Automatic bus management

• US 7,881,430 B2
• Filed: 07/28/2006
• Issued: 02/01/2011
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Coombs, Kevin Andrew
• Primary Examiner(s): Barnie; Rexford N
• Assistant Examiner(s): Hammond; Crystal L
• Application Number:
  US11/495,839
• Publication Number:
  US 20080024161A1
• Time in Patent Office: 1,649 Days
• Field of Search: 326/30, 326/86, 326/27, 326/26, 378/62, 327/170
• US Class Current: 378/62
• CPC Class Codes: H04L 12/40 Bus networks
• CPC Class Codes: H04L 12/40032 Details regarding a bus interface enhancer
• CPC Class Codes: H04L 12/40039 Details regarding the setting of the power status of a node according to activity on the bus
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 25/02 Details ; arrangements for supplying electrical power along data transmission lines systems for transmitting signals via power distribution lines H04B3/54
• CPC Class Codes: H04L 25/0298 Arrangement for terminating transmission lines

Abstract

A method includes providing a bus, and providing a means for testing the bus for proper termination resistance during normal operation of the bus.

Claims

1. An imaging system comprising:

an x-ray source configured to project a beam of x-rays toward an object to be scanned;

a detector configured to detect x-rays energy passing through the object;

a computer connected to the detector and configured to receive a detector output and reconstruct an image of the object from the detector output; and

a bus controlled by the computer and configured to allow communication between a pair of devices; and

a test circuit coupled to the bus and configured to monitor a termination resistance of the bus during operation of the bus, the test circuit comprising;

a voltage source configured to generate a static test voltage;

a test resistor coupled to the voltage source;

a pair of switches coupled to the voltage source and configured to couple the voltage source to the bus, the bus being coupled in series between the pair of switches; and

a test point coupled to the test resistor and configured to indicate a voltage in the test circuit.

2. The imaging system of claim 1 wherein the test circuit monitors a voltage at the test point.

3. The imaging system of claim 1 being configured to determine the termination resistance of the bus according to:

R₁∥

R₂=R₃(DC/V₀−

1),

where R₁∥

R₂ is the termination resistance value of the bus, R₃ is the resistance value of the test resistor, DC is a static test voltage level of the voltage source, and V₀ is a voltage level of the voltage at the test point.

4. The imaging system of claim 1 wherein the bus comprises a controller area network (CAN) bus.

5. The imaging system of claim 1 wherein the voltage source comprises a DC voltage source.

6. The imaging system of claim 1 wherein each of the pair of switches comprises one of a transistor and an opto-isolator.

7. The imaging system of claim 1 wherein the test circuit comprises one of an analog circuit and a digital measurement circuit.

8. The imaging system of claim 1 wherein the test circuit is configured to monitor the termination resistance of the bus in an automated fashion.

9. The imaging system of claim 1 being configured to identify a termination flaw in the bus based on the determined termination resistance of the bus, the termination flaw comprising one of an over termination state and an under termination state of the bus.

10. The imaging system of claim 1 being configured to:

determine if the termination flaw completely inhibits communication of the bus; and

turn off the bus if the termination flaw completely inhibits communication of the bus;

otherwise, operate the bus in a degraded mode.

11. The imaging system of claim 1 being configured to detect a low-resistance condition based on the determined termination resistance of the bus.

12. The imaging system of claim 1 being configured to wirelessly transmit the results of the termination test to a remote location.

13. An imaging system comprising:

an x-ray source configured to project a beam of x-rays toward an object to be scanned;

a detector configured to detect x-rays energy passing through the object; and

a computer connected to the detector and configured to receive a detector output and reconstruct an image of the object from the detector output; and

a controller area network (CAN) bus controlled by the computer and configured to allow communication between a pair of devices; and

a test circuit operationally coupled to the bus and configured to monitor a termination resistance of the bus during operation of the bus, the test circuit further comprising;

a voltage source configured to generate a static test voltage;

a test resistor coupled to the voltage source;

a pair of switches coupled to the voltage source and configured to couple the voltage source to the bus; and

a test point coupled to the test resistor and configured to indicate a voltage in the test circuit;

wherein the computer is configured to determine the termination resistance of the CAN bus based on the static test voltage, a voltage at the test point, and a resistance value of the test resistor.

14. The imaging system of claim 13 wherein the computer is configured to determine the termination resistance of the CAN bus according to:

R₁∥

R₂=R₃(DC/V₀−

1),

where R₁∥

R₂ is the termination resistance value of the bus, R₃ is the resistance value of the test resistor, DC is a static test voltage level of the voltage source, and V₀ is a voltage level of the voltage at the test point.

15. The imaging system of claim 13 wherein the computer is configured to identify a termination flaw in the CAN bus based on the determined termination resistance of the CAN bus, the termination flaw comprising one of an over termination state and an under termination state of the bus.

16. The imaging system of claim 13 wherein the computer is configured to:

turn off the CAN bus if the termination flaw is outside a pre-determined range; and

operate the bus in a degraded mode if the termination flaw is within the pre-determined range.

17. A method for determining a termination resistance of an imaging system bus comprising:

generating a static test voltage from a voltage source;

providing the test voltage across differential signals of an imaging system bus and across a test resistor, thereby providing a voltage divider;

measuring an output of the voltage divider;

converting the output of the voltage divider to a resistance value; and

determining a termination resistance of the imaging system bus based on the resistance value;

wherein determining the termination resistance of the imaging system bus comprises determining the termination resistance according to;

R₁∥

R₂=R₃(DC/V₀−

1),

where R₁∥

R₂ is the termination resistance value of the bus, R₃ is the resistance value of the test resistor, DC is a static test voltage level of the voltage source, and V₀ is a voltage level of the voltage at the test point.

18. The method of claim 17 further comprising monitoring a value of the termination resistance of the imaging system bus.

19. The method of claim 18 further comprising:

identifying a termination flaw in the imaging system bus based on the monitored termination resistance, the termination flaw comprising one of an over termination state and an under termination state of the bus;

determining if the termination flaw completely inhibits communication of the bus; and

turning off the bus if the termination flaw completely inhibits communication of the bus; and

operating the bus in a degraded mode bus if the termination flaw does not completely inhibit communication of the bus.

20. A method for determining a termination resistance of an imaging system bus comprising:

generating a static test voltage from a voltage source;

providing the test voltage across differential signals of an imaging system bus and across a test resistor, thereby providing a voltage divider;

measuring an output of the voltage divider;

converting the output of the voltage divider to a resistance value;

determining a termination resistance of the imaging system bus based on the resistance value;

monitoring a value of the termination resistance of the imaging system bus;

identifying a termination flaw in the imaging system bus based on the monitored termination resistance, the termination flaw comprising one of an over termination state and an under termination state of the bus;

determining if the termination flaw completely inhibits communication of the bus; and

turning off the bus if the termination flaw completely inhibits communication of the bus; and

operating the bus in a degraded mode bus if the termination flaw does not completely inhibit communication of the bus.