Protection system for a car radio

Abstract: Protection system for a car radio, in which a vehicle, in particular a motor vehicle, is provided with electric wiring (2), comprising a CAN network (7), consisting of a plurality of transmission lines (BUSES, 9), which communicate with a central control unit (12, BODY COMPUTER) and are designed to transfer control signals from and to control devices (14), which are connected to electrical users of the vehicle (6). A car radio (15) which is installed in the vehicle (1) is interfaced with the CAN network (7), in order to permit exchange of data with the said central control unit (BODY COMPUTER, 12), and to carry out anti-theft functions for the car radio itself.

Description: The present invention relates to a protection system for a car radio. The object of the present invention is to provide a system which discourages thefts of car radios. In particular, the object of the present invention , is to provide a car radio which can operate solely with a vehicle which is specifically designed to accept it. More particularly, the object of the present invention is to prevent functioning of a car radio which is stolen from a vehicle, and installed in another vehicle. For instance US-5,870,018 describes an automotive radio anti-theft device via multiple bus, according to the preamble of claim 1. The aforementioned object is achieved by the present invention, in that it relates to a protection system for a car radio of the type described in claim 1. The invention is now described with reference to the attached drawings, which illustrate a non-limiting embodiment, in which: figure 1 illustrates schematically a vehicle which is provided with a protection system for a car radio, which is produced according to the dictates of the present invention; figure 2 illustrates a first block diagram of the operations carried out by the protection system according to the present invention, for a car radio; and figure 3 illustrates a second block diagram of the operations carried out by the protection system according to the present invention, for a car radio. In figure 1, 1 indicates a vehicle as a whole, in particular a motor vehicle, which is provided with electric wiring 2, which is supplied by a battery 4 (shown schematically), and can supply to a plurality of electric users 6 of the vehicle. In particular, the electric wiring 2 comprises a CAN network 7 (of a known type), which consists of a plurality of transmission lines (BUSES) 9, which communicate with a central control unit 12 (BODY COMPUTER), and can transfer control signals from and to control devices 14, which are connected to the electric users 6. As is known, use of a CAN network permits efficient remote control of the electric users 6, since the commands which are supplied to the electric users 6 pass via the BUSES 9, which can have a considerable length, whereas power is supplied to the electric users 6 by electric wiring which has a limited length. This therefore eliminates the use of numerous, long electric power cables to transfer the commands to the electric users. According to the present invention, a car radio 15, which is installed in the vehicle 1, is interfaced with the CAN network 7, and can carry out a step of data exchange with the BODY COMPUTER 12, in order to carry out anti-theft functions, which are illustrated hereinafter by means of figures 2 and 3. The functions which are carried out by the car radio 15 during its normal operation are illustrated with particular reference to figure 2. In particular, the car radio 15 and the BODY COMPUTER 12 each contain in their interior, in a memory location (not shown), a univocal identification code, which is known as the EXCHANGE CODE. When the car radio has been switched on (block 100), including after the electric wiring 2 has been disconnected from the battery 4, and has subsequently been re-connected to the battery 4, a circuit (not shown), which is inside the car radio itself, creates a random number, which is known hereinafter as the TEST PATTERN (block 110, which follows block 100). Block 110 is followed by a block 120, which, via the CAN network 7, conveys the TEST PATTERN previously created, to the BODY COMPUTER 12. The BODY COMPUTER 12 receives the TEST PATTERN from the CAN network 9 (block 130), and encrypts this TEST PATTERN by means of algorithms of a known type, using the resident EXCHANGE CODE; this therefore generates a response signal, which is conveyed (block 140, which follows block 130) to the car radio 15, via the CAN network 7. If, within a pre-determined time, the car radio 15 does not receive the response signal from the BODY COMPUTER 12 (block 150), it remains locked, and will not permit entry even of an unlocking code (block 155). The car radio 15 encrypts the TEST PATTERN generated locally in the car radio (block 110) by means of the same algorithm used in the BODY COMPUTER, using the EXCHANGE CODE which is resident in the car radio; this therefore generates a local response signal, which, in the presence of a response signal received, is compared (block 160, which follows block 150) with the response signal obtained from the BODY COMPUTER, and received by the car radio (block 150). If the result of the comparison is positive (i.e. if the EXCHANGE CODE which is present in the car radio 15 coincides with the EXCHANGE CODE which is present in the BODY COMPUTER 12), the block 160 is followed by a block 170, which makes possible the normal functions of the car radio, otherwise (EXCHANGE CODE present in the car radio 15, which is different from the EXCHANGE CODE which is present in the BODY COMPUTER 12) the car radio is locked (block 180, which follows block 160), and a step of entry of an unlocking code can be activated (block 190, which follows block 180). Figure 3 illustrates a block diagram relative to the operations which are carried out by the car radio 15, after reaching block 190, which is dedicated to entry of an unlocking code. As previously stated, block 190 is reached when the identification code of the car radio 15 does not coincide with the identification code of the BODY COMPUTER 12; this situation occurs typically in the following cases: when the car radio 15 has been fitted on another car which is provided with a CAN network, since the new car radio contains a resident EXCHANGE CODE which is different from that which is present in the BODY COMPUTER; and after replacement (or RESETTING) of the BODY COMPUTER 12, since the BODY COMPUTER contains a resident EXCHANGE CODE which is different from that which was present in the BODY COMPUTER which was previously operating. In block 190 there is entry of an unlocking code (MASTER CODE), which is preferably, but not necessarily, entered by means of a numerical keypad (not shown), which is associated with the car radio 15. Block 190 is followed by a block 200, which checks the correctness of the unlocking code entered; if the result is positive (MASTER CODE entered and recognised as correct), block 200 is followed by a block 220, otherwise (MASTER CODE entered, but recognised as incorrect), block 200 is followed by a block 205, which locks the car radio for a time interval ΔT. Block 205 is followed by a block 210, which prolongs the length of the time interval ΔT; from block 210, there is return to block 200. By this means, when a car radio which has an EXCHANGE CODE which is different from that which is stored in the BODY COMPUTER is switched on, use of the car radio is inhibited (block 180), and an unlocking step is necessarily activated (block 190). When unsuccessful attempts to enter the unlocking code are repeated, the unlocking step leads to de-activation of the car radio for increasing successive time intervals (blocks 205 and 210). If the BODY COMPUTER does not yet contain an EXCHANGE CODE stored, the cycle starts from block 220, and an unlocking code is not requested. This takes place in correspondence with the step of initial installation of the car radio (at the end of the assembly line), and before the car radio is switched on. By means of a random generator of numbers, block 220 creates an EXCHANGE CODE, and is followed by a block 225, which creates a new TEST PATTERN. Block 225 is followed by a block 230, which conveys the TEST PATTERN created in the previous block to the BODY COMPUTER 12, via the CAN network 7. The TEST PATTERN is received from the BODY COMPUTER 12, which encrypts this TEST PATTERN (block 240) by means of algorithms of a known type, using a constant (and in particular not using the EXCHANGE CODE, which may not yet be present, or could be different from that which is associated with the car radio); this therefore generates a further response signal, which is conveyed (block 250, which follows block 240) to the car radio 15, via the CAN network 7. If, within a pre-determined time, the car radio 15 does not receive the response signal from the BODY COMPUTER 12, it remains locked, and does not permit entry even of an unlocking code. The car radio 15 encrypts the TEST PATTERN generated in the car radio (block 220), with the same algorithm used in the BODY COMPUTER, using the same constant as that used in the BODY COMPUTER; this therefore generates a further local response signal, which is compared (block 260) with the further response signal obtained from the BODY COMPUTER 12, and received from the car radio. If the signals coincide, a correct connection between the car radio 15 and the BODY COMPUTER 12, and satisfactory functioning of the BODY COMPUTER 12, are detected via the CAN network 7; in this case, block 260 is followed by a block 270, which, via the CAN network 7, conveys the EXCHANGE CODE of the car radio to the BODY COMPUTER 12, where it is stored (block 280) and subsequently used for the operations described by the block diagram in figure 2. In particular, block 280 is followed by a block 290, which conveys to the car radio confirmation of the storage, and activates the subsequent procedures for normal operation (block 170, which follows block 290). If the signals do not coincide, block 260 ends the procedures for entry and storage of a new EXCHANGE CODE, and the car radio continues to be locked. The foregoing description makes apparent the advantages of the present invention, since the car radio 15 automatically continues to be locked in the event of failure to connect to the CAN network (block 150 does not detect any response signal). If the car radio 15 is connected to the CAN network, but the EXCHANGE CODES present in the BODY COMPUTER 12 and in the car radio 15 do not coincide, the car radio continues to be locked, and can be unlocked only by entering the unlocking code (MASTER CODE). This therefore discourages thefts of car radios, since the latter can operate only in a car which is provided with a CAN network, and if a CAN network is present, they can operate only if the EXCHANGE CODES of the car radio and of the BODY COMPUTER coincide. Otherwise, the unlocking code must be entered. Furthermore, if the battery is disconnected from, and subsequently connected to, the electrical system of the vehicle, it is not necessary to re-enter the unlocking code, since comparison of the EXCHANGE CODES which are present in the BODY COMPUTER and in the car radio takes place automatically. This makes it possible to avoid re-entering the unlocking code after car maintenance work has been carried out, and thus to prevent the many disadvantages which are caused by loss of a code by the final user.

Claims: Protection system for a car radio, in which a vehicle, in particular a motor vehicle, is provided with electric wiring (2), comprising a CAN network (7), consisting of a plurality of transmission lines 9), which communicate with a central control unit (12) and can transfer control signals from and to control devices (14), which are connected to electrical users of the vehicle (6), whereby said car radio (15), which is installed in the vehicle (1), is interfaced with the CAN network (7), in order to permit exchange of data with the said central control unit (12), and to carry out an anti-theft function for the car radio itself, according to which functioning of the said car radio (15) is inhibited (155,180) if correct exchange of data (150,160) is lacking; the said car radio (15) being provided with a univocal identification code, and the said central control unit (12) is provided with a univocal identification code; the said car radio (15) being provided with means (150) which can detect data on the said CAN line, and means (160) for comparison, which, after data has been exchanged on the said CAN line (7), can compare data correlated to codes which are resident in the car radio and in the central control unit (12), in order to permit activation (170) of the car radio itself; characterised in that said car radio (15) comprises: random generator means (110), which can create a random number after the said car radio (15) has been switched on (100); transmission means (120), which can convey the said random number to the said central control unit (12), via the said CAN network (7); the said central control unit (12) comprising: reception means (130) for the said random number, which can encrypt the said random number by means of algorithms, using the said identification code, by generating a response signal which is conveyed (140) to the car radio (15) via the said CAN network (7); the said car radio (15) receiving (150) the said response signal; the said car radio (15) also being able to encrypt the said random number with the same algorithm used in the central control unit (12), and using the identification code which is resident in the car radio, in order to generate a local response signal; the said comparison means comparing (160) the said response signal obtained from the central control unit (12) with the said local response signal generated in the said car radio (15). System according to claim 1, characterised in that as a result of lack of correspondence between the data correlated to the codes which are resident in the car radio and in the central control unit (12), the said comparison means (160) select locking means (180,190), which can inhibit the functioning of the said car radio (15). System according to claim 1 or 2, characterised in that if the said means (150) which can detect data on the CAN network (7) detect the absence of a response signal obtained from the central control unit (12) to the car radio (15), locking means (155) are selected, which can inhibit the functioning of the said car radio (15), without permitting activation of a step of entry of an unlocking code. System according to claim 2, characterised in that the said locking means (180, 190) can permit introduction of an unlocking code ; the said locking means (180, 190) cooperate with second comparison means (200), which check the correctness of the unlocking code entered, and increase (210, 205) the time interval for de-activation of the car radio (15), as a result of entry of incorrect unlocking codes. System according to claim 4, characterised in that as a result of entry of a valid unlocking code the said locking means (180, 190) can activate means for creation (220) of an identification code, and means for storage (280) of the said identification code, inside the said control unit (12). System according to claim 5, characterised in that the said means for creation (220) of an identification code are selected automatically in correspondence with the step of initial installation of the car radio, and of initial switching on of the car radio. System according to claim 5 or claim 6, characterised in that it comprises: further random generator means (225), which can create a further random number), as a result of introduction of a valid unlocking code; transmission means (230), which can convey the said further random number to the said central control unit (12), via the said CAN network (7); the said central control unit (12) comprising: reception means (240) for the said further random number, which can encrypt the said random number by means of algorithms using a constant, and generating a further response signal which is conveyed (250) to the car radio (15) via the said CAN network (7); the said car radio (15) receiving (260) the further response signal; the said car radio (15) also being able to encrypt the said further random number, with the same algorithm used in the central control unit (12), and using the same constant resident in the control unit in order to generate a further local response signal; the said car radio (15) comprising further comparison means which can compare (260) the said further response signal obtained from the central control unit (12) with the said further local response signal generated in the said car radio (15), in order to permit activation of the said storage means (280) .

Inventors: FERRARIS VALTER, TARDIVO MICHELE, FERRARIS, VALTER, TARDIVO, MICHELE
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 2000
Main classification: B60R11
IPC codes: B60R11