Main points of software design for in-vehicle infotainment system

Faced with increasingly fierce market competition and increasingly discerning users, auto manufacturers and auto parts suppliers have been working hard to innovate-products with newer technological content and better user experience are constantly being applied to automobiles. The advanced in-vehicle infotainment system has entered a new technological era. It has evolved from a simple system that originally controlled the radio or air conditioner to a complex large system that can now include hands-free phones, satellite navigation, Internet services, and front and rear seat audio and video playback that supports multiple media. Whether it is a high-end product, or a low-end product, the hardware and software design of such a system must meet strict security standards, while at the same time having good ease of use and flexibility. This article will give some thoughts on the software design of the system from the aspects of safety, real-time, environmental protection and novelty, hoping to help engineers engaged in the development of such systems.

safety

The safety mentioned here refers to (1) the system can provide effective services for a long time without failure; (2) once a failure occurs, the system can handle it; (3) the system can automatically save the fault diagnosis file.

The principles of dealing with security-related issues are isolation and redundancy. Isolation is modularity. Redundancy is to increase backup. For hardware design, modularization and adding redundant devices are very straightforward. The actual challenge comes from the security design of the software, and most system failures are due to software errors. A well-designed software module should ensure that a failure in one module will not cause other modules to fail, nor will it cause the entire system to fail; and the actual system design should also ensure that the failed module restarts quickly or is backed up in time Module replacement, while the rest of the entire system is operating normally.

For example, a task in the system fails-if you want to rewrite the memory area belonging to another task, the system's monitoring program will detect that this is an illegal event, and restart the failed task, while saving the fault diagnosis file to For developers to solve problems in the future-the monitoring program can record the system status at the time of the failure in great detail, which can help developers quickly locate the problem.

Obviously, for a large system such as an in-vehicle infotainment system, the traditional single-core operating system is difficult to achieve the above-exemplified operations because it does not adequately isolate the memory space of kernel tasks and application programs. The QNX microkernel real-time operating system, which is very popular in industry, has achieved the isolation of various system services after years of practice and innovation, and has become a good basis for designing high-security software.

real-time

Simply put, real-time performance means that system tasks get effective results within an effective time.

The in-vehicle infotainment system is a complex multi-tasking system, which contains many subsystems that interact with the automotive network, such as CAN and MOST, as well as other communication protocols, such as RS232, Ethernet, and Bluetooth. It is very important to consider the real-time characteristics of the system from the beginning of the system software design. On the one hand, the introduction of real-time design can bring users a better application experience, such as stable and smooth multimedia playback, accurate and effective navigation prompts, etc .; on the other hand, the real-time design of the system can guarantee certain mission-critical Smooth implementation, such as Bluetooth phone and reverse screen playback. Conversely, if the system cannot handle the priority and real-time performance of each task well, then during the actual operation of the system, it is inevitable that one or more tasks cannot be completed in time, resulting in system failures and user complaints. .

More critically, the entire system is so complicated, it usually takes hundreds of milliseconds from the shutdown state (power off completely) to the system startup to enter the normal operating state. When the car is started, the CAN device usually sends a signal to turn on within 65 milliseconds. The infotainment system connected to the CAN bus must be ready to receive the power-on signal within 55 milliseconds or less and respond to the power-on signal within 100 milliseconds. If the infotainment system cannot respond to the CAN start signal in time, it will most likely be considered a faulty CAN device and be excluded from the CAN network.

Starting from the real-time design, the system must start the corresponding CAN network information before completing the initialization. The traditional way is to use additional auxiliary devices to perform such tasks-increasing hardware costs. Now, using QNX's "mini-driver" technology can completely eliminate these auxiliary devices. The design of the mini-driver allows certain device drivers, such as the CAN driver, to be used during system startup—smoothly handling event responses from the CAN network; when the system startup is complete, a more complete driver will take over all mini-driver Task-the cost of software is very low.

Environmental protection

Environmental protection means that the system can effectively carry out power management.

Power management in the car is a very challenging task. Car power is a battery with limited power. After the car is turned off, on the one hand, the in-vehicle system, especially the infotainment system, must not have excessive power consumption, and it must be ensured that the normal battery can still ignite smoothly after a few days or even weeks; on the other hand, the infotainment system It also needs to be able to respond effectively and timely to specific events under ultra-low energy consumption. If there is not a multi-level standby state, the system must be completely restarted every time, then not only has a long boot time every time, but also difficult to meet the correct response to many real-time events, such as the CAN described in the previous section Turn on signal.

The solution is to customize the multi-level standby state according to specific needs, so that the infotainment system can gradually enter each low-power standby state as time goes by and the battery power decreases until it is completely shut down. In each different standby state, the system can respond to specific events and enter the working state in a sufficiently short time.

However, the traditional power management standards APM (Advanced Power Management) and ACPI (Advanced ConfiguraTIon and Power InteRFace) are difficult to apply to the power management program of in-vehicle infotainment systems. APM and ACPI are mainly used for power management of personal computers. APM is a program that runs on the BIOS (a device that is rarely used in in-vehicle infotainment systems). Computer applications or operating systems will rarely know the power management decisions made by APM, so this solution cannot provide what we need. Customizable multi-level power management status. ACPI adopts the method of determining the power management status by the operating system, which can make more complex and effective power management. However, in the in-vehicle infotainment system, the operating system often does not know the specific power status of each application, such as whether the car is turned off, whether the Bluetooth device is working, etc., and these are the key points of the in-vehicle system power management, so ACPI cannot Requirements for on-board system power management.

Based on the QNX operating system, power management can be developed as an application. In this way, system designers can design targeted power management solutions based on different system requirements. Through the communication between the application programs and the application program and the operating system, the power state of each system module can be accurately controlled, so that the energy can be used effectively and environmental protection can be promoted.

Novelty

Novelty means that the product must have a personality and be distinguished from other similar products.

For in-vehicle infotainment systems, novelty means a man-machine interface that can be quickly customized according to customer requirements and a graphic display with rich texture and rich content, whether it is a media player, a web browser, or a satellite navigation system. All of this is related to the development of graphical user interfaces. How to modularize the human-machine interface well in the design stage is a key issue that designers must consider when they start designing, otherwise it will be painful to face the new needs of customers in the future-whether to redesign the software or reject the customer's needs Not only that, if the human-machine interface cannot be well modularized, sometimes the underlying protocol changes, and redesigning the human-machine interface is an inevitable problem.

Therefore, the modularity of the human-machine interface is not just the stripping of the shell, it actually contains the choice of data expression and the definition of device operation. Since the human-machine interface part is usually a large part of the code input of the in-vehicle infotainment system, the high-quality modular human-machine interface program and related drivers can significantly reduce the cost of system expansion. On the one hand, modularity improves code reusability, on the other hand, they also reduce the investment in testing. It is hoped that design developers can fully consider this issue.

Summary of this article

This article puts forward some thoughts on the software design of in-vehicle infotainment system from four aspects of safety, real-time, environmental protection and novelty, and hopes that these ideas can bring a little boost to the booming Chinese automotive electronics.

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