Flexible platform for networking automotive electronic systems

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Flexible platform for networking automotive electronic systems [Copy link]

Since cars need to face a variety of different road surfaces and driving conditions, the electronic systems in the car must adopt a variety of different network standards to meet different performance requirements. In order to better meet the requirements of different network standards, the interconnection network of the in-vehicle electronic system has been developing towards the network-in-network model. The network-in-network model basically uses the telematics control unit (TCU) as hardware, which is the hardware interface connecting all the communication networks of the in-vehicle electronic system. As for software, the application layer of the transmission control protocol/Internet protocol (TCP/IP) can be regarded as a universal software that connects different communication networks in the car, allowing us to control all electronic devices in the car through the network. As long as the application software uses the transmission control protocol/Internet protocol as a universal interface, it can fully operate and communicate with the application programs on other nodes.

　　This article mainly introduces the layered software structure of the network-in-network design, and describes how the network-in-network uses its layered software to support the electronic devices of the new generation of cars, including automotive electronic system control (powertrain, speed gear, air conditioning/heating system, etc.), audio and video entertainment system, mobile phone and Internet access system to meet the requirements of the next generation of drivers.

Layered communication protocols

　　A layered structure can improve the flexibility and scalability of communication protocols. A functional layer can store data about its specific implementation to prevent higher-level functions from obtaining this data, ensuring that these higher-level functions are not affected by the execution of other functions. For example, a file transfer protocol may not even know whether to use fiber, wired or wireless technology to transmit the data. As long as all data link protocols use the same protocol, higher-level protocols can use any protocol instead.

　　Figure 1 shows that layered communication protocols can simplify software design by providing programmers with a high-level application programming interface (API). If a programmer wants to transfer a file, a high-level file transfer protocol can provide a simple set of services for the programmer, allowing the programmer to list the file server name, source file name, destination file name, etc.

　　From the perspective of the application software programmer, the API can be seen as a highly simplified user interface that can independently handle all the troublesome issues related to data communication without being affected by other functional layers. The API is an ideal virtual connection that allows programmers to ignore details such as parity errors and flow control. Programmers only need to provide the necessary information to establish a connection.

　　When data communication reaches a certain level, we must provide a physical connection for the transmitted data, but the functional layer between the API and the physical layer can handle all the low-level operations to support this virtual connection.

　　This model is divided into four layers:

　　● Application layer: Provides protocols that can be used directly by application software, including File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Hypertext Transfer Protocol (HTTP), etc.

　　● Transport layer: Transmission Control Protocol (TCP) uses a bidirectional end-to-end connection to transmit TCP information segments. User Datagram Protocol (UDP) uses a message transmission model to send and receive UDP datagrams.

　　● Network layer: Responsible for transmitting and receiving information packets through the network. Most network layers use the Internet Protocol (IP) to transmit information packets called IP datagrams.

　　● Physical layer: This is the interface to the data link hardware. The protocol stack has different functional layers, and this layer is actually responsible for loading and retrieving data into and out of the registers and storage buffers of the communication peripherals. Networks such as Controller Area Network (CAN) and Ethernet use the common cable network connection standard. Bluetooth radio frequency networks called piconet are popular wireless communication networks used by wireless headsets, mobile phone hands-free remote control systems and other short-range audio/data communication systems. Wireless infrared communication systems generally use the IrDA standard.

　　Each functional layer does not need to know the operation mode of the upper and lower layers. In fact, each functional layer must not be affected by these operation modes in order to interoperate with other services in different functional layers. For example, the network layer is only responsible for transmitting information packets from the source to the destination. It does not know and does not need to care whether these information packets are transmitted using a one-way UDP datagram communication method or a two-way TCP connection.

　　Layered protocols have greater scalability because all links must adopt a modular structure and standard interfaces according to the protocol. If someone invents a new data link technology and wants to run the entire stack of the protocol in the new media, then he only needs to write a compatible physical layer driver. All other functional layers do not need to be changed, so the replacement and update of technology becomes very simple and easy.

Network-within-a-network model

　　Because different situations have different requirements, the next generation of cars will need to have multiple different communication networks for their electronic systems to ensure that their stability and bandwidth can meet the requirements of different situations. We can solve the problem of communication between different networks by using layered protocols and a central gateway processor.

　　The following are the in-car communication networks that may be installed in the next generation of cars:

　　● Controller Area Network: This medium-frequency band network has highly reliable characteristics and is a standard network that almost all cars must have

　　. ● Bluetooth Piconet: This is a medium-frequency band wireless communication network designed for mobile phones and laptops. It is also a standard network that almost all cars must have.

　　● Audio-visual network: This is a high-frequency band network designed for playing audio and video. There are many different applicable protocols on the market, including Domestic Data Bus (D2B), FireWire (IEEE 1394), Media Oriented Systems Transport (MOST) and Mobile Media Link (MML).

　　● Low-cost wired network: This is a network that uses universal asynchronous receivers and transmitters, and is also equipped with interfaces such as I2C, SPI and MicroWire, so that different chips can obtain direct bus connections. Therefore, it is the most suitable low-cost interface for keypads, displays and sensors.

　　● Low-cost wireless network: This is a low-frequency band wireless network using ZigBee or other dedicated networks. It can provide low-cost wireless connections for tire pressure sensors, RF remote control keys for alarms and door locks, and other electronic systems.

　　The future generation of in-vehicle electronic system interconnection networks will generally use a variety of different controller area networks. These controller area networks are mainly divided into high-speed and low-speed. Low-speed networks with speeds as low as 10kbps~125kbps can provide connections for different control devices. For example, the starter can control the movement angle of the rearview mirror through the network, and the taillight group can use these networks to shorten the interconnection line. In addition, high-speed controller area networks with speeds as high as 126kbps~1Mbps can support important functions with higher performance requirements such as powertrain control.

How to network automotive electronic systems

　　Figure 2 shows a wireless remote interface system that allows users to access the automotive electronic system interconnection network for diagnostics, where the telematics control unit can be manufactured using very cost-effective chips.