Recently, many customers have reported that the vehicle remote data terminal cannot directly collect vehicle can data through the OBD interface. In fact, this principle is simple, but the actual operation is more complex. Today, I’ll comb it for you, get familiar with the gateway, bypass the gateway to collect data, or collect data directly on the gateway.

1、 Where is the gateway?

We know that it takes a door to go from one room to another. On the car, these brainy engineers use this simple entrance and exit to the car: sending information from one network to another needs to go through a “gateway”, some may be more than one, including “Jiayuguan, Tongguan and pingyangguan”. The gateway of the on-board network is getaway.

As the core control device of the automotive network system, the gateway is responsible for coordinating the protocol conversion, data exchange and fault diagnosis between CAN bus networks and other data networks with different structures and characteristics.

Gateway is a device used to provide network compatible functions such as protocol conversion and data exchange when collecting networks with different architectures or protocols for interworking. It can also be popularly called the connector between networks, protocol converter and data translator. The gateway can be used for both wide area interconnection and local area interconnection. It acts as a computer system or equipment for conversion, and does translation between two systems using different protocols, data or languages, or even two systems with completely different architectures.

Before, there was a concept of a bridge, such as can to RS232, which is similar to a bridge. The gateway repackages the received information (such as DBC) to meet the needs of the target system. At the same time, the gateway also provides filtering and security, so we can’t read any data on the OBD interface. For example, Volkswagen models can only collect the voltage of one OBD, Tesla obtains a VIN code (for licensing), which is filtered out by the gateway data filtering function.

2、 Role of gateway

For the time being, professionals should not spray in the following aspects:

1. The gateway converts the data on the LAN into identifiable ackii codes, such as OBD2 diagnostic data, to facilitate diagnosis.

2. Coordinate the data information sharing of low rate information and high rate information in automotive network system.

3. Be responsible for receiving and forwarding information.

4. Activate the operation of a control unit or a local area network.

5. Realize the synchronization of internal data of vehicle network system.

6. Translation.

The gateway will connect different types of bus systems, such as can information, can diagnosis, can drive, instrument, comfort, etc. there are great differences. Engine can is generally high-speed, diagnosis and comfort can is low-speed, multimedia, etc. some adopt Ethernet, most and other bus systems, so the gateway must ensure the normal progress of these data exchanges, Ensure that the data buses with different rates can work together through the gateway.

Suruide cracked the gateway system of BMW in 2014, mainly studying DCan, kcan and ptcan. Kcan (body can bus) with transmission rate of 100kbit / S is equivalent to the speed of subway, which is mainly used when the body control function is realized; Ptcan (powertrain can bus) with transmission rate of 500kbit / S is equivalent to the speed of green train; The airbag system bus (byte flight) with a transmission rate of 10mbit / S is equivalent to the speed of the motor car; The audio-visual entertainment system bus (most) with a transmission rate of 22.5mbit/s is equivalent to the speed of high-speed rail. Although the data transmission rate and data flow of each bus system are different and vary greatly, under the overall arrangement and intelligent dispatching of security and gateway module (equivalent to Shenzhen station), it takes charge of bus, taxi, subway, high-speed rail and xiaolvpi, running smoothly Work together.

After the output data of different bus systems arrive at the gateway, the gateway needs to do further processing, filter the speed, data volume and urgency of each information in the gateway, buffer and store it when necessary, and do fault monitoring and diagnosis at the same time, which is busier than the village women’s director.

3、 Working principle of gateway

As just mentioned, it is most appropriate to use the process of passenger conversion in the railway station to illustrate the working principle of the gateway. At a certain station, platform 1 arrives at a EMU (driving can bus with data transmission rate of 500kbit / s), there are hundreds of passengers (data) on the train, and there is a express train (body BCM information can bus with data transmission rate of 100kbit / s) at platform 2, While waiting, some passengers have to change to this express train, and some passengers have to transfer to the express train to continue their travel. Of course, there are many times when passengers get down from this train to the waiting hall to wait for the corresponding train number, which is equivalent to the buffer function of gateway information.

This transfer function of the station, that is, the function of allowing passengers to change trains so as to reach their respective purposes through vehicles with different speeds, is the same as the gateway function of driving can bus and comfort information can bus. The main task of the gateway is to enable normal information exchange between two systems with different data transmission rates.

4、 Where are the gateways installed?

First of all, in BMW, the central gateway module, security and gateway module, multi audio system controller, convenient access starting system, control display, combination instrument, body gateway and other control units all have gateway functions. In Audi and Volkswagen, depending on different models, the gateway may be installed in the combination instrument, in the on-board power supply control unit, an independent gateway control unit or on-board remote intelligent gateway.

Since all the information through the CAN bus is used by the gateway, the gateway is also used as the diagnostic interface. The old Volkswagen and Audi query the diagnostic information through the K line. Now they basically use the diagnostic can to complete this work.

The data bus diagnosis interface (Gateway) of Audi A8 inherits the well-known functions. It is connected with can comfort, can drive, can expansion, can display and operation, can diagnosis, FlexRay bus, most bus and LIN bus system. It is generally installed in the electric control box on the right side of the luggage compartment. The connected bus circuit mainly functions:

1. Control unit networking gateway

2. Most bus ring diagnostic control unit

3. Battery monitoring device control unit

4. Generator

5. Voltage regulator

The data bus gateway of Audi A7 is installed in the middle position under the rear seat;

BMW data bus gateway is installed under the carpet in the bent foot state of the main driving position;

The gateway of Porsche is under the driver’s seat, and the wireless intelligent gateway is in front of the glove box of the co driver;

Volkswagen is generally above the accelerator pedal in the center console.

Tesla Model3 is above the side of the front passenger’s right foot trim panel.

Conclusion: the project can not be done, but it can’t damage the car

Then we know that there are different rates of interaction information in the gateway and various on-board communication systems. While understanding and operating, we also want to remind you that the remote intelligent terminals of the Internet of vehicles, especially the projects with automobile control, complex can data interaction, automobile whole vehicle control strategy and can message translation, should not be forced, Don’t make a pile of fault codes for a good car. Consult xiaxuruide first.

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