Design and Application of Reconfigurable System Based on Programmable Logic Device

The requirements for each bus are different. Low cost and relatively low rate buses are required in low-end applications, and high-speed real-time transmission is required for visual media in high-end applications. Because it is difficult to determine which standard will eventually win, many automotive OEMs support multiple standards. For designers, these uncertainties will prolong the development cycle and may eventually lead to the loss of business opportunities.

The reconfigurable system based on FPGA introduced in this paper can be reprogrammed in the late design stage or even mass production stage to adapt to the changes of standards and protocols. The bus interface can be verified in advance in the form of configuring IP core, which can save time and energy, so it can shorten the market time of the product.

Figure 1: on board network system and its rate

On board infotainment system and mobile information equipment, especially on-board navigation system, need strong operating system and interconnection. At present, several organizations and alliances lead the standardization direction of automobile bus, including most collaboration alliance, IDB forum, Bluetooth SIG and so on (Figure 1).

Multimedia oriented system transmission (most)

The most network, promoted by the most collaboration alliance, is used to connect multiple devices in the car, including car navigation system, digital radio, display, cellular phone and DVD. Most technology has been optimized to use plastic optical fiber, support data transmission rate up to 24.8mbps, have high reliability and scalability in the equipment layer, and fully support real-time audio and compressed video. Most bus has been recognized by BMW, DaimlerChrysler, Harman Becker, oasis silicon systems and other companies. A notable recent example of most projects is Harman

Becker automotive systems applies it to the latest BMW 7 series.

Intelligent transmission system data bus (IDB)

IDB forum introduces idb-c, idb-1394 and standard IDB interfaces for OEM companies engaged in developing after-sales market and portable devices. Idb-c based on CAN bus can be applied to equipment with data rate of 250kbps. The application of idb-c includes establishing interconnection between digital consumer devices such as digital telephone, PDA and audio system.

Idb-1394 (based on IEEE-1394 FireWire) is designed for high-speed multimedia applications, in which a large amount of information needs to be transmitted quickly. Idb-1394 is a network with a transmission rate of 400m baud rate using optical fiber technology. Applications include DVD and CD changers, displays, audio and video systems. Idb-1394 also allows 1394 portable consumer electronic devices to interconnect and work together with an on-board network. Zayante is a current supplier of 1394 physical layer devices for the consumer market. The company uses Ford Motor Company for IEEE1394 demonstration. The demonstration included plug and play interconnection of a digital video camera, a Sony Playstation II game console with two monitors and a DVD player.

Digital data bus (D2B) communication network

Digital data bus (D2B) is a network protocol, which is used for multimedia data communication integrating digital audio, video and other synchronous and asynchronous signals with high data rate. Its data transmission rate can reach up to 11.2mbps. The data bus can be established either along unshielded twisted pair, called "smart line", or through a single optical fiber. This communication network is promoted by British C & C company and has been adopted by Jaguar, Mercedes Benz and other companies. For example, the integrated multimedia communication system has been used in Jaguar x, s and new XJ sedan models.

D2B optical fiber is automatically configured at startup, which can be adapted no matter what equipment is online at that time. This means that new devices can be easily connected to the network during their lifetime. Automobile manufacturers using D2B optical fiber multimedia system can find that the technology involved in this standard is what they have known. The standard has backward compatibility, which can ensure that new products can be added to the automotive system throughout the life cycle. D2B optical fiber is based on an open architecture. When adding a new device or function to the optical fiber ring, it is only simple to expand without changing the cable wiring. The bus only uses one cable, one polymer optical fiber or one copper cable, which can be used to process multimedia data or control information in the vehicle. This can provide better reliability, reduce the number of external components and connectors, and significantly reduce the weight of the whole system.

Figure 2: a general in car multimedia design block diagram

Bluetooth

Bluetooth wireless technology is a low-cost, low-power and short-range wireless technology, which is suitable for mobile devices and WAN / LAN access points. It is a computing and wireless communication industry specification, which describes how to easily interconnect mobile phones, PDAs and computers, and use short-range wireless connections to interconnect homes with commercial phones and computers.

For example, a driver can use a Bluetooth wireless headset to communicate with a cellular phone in his pocket. As a result, the driver's attention is distracted and safety is reduced. The automotive industry has established a special interest group (SIG) to develop a Bluetooth draft for cars. Members of this sig include amic, BMW, Daimler Chrysler, Ford, GM, Toyota, VW, etc.

Advanced security system FlexRay

FlexRay is a new network communication system specifically aimed at the next generation of automotive applications or "by wire" applications. By wire applications require high-speed bus systems. These high-speed bus systems must be deterministic, fault-tolerant and can support distributed control systems. BMW, DaimlerChrysler, Philips semiconductor, Motorola (the semiconductor business is now called Freescale) and the latest member Bosch have developed and established FlexRay as the next generation application standard.

FlexRay communication system is more like a communication protocol. It contains a specially designed high-speed transceiver and defines the software and hardware between different components of FlexRay "node". FlexRay protocol defines the function and format of communication process in networked automotive system. The technology is designed to meet key automotive needs, such as reliability, practicability, flexibility and high data rate, so as to make up for the shortcomings of in vehicle communication standards such as can, Lin and most.

Due to the increasing amount of communication data of automotive electronic control components (ECU), it is very important to obtain high data rate. FlexRay initially aimed to achieve a data rate of 10Mbps, but now the protocol can also achieve a higher data rate.

Timed trigger protocol (TTP)

Timed trigger protocol is mainly used in those reliable and fault-tolerant real-time distributed systems. It ensures that there is no single failure point. TTP is a mature network solution. It is low cost and can cope with critical security applications. TTP has been adopted by many airlines because of its preciseness and obvious safety. Ttagroup is the competent organization of TTP. At present, its members include Audi, PSA, Renault, NEC, ttchip, Delphi and Visteon.

Timed trigger can (TTCAN)

The common communication in can network is event triggered. When multiple demand information is sent at the same time, there will be peak load. The non-destructive non arbitration mechanism of can can can ensure that the information is transmitted according to the marked priority. For the real-time system, the whole system must be analyzed to ensure that the deadline of all transmission and even peak load is met. In order to solve this problem, TTCAN came into being.

TTCAN is an extension of CAN protocol. It has a session layer at the top of the existing data link layer and physical layer. The protocol implements a hybrid, time triggered TDMA process. It is also suitable for event departure communication. TTCAN is expected to be used in engine management system, transmission and chassis control through wired applications.

FPGA helps designers out of design difficulties

The reconfigurable platform allows designers to change the system bus or interface in the later stage of the design process or even in mass production. The concept of reconfigurable system makes it possible to try, test and use different standards, and if you find that they do not match another bus interface already installed in the car, you can try until you find the best configuration.

Programmable device (PLD), field programmable gate array (FPGA) and complex programmable logic device (CPLD) allow designers to control all stages from prototype to pre production and mass production. ASIC or ASSP based devices do not have this flexibility and controllability. PLD can alleviate the inventory problem because this general-purpose device can be used in multiple projects, while ASIC can only be used in specific applications. After the components using programmable devices are put into use, they can even be reconfigured through the wireless communication link to upgrade the system or add additional functions.

By using the IP core module, the reconfigurable hardware platform can shorten the time to market. For example, the can core of Memec design includes a complete data link layer, including framer, transceiver control, error correction core design and flexible interface to obtain the status and frame reference of each internal system. The bit rate and sub bit segments can be reconfigured to meet the special timing requirements of the connected can bus, and the error counter and error interrupt events will report errors. The core is designed to provide a bus rate of 1Mbps, and its minimum core clock frequency is 8MHz. The can core can provide an interface between information filter, information priority mechanism and various system functions such as sensor / actuator control. In addition, it can also be embedded in system applications as an interface between microcontroller and various peripheral functions.

Without using discrete devices, only using the IP core for a part of a more complex design can provide an interface to the can or LIN bus. Reducing the number of components can bring many benefits, such as reducing the cost of the whole system, reducing inventory, improving system reliability and reducing PCB complexity and layers. As shown in Figure 2, a general in vehicle multimedia design block diagram is shown. The design uses can core, PCMCIA interface, PCL bridging, IDE interface and other functions. These functions can be modified and changed in the design stage, or modified according to the requirements of end users. Through reconfiguration of FPGA in the system, This mode can also be extended to modify or upgrade the system on site.