Method and apparatus to prevent a node device from transmitting an unallowable message onto a CAN bus
AssigneePalo Alto Research Center Incorporated
InventorMarc E. Mosko
Life of this patent
Estimating the term…
Abstract
A first bus interface is coupled to communicate with a first controller area network (CAN) bus. A second bus interface is coupled to communicate with a node device, the node device configured to communicate with a second CAN bus. A logic circuit is coupled between the first and second bus interfaces and is operable to monitor communications by the node device via the second bus interface. If the logic circuit determines that the node device is transmitting a message that is not allowed for the node device, it prevents the message from being transmitted onto the first CAN bus in response thereto.
Claims20
An apparatus, comprising:
- a first bus interface coupled to communicate with a first controller area network (CAN) bus;
- a second bus interface coupled to communicate with a node device, the node device configured to communicate with a second CAN bus;
- and
- a logic circuit coupled between the first and second bus interfaces, the logic circuit operable to:
- read each bit of a message sent from the node device via the second bus interface as each bit is transmitted onto the first CAN bus via the second CAN bus;
- during a first time quantum of a bit period of each bit, determine that a current bit of the message indicates that the message is not allowed for the node device;
- and before the current bit can be detected on the first CAN bus, prevent the current bit and subsequent bits of the message from being transmitted onto the first CAN bus in response thereto.
A method comprising:
- electrically coupling an apparatus to communicate with a first controller area network (CAN) bus via a first CAN bus interface;
- electrically coupling a node device to the apparatus via a second CAN bus interface of the apparatus that is electrically separable from the first CAN bus interface;
- read each bit of a message sent from the node device as each bit is transmitted onto the first CAN bus interface via the second CAN bus interface;
- during a first time quantum of a bit period of each bit, determining that a current bit of the message indicates that the message is not allowed for the node device;
- and
- before the current bit can be detected on the bus, preventing the current bit and subsequent bits of the message from being transmitted onto the first CAN bus in response thereto.
An apparatus, comprising:
- a transceiver interface circuit configured to selectively couple and decouple a node device from a controller area network (CAN) bus;
- and
- a logic circuit coupled to the transceiver interface circuit, the logic circuit operable to:
- detect an output signal of the node device during each bit of a message transmitted by the node device, each bit transmitted during a nominal bit time that starts with a SYNC segment;
- determine whether values of the output signal during the SYNC segment of each bit represents part of a disallowed message;
- and
- if any of the values of the output signal represent part of the disallowed message, float the transceiver interface to prevent further transmission of the disallowed message onto the CAN bus.
Dependencies are inferred from the claim text.