Data logging in a motor vehicle
The invention relates to a method for logging messages on a data bus and temporarily storing the sent messages in a cyclically overwritable volatile storing means. The temporarily stored messages can be examined in a targeted manner for attributes of interest by using a verification program. A storage of the temporarily stored messages in a non-volatile second storing means can be initiated by means of definable trigger events that, for example, are formed from individual or a number of attributes of the messages. To this end, the occurrence of the defined trigger event is determined by a monitoring unit, and the data content of the volatile storing means are subsequently transferred into the storage locations of the non-volatile storing means. The principal advantage achieved with the above method resides in the possibility of backtracking the bus traffic. The exchanged messages may be backtracked and thus provide for the possibility to determine from which process and from which control device was the error message sent on the bus. This assists in a decisive manner in the error-seeking in complex communications networks. By means of the backtracking of the error message or with the analysis as to which message has eventually triggered an error in the communications network, it may be ascertained which process is responsible for the error and which program step triggered it. The error-seeking in the software programming of complex control device combination is thereby decisively facilitated.
1. A method of reading messages which are sent over a data bus in a motor vehicle between electronic units, comprising:
providing at least one communications network based on at least one data bus to which several electronic units are connected by a bus interface,
connecting the communications network with an external data processing unit by at least one data interface,
storing of messages which were sent in the communications network in at least one cyclically overwritable, volatile storing means,
examining the messages stored in the volatile storing means for selected, parameterizable attributes with at least one monitoring unit having an executable program,
upon the occurrence of at least one definable trigger event, whose occurrence is monitored by the executable program, stopping the cyclical overwriting of the volatile storing means for at least as long until the data content of the volatile storing means is transferred to a second, non-volatile storing means.
2. The method as defined in claim 1 ,
wherein
the definable trigger event may be read or exchanged over the data interface of the communications network.
3. The method as defined in claim 1 ,
wherein
the parameterizable attributes may be read or exchanged over the data interface of the communications network.
4. The method as defined in claim 1 , including reading the data content of the non-volatile storing means, upon request by an external electronic data processing device, into the external electronic data processing device over the data interface of the communications network.
5. The method as defined in claim 1 , including forming the trigger event from a logic or time-related concatenation of the parameterizable attributes.
6. The method as defined in claim 1 ,
wherein
the data bus is a CAN bus and the data interface is a serial interface or a modem interface.
7. The method as defined in claim 6 ,
wherein
the modem interface is a mobile wireless interface based on the standards of SMS, GSM or GPRS.
8. The method as defined in claim 1 ,
wherein
the parameterizable attributes are CAN identifier, error bits, error codes or selected travel data of the motor vehicle.
9. The method as defined in claim 1 ,including defining and monitoring several trigger events.
10. The method as defined in claim 1 , including after occurrence of a trigger event, effecting a notification to an external data processing device concerning the occurrence of the event.
11. The method as defined in claim 10 , including reading the data content of the non-volatile storing means, after sending the notification, into an external electronic data processing device at the request thereof.