VARIABLE OSCILLATOR FOR GENERATING DIFFERENT FREQUENCIES IN A CONTROLLER AREA NETWORK

• US 20090063909A1
• Filed: 11/07/2008
• Published: 03/05/2009
• Est. Priority Date: 10/25/2004
• Status: Active Grant

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: TimeGalactic AB (Scimitar)
• Inventors: Lennartsson, Kent, Fredriksson, Lars-Berno
• Granted Patent: US 7,934,039 B2
• Time in Patent Office: Days
• US Class Current: 714/49
• CPC Class Codes: G06F 13/4291 using a clocked protocol
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 27/2335 using temporal properties of the received signal
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 43/0823 Errors, e.g. transmission errors
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps

Abstract

A device suitable for use as a module in a Controller Area Network (CAN) system with a bus or connection includes relatively simple and inexpensive components, including an oscillator that generates a number of different frequencies in response to directions from a microcomputer. A CAN Controller receiving the frequencies is connected to the bus via a transceiver. The device has utility for verification and validation work in association with a CAN system.

Claims

1. A device suitable for incorporation as a module in a CAN system having a bus connection, the device comprising:

a microcomputer;

an oscillator that generates a number of different frequencies in response to directions from the microcomputer;

a transceiver; and

a Controller Area Network (CAN) Controller coupled to the oscillator,

wherein the CAN controller is coupled to the bus connection via the transceiver and

wherein the oscillator that generates a number of different frequencies clocks for the CAN Controller and a reference frequency that is compared with the variable clock frequency and adapts the module to any CAN bit time.

2. The device of claim 1, wherein the device is operable with levels (zeros and ones) appearing on the bus connection and transitions between the levels.

3. The device of claim 1, wherein the CAN Controller comprises means for indicating, in iterative fashion together with the oscillator and the microprocessor, whether a detected level or a level transition represents an error frame or error flag, wherein the CAN Controller utilizes previously-known information about the function or construction of the CAN system and at least one of the number of different frequencies.

4. The device of claim 1, further comprising means for adapting a CAN module to a setting of bit time and oscillator frequency specified for a CAN system.

5. The device of claim 1, further comprising means for measuring deviations between bit times in messages generated by different modules connected to the bus.

6. The device of claim 1, wherein the number of different frequencies generated by the oscillator, in addition to clocking the CAN Controller, also clock a counter, and wherein the frequency of the oscillator is related to a reference frequency of the microprocessor.

7. The device of claim 6, wherein an internal oscillator is arranged to generate the reference frequency.

8. The device of claim 6, wherein the reference frequency is determined from a CAN message appearing on the bus.

9. The device of claim 1, further comprising means for working with active or passive functions relative to the bus connection and other modules that are connected to the bus connection.

10. The device of claim 1, wherein the CAN Controller is connected to the transceiver via a transmission connection (TX1) and a reception connection (RX1), and wherein the transceiver is coupled to the bus via a CAN High Connection and a CAN Low Connection.

11. The device of claim 9, wherein the microprocessor is arranged to set the transceiver for either an active or a passive function.

12. The device of claim 1, further comprising means for generating pulses and pulse trains that other modules connected to the bus interpret differently according to rules of the CAN system.

13. The device of claim 1, further comprising means for receiving pulse trains from other modules and determining, by means of the pulse trains, within which setting limits the a first module interprets the pulse trains as correct CAN messages according to rules of the CAN system, and thereby ascertain deviations of the respective transmitting modules from nominal setting values.

14. The device of claim 1, further comprising means for determining that a particular sample point is located within a certain time period of a bit time by the indication of an error flag due to a bit error.

15. The device of claim 1, wherein a required oscillator precision is less than a precision that is generally required in a data communication system including either a USB type or a CAN system type.

16. The device of claim 15, wherein a variable clock frequency of a first module is arranged to either be compared to a reference frequency obtained from a crystal oscillator, or obtained indirectly from a particular message on the CAN bus by measuring a number of clock cycles that the particular message takes up from Start Of Frame to an acknowledgement bit, and by comparison with a predetermined derived value.

17. The device of claim 1, further comprising means for validating limits for a frequency deviation by compiling a number of error frames as a function of frequency.

18. A device suitable for incorporation as a module in (Controller Area Network) CAN systems with a bus connection on which different signal configurations appear dependent upon transmission conditions, the device comprising:

an oscillator with an ability to emit different frequencies;

a CAN Controller connected to the bus connection via a transceiver, wherein the oscillator is adjustable to emit a frequency depending upon a respective one of the different a signal configurations.

19. A device for adapting a (Controller Area Network) CAN module to a CAN bit time on a bus connection to which the module is connected, wherein the module comprises a CAN Controller that interacts with a simple oscillator, wherein:

the simple oscillator is arranged to work with a variable clock frequency that clocks the CAN Controller, a unit generates a reference frequency that is compared to the variable clock frequency, a time resolution of parts of a nanosecond in the bit time per setting step is achieved, different bit times are achieved with a same frequency by changing a number of bit quanta (BTQ) in the bit, and generation of bits that have small differences between them are achieved in spite of the construction of the simple oscillator.