The CAN interface Self Matching device of a kind of onboard diagnostic systemTechnical field
The invention belongs to the CAN technical field of onboard diagnostic system, it is specifically related to the CAN interface Self Matching device of a kind of onboard diagnostic system.
Background technology
Due to the mandatory requirement of Chinese law and regulations, the vehicle majority sold after 2008 has all installed automobile mounted diagnositc system. And the interface for diagnositc system, the electrical specification of its shape, part stitch is also defined by international standard ISO15031, as shown in table 1. Usually, onboard diagnostic system interface has 16 pin pins, and wherein stitch 6 and stitch 14 are respectively CAN_H and the CAN_L of CAN. But main frame factory or whole depot generally also can be used for realizing the self-defined function of some manufacturers at other CAN interface of pin deploy that producer is self-defined, as vehicle electronic control unit demarcation with write with a brush dipped in Chinese ink function. As 1 pin and 9 pin can be defined as CAN_H and the CAN_L of high-speed CAN bus by some producer respectively, for the demarcation that realizes vehicle electronic control unit with write with a brush dipped in Chinese ink. And the single line CAN that 1 pin can be defined as low speed by some producer is used for exporting car body component such as the information of car door, vehicle window, car light.
Table 1
Therefore, when on-vehicle information terminal or automobile fault diagnostic apparatus need to be connected by OBD interface and vehicle electronic control unit time, it is necessary to adopt corresponding switching wire harness could realize the self-defined function of the manufacturer except the universal diagnostic function of law regulation justice according to the definition of manufacturer. These functions comprise the DATA REASONING calibrating function such as vehicle electronic control unit, the program of vehicle electronic control unit or the upgrade function of data, the information output function etc. that manufacturer specifies. CN202759130 just gives the design of a kind of line of transferring for the OBD interface of specific main frame factory, and this switching line can only be used for specific vehicle certainly.
Based on the problems referred to above, the present invention provides the CAN interface Self Matching device of a kind of onboard diagnostic system, the self-defined stitch state of manufacturer of OBD interface can be detected, identify the deployment scheme of wherein CAN, and automatically set up the electrical connection of CAN data interface except law regulation justice (6 pin and 14 pin) of on-vehicle information terminal or automobile fault diagnostic apparatus and automobile mounted diagnositc system (OBD).
Summary of the invention
The present invention provides the CAN interface Self Matching device of a kind of onboard diagnostic system, to solve the problem of the CAN identification on the self-defined stitch of manufacturer and connection in onboard diagnostic system (OBD) interface in above-mentioned background technology.
The technical problem that the present invention solves is realized by following scheme:
A CAN interface Self Matching device for onboard diagnostic system, comprising: No. 18 select the multiplexed device 1, No. 28 of 1 select 1 multiplexed device 2, analog-to-digital conversion device 3, No. 1 two channels 4 select 1 multiplexed device 4, high-speed CAN transceiver 5, low speed CAN transceiver 6, single line CAN transceiver 7, No. 2 two channels 4 to select 1 multiplexed device 8, microprocessor 9;
In described onboard diagnostic system (OBD) interface 7 self-defined pins of producer by described No. 18 select 1 multiplexed device 1 and No. 28 select the multiplexed device 2 of 1 to be connected to described analog-to-digital conversion device 3 and described No. 1 two channels 4 selects the multichannel multiple 4 of 1 with on device;
The signal that described two 8 can be selected 1 multiplexed device 1,2 device to export by described road analog-to-digital conversion device 3 is sampled, and the level signal of sampling can be transferred to described microprocessor 9 by the mode of communication and process;
Described two 8 signals selecting 1 multiplexed device 1,2 to export also can be exported to the 4 of described No. 2 two channels simultaneously and select on 1 multiplexed device 8, the 4 of described No. 2 two channels select 1 multiplexed device 8 to be connected with high-speed CAN transceiver 5, low speed CAN transceiver 6 and single line CAN transceiver 7,1 multiplexed device 1,2 and above-mentioned two two channels 4 are selected to select 1 multiplexed device 4,8 by above-mentioned two 8, it is possible to realize the connection of the arbitrary combination of 7 self-defined pins of producer and three kinds of transceivers 5,6,7 in onboard diagnostic system interface;
Described CAN transceiver 5,6,7 selects 1 multiplexed device 8 to be connected in the CAN module of microprocessor 9 by No. 2 two channels 4 further;
The path 1 of above-mentioned 4 multiplexed devices, 2, 4, 8 ports selected control by described microprocessor 9, by the path 1 of above-mentioned 4 multiplexed devices, 2, 4, the combination control of 8 can realize 7 self-defined lines of producer and three types CAN transceiver 5 on onboard diagnostic system interface, 6, the arbitrary combination of 7, and can finally be connected with the CAN module on microprocessor 9, judge the deployment scheme of CAN, automatically the electrical connection of CAN data interface except law regulation justice (6 pin and 14 pin) of on-vehicle information terminal or automobile fault diagnostic apparatus and automobile mounted diagnositc system is set up.
Useful effect
The useful effect of the present invention is:
The present invention provides the CAN interface Self Matching device of a kind of onboard diagnostic system, the self-defined stitch state of manufacturer of OBD interface can be detected, identify the deployment scheme of wherein CAN, and automatically set up the electrical connection of CAN data interface except law regulation justice (6 pin and 14 pin) of on-vehicle information terminal or automobile fault diagnostic apparatus and automobile mounted diagnositc system (OBD).
The present invention provides the CAN interface Self Matching device of a kind of onboard diagnostic system, under can automatically completing the different CAN deployment way situation of OBD interface, and the foundation of CAN path link, it is to increase the compatibility of on-vehicle information terminal or automobile fault diagnostic apparatus.
The present invention provides the CAN interface Self Matching device of a kind of onboard diagnostic system, it is possible to completes the trouble diagnosis to automobile fast, is conducive to the maintenance of vehicle, saves servicing time and cost.
Accompanying drawing explanation
Fig. 1 is the level nature curve of three types CAN.
Fig. 2 is the principle schematic of the present invention.
Select for No. 1-1 81 multiplexed device, No. 2-2 8 select 1 multiplexed device, 3-analog-to-digital conversion device, 4-1 two channels 4 select 1 multiplexed device, 5-high-speed CAN transceiver, 6-low speed CAN transceiver, 7-single line CAN transceiver, 8-2 two channels 4 to select 1 multiplexed device, 9-microprocessor.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described further:
Fig. 1 is the level nature of three types CAN
As can be seen from the figure, the level nature of three types CAN has obvious difference. A wherein single line CAN only data lines, its dominant bit level is about 4V recessive position level and is about 0V, and high-speed CAN and low speed CAN have two lines, are CAN_H and CAN_L respectively. For high-speed CAN bus, recessive position level CAN_H and CAN_L is all about 2.5V, and dominant bit level CAN_H is about 3.5V, and CAN_L is about 1.5V. For low speed CAN, recessive position level CAN_H is about 0V, and CAN_L is about 5V, and dominant bit level CAN_H is about 3.6V, and CAN_L is about 1.4V. Microprocessor is according to the level feature of above-mentioned three kinds of CAN, and assists to send testing CAN information, so that it may to distinguish three kinds of CAN.
Fig. 2 is the principle of work figure of the present invention, it is described with certain vehicle: the 1st pin of the OBD interface of this vehicle and the 9th pin are defined as CAN_H and CAN_L of high-speed CAN bus respectively, so when Microprocessor S3C44B0X No. 18 selects 1 multiplexed device to be connected to 1 pin of OBD interface, when selecting 9 pin that 1 multiplexed device is connected to OBD interface for No. 28, analog-to-digital conversion device is by gathering the level of these two pins, so illustrate that these two pins be CAN_H and CAN_L of high-speed CAN be respectively which pin uncertain are CAN_H if the level of two pins is all 2.5V, which pin is CAN_L. now microprocessor can be assumed a combination and send a test data with high-speed CAN transceiver, if bus level state correctly illustrates that current hypothesis combination is correct, otherwise illustrates that the combination assumed is wrong. according to this kind of method microprocessor namely it can be inferred that correct CAN interface and set up the communication link of CAN by controlling corresponding multi-path choice device.