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Introduction to automobile Tbox

Release date:2021-12-28Author source:KinghelmViews:539

Telematics box, referred to as automobile T-box for short.

The Internet of vehicles system consists of four parts: host, automobile T-box, mobile app and background system. The host is mainly used for audio-visual entertainment and vehicle information display; Automobile T-box is mainly used for interconnection and communication with background system / mobile app to realize vehicle information display and control of background system / mobile app.

Principle of automobile Tbox

The vehicle T-box communicates with the host through CAN bus to realize the transmission of instructions and information, so as to obtain information including vehicle status, key status and transmission control instructions; Through audio connection, both sides share microphone and speaker output. Indirect communication (two-way) with the mobile app is in the form of data link through the background system. The communication between T-box and background system also includes two forms: voice and short message. Short message is mainly used to realize one key navigation and remote control functions.

Automobile T-box can deeply read automobile can bus data and private protocol. T-box terminal collects automobile bus data and reverse control of private protocol through OBD module and MCU; T-box can also locate the vehicle position through the GPS module, and use the network module to transfer the data to the ECS through the network. The car owner can obtain vehicle condition report, driving report, fuel consumption statistics, fault reminder, violation query, location track, driving behavior, security and anti-theft, reservation service, remote car search and other information from the cloud server through the network on the mobile app side. He can also interact with the network module indirectly through the connection with the server through the network on the mobile app side, Then, through the channel between the network module and MCU, MCU is finally used to provide services such as controlling car doors, windows, lights, locks, horns, double flashing, reflector folding, skylight, monitoring central control warning and airbag status.

Some functions of automobile Tbox

1. Remote control users can control the door switch, whistle and flash, turn on the air conditioner, start the engine, vehicle positioning and other functions through the mobile app. By using these functions, the use of the vehicle is not only convenient, but also saves users a lot of time. For example, in summer and winter, turn on the air conditioner for cooling or heating a few minutes before getting on the bus, so that users don't have to wait. When getting on the bus, the temperature in the car will drop or rise to a comfortable temperature, so that users can really experience "warm in winter and cool in summer when entering the car"; The owner can also use the remote start function to warm up the vehicle in winter, and can use the remote shutdown engine when the vehicle is stolen; If the owner forgets the key in the car, or is not sure whether to lock the door but is far away from the vehicle, he can remotely control the unlocking and locking through the mobile app; In addition, you don't have to be afraid to find a car in a large parking lot. You just need to use your mobile phone to check the vehicle's positioning through app to understand the general orientation, and then control the vehicle's whistle and flashing light to know the specific location of the vehicle.

2. Remote query can realize remote query of vehicle status through mobile phone app, such as whether there is oil in the vehicle's fuel tank, whether the windows and doors are firmly closed, how much battery power is left, how long it can drive, etc. very comprehensive vehicle status information can be seen on the mobile phone without having to check it in person, If there is a problem, the user can also use the mobile phone to query it at a glance; At the same time, the mobile app can also self diagnose the vehicle condition to see if there is a problem in each system. If there is a problem in a system, the app end will alarm and remind. In this way, if it is a long-distance user, you don't need to check one by one, and you can directly query the vehicle condition with the mobile app.

3. The security service function is mainly designed for driving safety and anti-theft, including roadside rescue assistance, emergency rescue help, automatic vehicle change alarm, remote automatic upload of vehicle abnormal information and other services. These functions are of great significance and can even save lives at critical moments. For example, the collision automatic rescue function. After the vehicle collision triggers the airbag, the T-box will automatically trigger the passenger car customer rescue hotline number, automatically upload the vehicle location information to the background, and the background will send information to all emergency contacts. The SMS contains the accident location information and event information, so that the accident vehicles and personnel can be rescued in time.

Communication between Tbox and can

The following figure shows the mainstream bus architecture in the current vehicle (each box in the figure represents an ECU)

OBD: On-Board Diagnostic 

MOST: Media Oriented System Transport 

In order to facilitate management and control, can bus is generally divided according to functional requirements. Traditional vehicles are mainly divided into power and body. Body bus adopts low speed and power adopts high speed. There is also a special can for diagnosis, which is connected to the OBD interface in the vehicle. In addition, due to the great demand for in vehicle navigation, video and audio, the CAN bus can not provide such a high transmission rate of video data. Therefore, in the on-board navigation and entertainment system, the most bus with a rate of 22.5mb/s or other similar high-speed buses are generally used. The communication between different bus networks all depends on the gateway to forward messages. Therefore, the gateway is basically the most important part of the in vehicle bus, and its importance is equivalent to the spine of the human body. The architecture of each manufacturer will be slightly different according to its needs, but it is this model on the whole.

If the vehicle network is to be realized, that is, the vehicle and the network are linked. Today, when can bus is dominant, modules with networking function are bound to be added to the CAN bus architecture in the vehicle. Among the vehicle networking products that have realized the first stage technology, there are probably three technical solutions.

1. OBD box networking

Insert the networked equipment (OBD box) into the OBD diagnostic interface of the vehicle, and read the relevant driving information of the vehicle through the diagnostic can. This scheme is adopted by many Internet enterprises, and only a few automobile manufacturers adopt it.

Advantages: no need to change the bus architecture in the motor car, no need for the cooperation of automobile manufacturers, plug and play. Because the OBD port is mandatory for vehicles, it is mainly used for vehicle detection and later program upgrade and maintenance.

Disadvantages: generally, it can only read the data in the vehicle, can not realize remote control, and the function is limited. Moreover, as long as the car factory seals off the diagnostic can communication when the car is running, this method is useless.

2. Telematics (wireless communication on-board system) is directly connected to can bus

The module with remote communication function is directly connected to the CAN bus, the information of each ECU is read through the telematics module, and the corresponding control information is sent to realize some remote control functions.

Advantages: the message does not need to be forwarded by the gateway, the information transmission is direct and effective, and the implementation is more convenient.

Disadvantages: insufficient security. Once telematics is attacked, the CAN bus of the whole vehicle is almost exposed to hackers. I suspect that this is the way Cherokee was used before.

3. Telematics is connected to the network outside can

As shown in the example in the figure, the telematics module is added to the most bus, directly connected with the entertainment system, and forwards the corresponding vehicle information and control information through the most gateway.

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.


Although these three technical schemes have their own advantages and disadvantages, as long as they are connected to the CAN bus, they can basically realize the access and control of each ECU in the vehicle, whether it is the body part or the power part, if allowed by the gateway. Then why should I put controlling the body and controlling the power in two different stages? This is mainly due to the safety problem. From a technical point of view, there are basically no obstacles through remote starting the engine and control steering, but many manufacturers rarely do so today. Everyone is afraid of this safety.

When the intelligent assisted driving system is immature, opening the power part to the Internet of vehicles has no obvious advantages and selling points. At this stage, consumers will not pay more because you can start remotely. However, if the intelligent assisted driving technology becomes more and more mature, and even automatic driving occurs, there is no reason for the power part not to be released, and the corresponding safety problems will also be paid attention to by the industry. As for the intelligent assisted driving system, when will it mature? It seems that you can't get around the bottleneck of CAN bus.

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