CAN bus according to claim 1, in which said electronic relay comprises a photoMOS relay circuit.

3. The terminator for a CAN bus according to claim 1, further comprising a CAN bus extension, said CAN bus extension having a second CAN bus connector to permit said CAN bus extension to be connected to said CAN bus at said end node.

4. The terminator for a CAN bus according to claim 3, in which said second CAN bus connector includes a wired electrical connection between the terminal which connects to said second terminal of said first CAN bus connector and the terminal which connects to said fifth terminal of said first CAN bus connector, whereby connecting said second CAN bus connector to said first CAN bus connector results in actuation of said electronic relay and disconnection of said termination impedance.

5. A data bus arrangement, comprising:

a CAN bus, said CAN bus including a power conductor, a ground conductor, a high data conductor, and a low data conductor, said CAN bus further including a first CAN bus connector at the end node of the CAN bus permitting a CAN bus extension to be connected thereto, said power conductor connected to a first terminal of said first CAN bus connector, said ground conductor connected to a second terminal of said first CAN bus connector, said high data conductor connected to a third terminal of said first CAN bus connector, and said low data conductor connected to a fourth terminal of said first CAN bus connector,

an electronic relay having first and second control input conductors and switched output conductors, the electrical connection between said switched output conductors being normally closed, said first control input conductor being connected to said power conductor and said second control input conductor being connected to a fifth terminal of said first CAN bus connector, and

a termination impedance connected in series at the end node of the CAN bus with said switched output conductors across said high data conductor and said low data conductor, whereby said termination impedance is effectively connected across said high data conductor and said low data conductor at the end node of the CAN bus until a CAN bus extension is plugged into said first CAN bus connector, and whereby when said CAN bus extension is plugged into said first CAN bus connector, said fifth terminal of said first CAN bus connector is connected to said ground conductor, thereby actuating said relay and opening said switched output conductors.

6. The data bus arrangement of claim 5, in which said electronic relay comprises a photoMOS relay circuit.

7. The data bus arrangement of claim 5, further comprising a CAN bus extension, said CAN bus extension having a second CAN bus connector to permit said CAN bus extension to be connected to said CAN bus at said end node.

8. The data bus arrangement of claim 7, in which said second CAN bus connector includes a wired electrical connection between the terminal which connects to said second terminal of said first CAN bus connector and the terminal which connects to said fifth terminal of said first CAN bus connector, whereby connecting said second CAN bus connector to said first CAN bus connector results in actuation of said electronic relay and disconnection of said termination impedance.

9. A data bus arrangement, comprising:

a bus including a power conductor, a ground conductor, a pair of data conductors, said bus further including a first bus connector at the end node of the bus permitting a bus extension to be connected thereto, said power conductor connected to a first terminal of said first bus connector, said ground conductor connected to a second terminal of said first bus connector, and said pair of data conductors connected to third and fourth terminals of said first bus connector,

an electronic relay having first and second control input conductors and switched output conductors, the electrical connection between said switched output conductors being normally closed, said first control input conductor being connected to said power conductor and said second control input conductor being connected to a fifth terminal of said first bus connector, and

a termination impedance connected in series at the end node of the bus with said switched output conductors across said pair of data conductors, whereby said termination impedance is effectively connected across said data conductors at the end node of the bus until a bus extension is plugged into said first bus connector, and whereby when said bus extension is plugged into said first bus connector, said fifth terminal of said first bus connector is connected to said ground conductor, thereby actuating said relay and opening said switched output conductors.

10. The data bus arrangement of claim 9, in which said electronic relay comprises a photoMOS relay circuit.

11. The data bus arrangement of claim 9, further comprising a bus extension, said bus extension having a second bus connector to permit said bus extension to be connected to said bus at said end node.

12. The data bus arrangement of claim 11, in which said second bus connector includes a wired electrical connection between the terminal which connects to said second terminal of said first bus connector and the terminal which connects to said fifth terminal of said first bus connector, whereby connecting said second bus connector to said first bus connector results in actuation of said electronic relay and disconnection of said termination impedance.

13. A method of providing a terminating impedance at the end node of a CAN bus, said CAN bus including a power conductor, a ground conductor, a high data conductor, and a low data conductor, said CAN bus further including a first CAN bus connector at the end node of the CAN bus permitting a CAN bus extension to be connected thereto, said power conductor connected to a first terminal of said first CAN bus connector, said ground conductor connected to a second terminal of said first CAN bus connector, said high data conductor connected to a third terminal of said first CAN bus connector, and said low data conductor connected to a fourth terminal of said first CAN bus connector, comprising the steps of:

providing an electronic relay having first and second control input conductors and switched output conductors, the electrical connection between said switched output conductors being normally closed, said first control input conductor being connected to said power conductor and said second control input conductor being connected to a fifth terminal of said first CAN bus connector,

providing a termination impedance connected in series at the end node of the CAN bus with said switched output conductors across said high data conductor and said low data conductor,

effectively connecting said termination impedance across said high data conductor and said low data conductor at the end node of the CAN bus when a CAN bus extension is not plugged into said first CAN bus connector, and

connecting said fifth terminal of said first CAN bus connector to said ground conductor when a CAN bus extension is plugged into said first CAN bus connector, thereby actuating said relay and opening said switched output conductors.

14. The method of providing a terminating impedance at the end node of a CAN bus according to claim 13, in which the step of providing an electronic relay comprises the step of providing a photoMOS relay circuit.

15. The method of providing a terminating impedance at the end node of a CAN bus according to claim 13, in which the step of connecting said fifth terminal of said first CAN bus connector to said ground conductor comprises the step of connecting a CAN bus extension to said CAN bus at said end node with a second CAN bus connector.

16. The method of providing a terminating impedance at the end node of a CAN bus according to claim 15, in which the step of connecting a CAN bus extension to said CAN bus at said end node with a second CAN bus connector comprises the step of providing a wired electrical connection between the terminal which connects to said second terminal of said first CAN bus connector and the terminal which connects to said fifth terminal of said first CAN bus connector, whereby connecting said second CAN bus connector to said first CAN bus connector results in actuation of said electronic relay and disconnection of said termination impedance.