Communication system having a can bus and a method for operating such a communication system

• US 9,832,038 B2
• Filed: 10/20/2008
• Issued: 11/28/2017
• Est. Priority Date: 10/26/2007
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Aue, Axel, Gruenewald, Martin
• Primary Examiner(s): Zaman, Faisal M
• Application Number:
  US12/674,960
• Publication Number:
  US 20110125940A1
• Time in Patent Office: 3,326 Days
• Field of Search: 710104, 710105, 710117, 710124, 710305, 710316, 710240-244, 701 29, 370360, 370362, 370364
• CPC Class Codes: H04L 12/40032 Details regarding a bus interface enhancer
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN

Abstract

A communication system and a method for operating a communication system, the communication system having a CAN bus and at least two devices connected with the aid of the CAN bus. Such a device has a CAN control unit, an asynchronous, serial communication (ASC) interface unit, and a switch. The CAN control unit is suitable for transmitting, in a first transmission mode, CAN data frames over the CAN bus with the aid of a first physical protocol. The asynchronous, serial communication interface unit or ASC interface unit is suitable for transmitting, in a second transmission mode, ASC data frames over the CAN bus with the aid of a second physical protocol. The switch is designed for switching over between the first transmission mode and the second transmission mode as a function of at least one agreement effective between the device and at least one other device.

Claims

1. A communication system, comprising:

a CAN bus; and

at least two devices connected using the CAN bus, at least one of the at least two devices including;

a) a CAN control unit configured to transmit, in a first transmission mode, CAN data frames over the CAN bus using a first physical protocol in a plurality of predefined TTCAN time windows occurring cyclically in a plurality of cycles;

b) an asynchronous, serial communication (ASC) interface unit configured to transmit, in a second transmission mode, ASC data frames over the CAN bus using a second physical protocol; and

c) a switch adapted to switch over between the first transmission mode and the second transmission mode as a function of an agreement, effective between the at least one of the at least two devices and at least one other of the at least two devices, of in which first predefined switching time window a predefined number of the devices switch from the first transmission mode to the second transmission mode and in which second predefined switching window the predefined number of the devices switch from the second transmission mode to the first transmission mode;

wherein;

the first and second predefined switching time windows occur cyclically according to the plurality of cycles in which the TTCAN time windows cyclically occur; and

the CAN control unit is configured to transmit the CAN data frames over the CAN bus in the first transmission mode using a first bus clock pulse, and the ASC interface unit is configured to transmit the ASC data frames over the CAN bus in the second transmission mode using a second bus clock pulse, the second bus clock pulse being higher than the first bus clock pulse.

2. The method as recited in claim 1, wherein the agreement specifies which of the devices has an exclusive transmission authorization in one or more of the subsequent time windows following the switch into the second transmission mode.

3. The communication system as recited in claim 1, wherein the second bus clock pulse is higher than the first bus clock pulse by a factor of between 2 and 10.

4. The communication system as recited in claim 3, wherein the factor is between 5 and 10.

5. The communication system as recited in claim 3, wherein the factor is between 8 and 10.

6. The communication system as recited in claim 1, wherein a CAN data frame and an ASC data frame each have a header part and a useful data part, the header part of the ASC data frame being smaller than the header part of the CAN data frame.

7. The communication system as recited in claim 6, wherein the header part of the ASC data frame is smaller than the header part of the CAN data frame by a factor of between 2 and 5.

8. The communication system as recited in claim 7, wherein the factor is between 3 and 5.

9. The communication system as recited in claim 7, wherein the factor is between 4 and 5.

10. The communication system as recited in claim 1, wherein the at least two devices connected using the CAN bus include:

i) a test device and at least one control device, or ii) at least two control devices.

11. A method for operating a communication system having a CAN bus and at least two devices using the CAN bus, comprising:

a) equipping at least one of the devices with a CAN control unit which is suitable for transmitting, in a first transmission mode, CAN data frames over the CAN bus using a first physical protocol in a plurality of predefined TTCAN time windows occurring cyclically in a plurality of cycles;

b) equipping at least one of the devices with an asynchronous, serial communication (ASC) interface unit, which is suitable for transmitting, in a second transmission mode, ASC data frames over the CAN bus using a second physical protocol; and

c) switching over a predefined number of devices between the first transmission mode and the second transmission mode as a function of an agreement, effective between the predefined number of devices, of in which first predefined switching time window the predefined number of the devices switch from the first transmission mode to the second transmission mode and in which second predefined switching window the predefined number of the devices switch from the second transmission mode to the first transmission mode, wherein the first and second predefined switching time windows occur cyclically according to the plurality of cycles in which the TTCAN time windows cyclically occur.

12. The method as recited in claim 11, wherein the agreement is, at least partially, part of a control program storable in at least one of the devices.

13. The method as recited in claim 11, wherein the agreement is, at least partially, a part of an agreement message transmissible over the CAN bus.

14. The method as recited in claim 11, wherein the second transmission mode is prioritized with respect to the first transmission mode.

15. The method as recited in claim 11, wherein a device transmitting in the second transmission mode is suitable using the second physical protocol to establish a point-to-point link or a point-to-multipoint link to a predefined number of receiving devices to prevent asymmetric delays on the CAN bus.

16. The method as recited in claim 11, wherein, in the second transmission mode, time windows in which at least one of the devices or the predefined number of the devices may transmit or receive are predefined for the transmission of ASC data frames.

17. The method as recited in claim 11, wherein the agreement specifies which of the devices has an exclusive transmission authorization in one or more of the subsequent time windows following the switch into the second transmission mode.

18. A communications method comprising:

switching, by a switching circuit, a first device between a first transmission mode and a second transmission mode as a function of an agreement, effective between the first device and a second device, of in which first predefined switching time window the first device switches from the first transmission mode to the second transmission mode and in which second predefined switching window the first device switches from the second transmission mode to the first transmission mode;

wherein the first device is configured such that;

when transmitting in the first transmission mode, a CAN control unit of the first device transmits CAN data frames over a CAN bus using a first bus clock pulse in a plurality of predefined TTCAN time windows occurring cyclically in a plurality of cycles, according to which cycles the first and second predefined switching time windows cyclically occur; and

when transmitting in the second transmission mode, an asynchronous, serial communication (ASC) interface unit of the first device transmits ASC data frames over the CAN bus using a second bus clock pulse that is higher than the first bus clock pulse.

19. The method as recited in claim 18, wherein the agreement specifies which of the devices has an exclusive transmission authorization in one or more of the subsequent time windows following the switch into the second transmission mode.