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Front and rear Tbox and OBD interact with CAN bus

Release date:2021-12-28Author source:KinghelmViews:228

T-box is a front mounted, telematic box, that is, there is a networked controller in the vehicle before the vehicle is put on the market. The corresponding mobile phone app will be released on the vehicle, and the following functions can be realized through the mobile phone app normally:


Remote control vehicle: door unlocking, window control, skylight control, air conditioning control, vehicle start and other functions;


Obtain vehicle information: door status, window status, lamp status, tire pressure status, vehicle fault information, vehicle positioning and other functions;


Security service: alarm when the vehicle is towed away, remote alarm and location tracking after the vehicle is stolen;


Remote diagnosis and refresh: most of these vehicles are not supported temporarily and will be developed slowly in the future;



   



T-box generally refers to the intelligent vehicle terminal in the vehicle networking system, which directly communicates with the vehicle can bus to obtain the body status and vehicle condition information, and uploads these parameters to the TSP background. It can also receive the instructions issued by the background and return the execution results. Based on this, the remote control function can be extended to mobile phone app, smart key, etc.


Of course, it is also possible to connect various entertainment systems with external audio and video. T-box can be integrated with OBD module. I think it can replace OBD equipment as a rear installation. However, with the working principle and form of T-box and safety considerations, the front installation will be better.


When it comes to front loading, it's natural to mention the popular OBD five or six years ago(On Board Diagnostics)Application.



Common OBD circuit diagram




OBD box is a rear mounted product. An additional small box is inserted into the on-board baiobd port to realize networking with the cloud and read a small amount of vehicle information. Generally, there is little vehicle control, let alone other functions of Tbox. OBD refers to the OBD equipment that can be connected to the vehicle OBD diagnosis interface. It can collect vehicle bus data, carry out fault diagnosis, integrate GPS chip, acceleration sensor, etc., obtain driving data, and can play a certain security role in combination with mobile app. Of course, some other on-board equipment will also choose to occupy the OBD interface, For example, vehicle navigation HUD, etc. Since the CAN bus commonly used in the vehicle is used for communication with the vehicle, it is also called} can box in some applications, which are all rear mounted supporting products.




Installation of OBD vehicle intelligent terminal hardware



The following is the market situation of OBD in 2017-2018:

Because a certain number of vehicles running on the market before did not have networking function, we temporarily made this product for UBI insurance fleet management and other services. This is a transitional product. After the popularity of T-box in the future, its value will be very small.

T-box can be integrated with OBD module. I think it can replace OBD equipment as a rear installation. However, with the working principle and form of T-box and safety considerations, the front installation will be better. Generally, it refers to the intelligent vehicle terminal in the vehicle networking system, which directly communicates with the vehicle can bus to obtain the body status and vehicle condition information, and uploads these parameters to the TSP background. It can also receive the instructions issued by the background and return the execution results. Based on this, the remote control function can be extended to mobile phone app, smart key, etc. Of course, it is also possible to connect various entertainment systems with external audio and video.


According to the degree of cracking the original agreement, the above two on-board terminals can realize remote control window lifting, whistle, ignition, air conditioning and other operations, and even more advanced functions. Due to the need to adapt to different brands, models and models, the coverage of remote control functions is relatively limited.


Interaction between Tbox and can bus

Due to the maturity and reliability of CAN bus technology, at present, the in vehicle bus network of basically all vehicles is can. The following figure is the bus network of general vehicles.




Here is only a schematic diagram showing the general logical connection mode. The bus architectures of each company are different, but they basically include high-speed and low-speed can networks (low-speed tends to be eliminated). Most is mainly used in entertainment systems that require a large amount of data, which is not the standard configuration of all vehicles.


Tbox can not realize the control of some vehicle functions without the operation of CAN bus. There are generally three methods in the industry. OBD is not the practice of a complete vehicle factory with integrity, which is not mentioned in this answer.


1. Select direct access to can and take Tbox as a node. (this is not specifically mentioned in the column)

If you only need to realize the control function of a certain can in Tbox (generally body can, because it has network management function, the implementation is relatively simple), you can directly add Tbox to this network as a node, and use the same can transceiver to calculate and process mobile network signals, Bluetooth, WiFi and other signals into can signals. Of course, the advantage is simple and direct. You only need to do a good job in the sleep wake-up mechanism and secure access of Tbox nodes, and the network management policies of other nodes do not need to be modified. The disadvantage is that the function is limited (of course, the Tbox signal can also be forwarded to the power can through the gateway, which is troublesome, so there is method 2).


2. Integrate Tbox function with gateway

For can interaction at different rates, the gateway needs to forward signals. If Tbox function is integrated in the gateway, direct interaction with all can networks can be realized, similar to the figure below. This connection mode only needs to add network management to the nodes supporting Tbox function in the power can. The advantage is that the information transmission is direct and effective, and the implementation is simple. The disadvantage is that the security requirements are relatively high.




3. Tbox is connected to the network outside can

It is integrated in the most (or other) non can network responsible for the entertainment system and relies on the gateway to forward messages. This structure is not widely used in the industry. Its advantages: the external network is highly integrated with the entertainment system, which is convenient to realize the entertainment and social attributes of the Internet of vehicles; The information needs to be forwarded through the most gateway with high security. Disadvantages: the cost of most bus is high, and the development of most gateway is difficult.


The interaction principle is actually very simple, that is, Tbox can connect to the can network and send can messages, and the corresponding controlled node can be awakened and receive Tbox can messages without others. The implementation function is roughly the same. I hope to give more consideration to things in terms of reliability and security. In fact, with the development of automotive electronics, can bus has more and more limitations, and the industry has been slowly looking for alternatives.


FlexRay (can FD) and Ethernet are slowly emerging with corresponding standards and devices. If Ethernet is used in the car, it is basically the rhythm of flying for Tbox.


Summary:Through comparison, it is found that the control principles of OBD box and Tbox are basically similar. At present, the main "battlefield" of OBD box is the afterloading market, which is developed and sold to car owners led by auto parts suppliers, with less participation of vehicle manufacturers. Due to the analysis and cracking of relevant protocols and the certification of relevant encryption algorithms, there are few functions that can be realized, Mainly passive monitoring function; The main "battlefield" of Tbox is the front loading market, which is usually developed by the vehicle manufacturer. It can better combine with various controllers of the vehicle and realize the remote control of on-board equipment. Tbox usually completes the assembly before vehicle sales.




Common on-board Tbox


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