GB2428113A

GB2428113A - Electronic timekeeping device using RDS signals

Info

Publication number: GB2428113A
Application number: GB0513909A
Authority: GB
Inventors: Brendon Willis Shaw
Original assignee: Visteon Global Technologies Inc
Current assignee: Visteon Global Technologies Inc
Priority date: 2005-07-07
Filing date: 2005-07-07
Publication date: 2007-01-17
Anticipated expiration: 2025-07-07
Also published as: GB2428113B; GB0513909D0

Abstract

The present invention relates to an electronic timekeeping device capable of decoding a broadcast Radio Data System (RDS) signal and selling an internal clock in response to the decoded RDS signal and to a method of using such a device. The apparatus (1) comprises a processor (18), a receiver (10), a decoder (10), and a clock (20,22). The receiver (10) receives in parallel or sequentially from an RDS broadcast system (6) a plurality of RDS signals (4). The decoder (10) decodes RDS time signals from the received RDS signals (4). The clock (20,22) generates an internal time signal (22). The processor (18) establishes from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable. The arrangement is such that the internal time signal (22) is reset using one or more of the RDS time signals that have been established to be reliable and not using those that have been established as being unreliable.

Description

Electronic Timekeeping Apparatus

BACKGROUND

a. Field of the Invention

The present invention relates to an electronic timekeeping device capable of decoding a broadcast Radio Data System (RDS) signal and setting an internal clock in response to the decoded RDS signal and to a method of using such a device.

b. Related Art Radio signals broadcast according to RDS standards include additional information in a frequency band outside the band(s) used to provide the audible portion of a broadcast. The information can include the name of the broadcast station or the programme being broadcast, the programme type, traffic service flags, and also the current time and date. In Europe, the RDS standard is called the RDS CENELEC standard. In North America the equivalent system is called RBDS and is defined by the NAB/EIA specification (a voluntary US industry standard). For convenience, these and equivalent systems will be referred to simply as "RDS".

A problem arises in that there is no guarantee that a radio transmitter will transmit the correct date or time (referred to hereinafter collectively and individually as "time"). If an electronic timekeeping device is tuned to receive an RDS signal in which the time is incorrect, then the incorrect time may be displayed to a user of the device, or used for some other purpose by other electronic devices leading to other inconveniences or problems.

It is an object of the present invention to provide a more reliable electronic timekeeping device for use with an RDS broadcast system.

SUMMARY OF THE INVENTION

According to the invention there is provided an electronic timekeeping apparatus for use with an RDS broadcast system, the apparatus comprising a processor, a receiver, a decoder, and a clock, wherein the receiver receives in parallel or sequentially from an RDS broadcast system a plurality of RDS signals, the decoder decodes a plurality of RDS time signals from said received RDS signals, the clock generates an internal time signal, the processor establishes from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable, the arrangement being such that the internal time signal is reset using one or more of the RDS time signals that have been established to be reliable and not using those that have been established as being unreliable.

Also according to the invention, there is provided a method of setting the time of an internal clock in an electronic timekeeping apparatus, the method comprising: - receiving in parallel or sequentially from an RDS broadcast system a plurality of RDS signals; - decoding a plurality of RDS time signals from said received RDS signals; - generating an internal time signal; - establishing from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable; - resetting the internal time signal using one or more of the RDS time signals that have been established to be reliable and not using those that have been established as being unreliable.

The receiver may be a radio receiver for receiving an RDS radio signal broadcast from a radio transmitter. The receiver may, alternatively be a receiver arranged to receive a broadcast signal from a coaxial or fibre optic cable transmission system, or any other type of communication system used for broadcasting an RDS signal.

The apparatus may also include a display for displaying the time to a user of the apparatus, for example a driver or other occupant of a motor vehicle when the apparatus is part of an in-vehicle entertainment system.

The processor may be a microprocessor chip, or may be formed from a number of discrete semiconductor components. Instructions for running the microprocessor may be encoded in software or firmware. Normally, the apparatus will comprise a memory, which may be provided integrally in the microprocessor. The processor or microprocessor may also provide the functionality for decoding the RDS signal, or this may be done as part of a radio receiver/tuner stage, and the person skilled in the art will recognise that other functions such as the internal clock can be provided within the same microprocessor or in a separate electronic component.

The receiver may be tuned or otherwise set to select any of a plurality of broadcast signals, for example automatically under the control of the processor or manually by a user of the device, or a combination of both manual selection and automatic tuning.

In one embodiment of the invention the processor is operable for a plurality of different RDS signals to: - compare each decoded time signal with the internal time signal; - record in the memory information regarding the degree of agreement between each decoded time signal and the internal time signal; - use said information regarding the degree of agreement to identify as reliable a plurality of RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - reset the internal time signal using one or more RDS time signals only if said RDS time signal or signals are in said identified group of reliable RDS time signals.

In another embodiment of the invention the processor is operable for a plurality of different RDS signals to: - compare each decoded time signal with at least one other decoded time signal; - record in the memory information regarding the degree of agreement between each decoded time signal and said at least one other decoded time signal; - use said information regarding the degree of agreement to identify as reliable a plurality of RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - reset the internal time signal using one or more RDS time signals only if said RDS time signal or signals are in said identified group of reliable RDS time signals.

It will often be the case that most RDS time signals will agree with each other to a high degree of accuracy, for example to within a few seconds. If there is an inaccuracy then it is likely that this will be considerably more, for example of the order of minutes, or even a full hour in the case of a broadcast which has not changed between summer and winter time. The apparatus is therefore preferably arranged to find a group of RDS time signals comprising at least half the total number of RDS time signals which closer agreement with each other than other group having the same number of RDS signals. These are then deemed to be reliable time signals. The remainder of the RDS time signals are then deemed to be unreliable time signals which will not be used to reset the internal time signal.

It is to be understood that, equivalently, the process of determining which signals are reliable which are not reliable could be approached from the opposite vantage point, namely identifying a group of RDS signals that do not agree well with each other, deeming these to be the unreliable signals and then defining the remainder to be reliable RDS signals.

The processor may be arranged to use the receiver to search automatically for all available RDS time signals in order to identify all available reliable RDS time signals. For example, the processor may identify one group consisting of all available RDS time signals each having a similar degree of agreement with the internal time signal.

In a preferred embodiment of the invention, the processor is also be operable to use the information regarding the degree of agreement to identify at least one additional group consisting of at least one RDS time signal, the processor being precluded from using an RDS time signal from said additional group to reset the internal time signal.

The degree of similarity required for an RDS time signal to belong to an identified reliable or unreliable group may be a pre-determined similarity measured, for example, in terms of seconds of time difference between time signals. The grouping may, however, be defined in other ways depending on the relative differences between each of the RDS time signals. It is therefore not necessary that the similarity of the degree of agreement be a predetermined criteria, but may be a calculated criteria that may vary according to the distribution pattern amongst the various RDS time signals as compared either with the internal time signal or amongst the various RDS time signals.

The similar degree of agreement amongst this identified group of RDS time signals establishes a consensus that RDS time signals from one group are reliable.

Therefore, if there is a difference between the internal time signal and one or more of the RDS time signals amongst this consensus grouping of RDS time signals, then the processor can safely reset the internal time signal. This resetting may be done in several ways. For example, the internal time signal may be reset to the RDS time signal whenever the tuneable receiver is set to receive an RDS time signal from amongst the identified reliable group of time signals and when there is a discrepancy between the internal time signal and the received RDS time signal.

Alternatively, the processor may use the tuner to capture a plurality of these reliable RDS time signals and then average or otherwise process these to form a consensus time signal which is then used to reset the internal time signal in preference to any of the individual reliable RDS time signals.

Preferably, the processor is operable to update the internal time signal automatically when the receiver is tuned to receive an RDS time signal that has been established to be reliable and when the there is a discrepancy between the internal time signal and said received RDS time signal.

The discrepancy may be any non-zero discrepancy, or it may be that the discrepancy has to be greater than a pre-determined non-zero amount before the internal time signal will be reset.

The internal time signal may be updated automatically to match the currently received reliable received RDS time signal.

Alternatively, the internal time signal may be updated automatically according to an average of a plurality of reliable received RDS time signals.

The decoder may additionally decode other information from the RDS signal, for example the broadcast station identity. The identity of a broadcast station may, however, be the broadcast frequency or wavelength of the station, as determined by the frequency at which the tuneable radio receiver is set.

The processor may be operable to record in the memory identification information regarding the identity of the broadcast source for each RDS signal, this information being linked to a record stored in said memory regarding the reliability of the corresponding RDS time signal.

For example, the processor may store together information regarding both the identity and the degree of agreement between each decoded time signal and the internal time signal. Usually the decoder will be operable to decode from an RDS signal the name of the broadcast source. The identification information is then the name of the broadcast source.

It is not necessary that the internal clock is reset if the discrepancy between the internal time signal and the reliable RDS time signal or signals is not great. For example if the discrepancy is less than one second, then there may be no need to correct the discrepancy. Therefore in general, the processor may postpone or defer resetting of the internal time signal if the decoded time signal agrees with the internal clock signal to within a predetermined accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a block schematic view of an electronic timekeeping apparatus according to one embodiment of the invention for use with an RDS broadcast system; and Figure 2 is a flow chart illustrating the main steps of a method according to one embodiment of the invention for setting the time of an internal clock in an electronic timekeeping apparatus.

DETAILED DESCRIPTION

Figure 1 is a block schematic view of an electronic timekeeping apparatus 1, having an antenna 2 which receives transmitted radio signals 4 from one or more radio transmitters 6. The received radio signals 8 carry a plurality of different encoded RDS signals each on a different broadcast frequency.

The antenna 2 provides the received radio signals 8 to a radio receiver and RDS decoder stage 10. For clarity, not shown are electronic stages for receiving and amplifying a transmitted audio programme and speakers for presenting the programme to a user of the apparatus 1. The receiver decoder 10 provides a decoded RDS signal 14 to a central processing unit (CPU) 16 of a microprocessor (pP) 18. The microprocessor 18 includes is connected to a crystal oscillator 20 which is used as a time base by the microprocessor 18. In this example, the CPU 16 divides the clock frequency in embedded firmware to provide an internal clock signal 22 within the microprocessor 18, which optionally includes also an internal year, month, day and day of the week.

In the present example, the receiver/decoder 10 is a tuneable radio receiver, for example an part of an in-vehicle entertainment system (not shown). A number of user input controls, indicated generally at 24, are used to control the operation of the apparatus I and provide a number of signals 26 to the CPU 16, including signals that are used by the CPU 16 to generate a tuning control signal 28 provided to the receiver/decoder 10. In this way the receiver/decoder 10 can be tuned both manually and under the control of the microprocessor 18.

The microprocessor 18 also includes a memory 22. In general the memory 22 will be comprise non-volatile random access memory circuits for storing changeable values, and also fixed or permanent memory circuits for storing fixed data or firmware.

An output signal 30 from the microprocessor 18 is provided to a display driver chip 32 which in turn provides display control signals 34 to a user display 36 on which is user information 38 is displayed, including the current time.

Reference is now made also to Figure 2, which illustrates a method 40 of using the apparatus I described above to set the time of the internal clock 22.

When the apparatus I is powered up 41, either for the first time or subsequently, the microprocessor 18 automatically causes the receiver/decoder 10 to scan 42 through all frequencies in a frequency band, for example the FM frequency band, searching for RDS signals. A test 42 is conducted by the microprocessor 18 to see if at least one RDS time signal has been decoded. If not, then the microprocessor 18 causes the display 36, 38 to show 49 the current internal time 22. In this context, "time" may include also the date. This time may have been free running from the last time the internal time was reset. Although not shown in Figure 2, if this is the very first time the apparatus has been powered on, or if power was lost causing the oscillator 20 to stop, resulting in a zero time value 22, the microprocessor 18 will cause a default initial time/date, such as 00:00 hours, I January 2005 to be displayed, which may be made to flash indicating that the current internal time 22 needs to be reset manually.

If at least one RDS time signal has been decoded, then the microprocessor 18 initially sets 44 the internal time signal 22 to the first received RDS time signal.

A test 45 is then conducted to see if more than one RDS time signal has been decoded, If not, then just the first decoded RDS time signal is used for the time display 49. If there has been more than one decoded RDS time signal, then the microprocessor sorts 46 the RDS time signals according to a detected variance in each RDS time signal with the internal time signal 22. In the case of the first received RDS time signal, this variance is zero. This value is stored in memory 22 together with information which identifies the first received signal 8, for example the signal frequency or wavelength as set by the receiver/decoder 10. In the case of the second and subsequent receiver RDS time signals, the time variance will in general be a non-zero time value, which is then also stored in memory 22 together with information, such as the broadcast frequency, which identifies each subsequent received signal 4.

The microprocessor 8 then establishes from the distribution of RDS time signals which are reliable and which are unreliable. In the special case of just two signals, it is not possible to establish that either signal is less reliable than the other, and so both are assumed to be reliable. For three and more signals, there are several ways in which the distribution can be assessed. One way in which this could be done for the number N received RDS time signals is to identify a group of (N+1)/2 RDS time signals having the minimum spread in terms of time between the slowest and fastest RDS time signals from amongst all groups of (N+1)/2 RDS time signals. - 10-

Other more sophisticated methods could be used to identify a group of signals most likely to be reliable. However, in the case of three received RDS time signals, this (N+1)12 approach would identify the two received RDS time signals which agreed most closely with one another. These would be deemed to be reliable time signals, and the third signal would be deemed to be unreliable.

Once a group of reliable RDS time signals has been identified, the internal time signal is reset 48 to an average of these reliable signals, and this time information 38 is then displayed 49 on the user display 36.

For consistency in subsequent use of the system, the initially detected time variances are then recalculated based on the reset internal time signal.

In use, the user could subsequently tune to a radio station to listen to one of the initially detected radio stations or a new station. The microprocessor 18 would then detect the RDS time signal and either refresh the previously detected time variance for that station or store in memory the newly detected time variance and the broadcast identity information for the newly received signal, and then recalculate and reset the internal time signal 22 in the same manner as described above using also the newly detected RDS time signal in this recalculation.

Although the invention has been described with reference to a radio wireless broadcast, the invention is equally applicable to any other system in which an RDS signal may be broadcast, for example a cable broadcast system.

The invention therefore provides a convenient way of resetting the time in an electronic timekeeping device when used with an RDS broadcast system. -11 -

Claims

CLAIMS: 1. An electronic timekeeping apparatus for use with an RDS

broadcast system, the apparatus comprising a processor, a receiver, a decoder, and a clock, wherein the receiver receives in parallel or sequentially from an RDS broadcast system a plurality of RDS signals, the decoder decodes a plurality of RDS time signals from said received RDS signals, the clock generates an internal time signal, the processor establishes from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable, the arrangement being such that the internal time signal is reset using one or more of the RDS time signals that have been established to be reliable and not using those that have been established as being unreliable.

2. An electronic timekeeping apparatus as claimed in Claim 1, the apparatus comprising a memory, wherein for a plurality of different RDS signals the processor is operable to: - compare each decoded time signal with the internal time signal; - record in the memory information regarding the degree of agreement between each decoded time signal and the internal time signal; - use said information regarding the degree of agreement to identify as reliable a plurality of RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - reset the internal time signal using one or more RDS time signals only if said RDS time signal or signals are in said identified group of reliable RDS time signals.

3. An electronic timekeeping apparatus as claimed in Claim 1, the apparatus comprising a memory, wherein for a plurality of different RDS signals the processor is operable to: - compare each decoded time signal with at least one other decoded time signal; - record in the memory information regarding the degree of agreement - 12- between each decoded time signal and said at least one other decoded time signal; - use said information regarding the degree of agreement to identify as reliable a plurality of RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - reset the internal time signal using one or more RDS time signals only if said RDS time signal or signals are in said identified group of reliable RDS time signals.

4. An electronic timekeeping apparatus as claimed in Claim 2 or Claim 3, in which the processor is operable to use said information regarding the degree of agreement to identify at least one additional group consisting of at least one RDS time signal, the processor being precluded from using an RDS time signal from said additional group to reset the internal time signal.

5. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is operable to update the internal time signal automatically when the receiver is tuned to receive an RDS time that has been established to be reliable and when the there is a discrepancy between the internal time signal and said received RDS time signal.

6. An electronic timekeeping apparatus as claimed in Claim 5, in which the internal time signal is updated automatically to match said reliable received RDS time signal.

7. An electronic timekeeping apparatus as claimed in Claim 5, in which the internal time signal is updated automatically according to an average of a plurality of reliable received RDS time signals.

8. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is arranged to use the receiver to search automatically for all available RDS time signals in order to identify all available reliable RDS time signals.

9. An electronic timekeeping apparatus as claimed in Claim 8, in which said processor is arranged to initiate said automatic search whenever the apparatus is first powered on.

10. An electronic timekeeping apparatus as claimed in any preceding claim, in which the apparatus includes a memory and the processor is operable to record in the memory identification information regarding the identity of the broadcast source for each RDS signal, said information being linked to a record stored in said memory regarding the reliability of the corresponding RDS time signal.

11. An electronic timekeeping apparatus as claimed in Claim 10, in which the receiver is a tuneable radio receiver, and the identification information is a broadcast frequency or wavelength.

12. An electronic timekeeping apparatus as claimed in Claim 10, in which the decoder is operable to decode from an RDS signal the name of the broadcast source, and the identification information is the name of the broadcast source.

13. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is arranged to postpone or defer resetting of the internal time signal if the decoded time signal agrees with the internal clock signal to within a predetermined accuracy.

14. A method of setting the time of an internal clock in an electronic timekeeping apparatus, the method comprising: - receiving in parallel or sequentially from an RDS broadcast system a plurality of RDS signals; decoding a plurality of RDS time signals from said received RDS signals; generating an internal time signal; - establishing from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable; - resetting the internal time signal using one or more of the RDS time signals that have been established to be reliable and not using those that have been established as being unreliable.

15. An electronic timekeeping apparatus for use with an RDS broadcast system, substantially as herein described, with reference to or as shown in the accompanying drawings.

16. A method of setting the time of an internal clock in an electronic timekeeping apparatus, substantially as herein described, with reference to or as shown in the accompanying drawings. 3'

Amendments to the claims have been filed as follows 1. An electronic timekeeping apparatus for use with an RDS broadcast system, the apparatus comprising a processor, a receiver, a decoder, a clock, and a memory, wherein the receiver receives in parallel or sequentially from an RDS broadcast system a plurality of RDS signals, the decoder decodes a plurality of RDS time signals from said received RDS signals, the clock generates an internal time signal, and the processor is operable to: compare each decoded time signal with at least one further time signal; record in the memory information regarding the degree of agreement between each decoded time signal and the at least one further time signal; - use said information regarding the degree of agreement to identify a first group coniprising a plurality of reliable RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - generate a reset time signal based upon one or more of the reliable time signals from the first group, and - compare the internal time signal with the reset time signal and if the internal time signal does not agree with the reset time signal to within a predetermined accuracy, reset the internal time signal using the reset time signal such that the internal time signal does agree with the reset time signal to within said predetermined accuracy.
2. An electronic timekeeping apparatus as claimed in Claim 1, wherein the at least one further time signal is the internal time signal.
3. An electronic timekeeping apparatus as claimed in Claim 1, wherein the processor is operable to: - compare each decoded time signal with at least one other decoded time signal; and - record in the memory information regarding the degree of agreement between each decoded time signal and said at least one other decoded time signal.
4. An electronic timekeeping apparatus as claimed in Claim 2 or Claim 3, in which the processor is operable to use said information regarding the degree of agreement to identify at least one additional group consisting of at least one RDS time signal, the processor being precluded from using an RDS time signal from said additional group to reset the internal time signal.
5. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is operable to update the internal time signal automatically when the receiver is tuned to receive an RDS time that has been established to be reliable and when the there is a discrepancy between the internal time signal and said received RDS time signal.
6. An electronic timekeeping apparatus as claimed in Claim 5, in which the internal time signal is updated automatically to match said reliable received RDS time signal.
7. An electronic timekeeping apparatus as claimed in Claim 5, in which the internal time signal is updated automatically according to an average of a plurality of reliable received RDS time signals.
8. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is arranged to use the receiver to search automatically for all available RDS time signals in order to identify all available reliable RDS time signals.
9. An electronic timekeeping apparatus as claimed in Claim 8, in which said processor is arranged to initiate said automatic search whenever the apparatus is first powered on.
10. An electronic timekeeping apparatus as claimed in any preceding claim, in which the apparatus includes a memory and the processor is operable to record in the memory identification information regarding the identity of the broadcast source for each RDS signal, said information being linked to a record stored in said memory regarding the reliability of the corresponding RDS time signal.
11. An electronic timekeeping apparatus as claimed in Claim 10, in which the receiver is a tuneable radio receiver, and the identification information is a broadcast frequency or wavelength.
12. An electronic timekeeping apparatus as claimed in Claim 10, in which the decoder is operable to decode from an RDS signal the name of the broadcast source, and the identification information is the name of the broadcast source.
13. An electronic timekeeping apparatus as claimed in any preceding claim, in which the processor is arranged to postpone or defer resetting of the internal time signal if the decoded time signal agrees with the internal clock signal to within a predetermined accuracy.
14. A method of setting the time of an internal clock in an electronic timekeeping apparatus, the method comprising: - receiving in parallel or sequentially from an RDS broadcast system a plurality of RDS signals; decoding a plurality of RDS time signals from said received RDS signals; generating an internal time signal; - establishing from the distribution of RDS time signals which RDS time signals are reliable and which are not reliable by comparing each decoded time signal with at least one further time signal and using the information regarding the degree of agreement to identify a first group comprising a plurality of reliable RDS time signals that are more closely grouped in time with respect to each other than with other RDS time signals; - generating a reset time signal based upon one or more of the reliable time signals from the first group; and - comparing the internal time signal with the reset time signal and if the tc internal time signal does not agree with the reset time signal to within a predetermined accuracy, resetting the internal time signal using the reset time signal such that the internal time signal does agree with the reset time signal to within said predetermined accuracy.
15. A method as claimed in Claim 14, wherein the at least one further time signal is the internal time signal.
16. A method as claimed in Claim 14, wherein the decoded time signal is compared with at least one other decoded time signal;
17. An electronic timekeeping apparatus for use with an RDS broadcast system, substantially as herein described, with reference to or as shown in the accompanying drawings.
18. A method of setting the time of an internal clock in an electronic timekeeping apparatus, substantially as herein described, with reference to or as shown in the accompanying drawings.