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Evaluation kit kick starts FlexRay applications

Posted: 16 Jan 2006 ?? ?Print Version ?Bookmark and Share

Keywords:neelima chaurasia? fujitsu? fujitsu microelectronics america? automotive safety? automotive reliability?

As the demand for automotive safety, reliability and comfort increases, the amount of automotive electronics is also increasing, creating the need for high-speed control in power-train and by-wire systems. Automotive manufacturers require new protocols that offer higher bandwidth, flexibility andperhaps most importantdeterministic behavior. The FlexRay serial communication protocol supports such in-vehicle communication infrastructure requirements and enables high-speed control applications.

The FlexRay protocol was developed by companies such as BMW, Bosch, DaimlerChrysler, Freescale, GM, Philips and Volkswagen. Its architecture delivers communication rates of up to 10Mbps, along with the significant advantage of deterministic behavior. The protocol includes a dual-redundant channel and uses scalable static and dynamic message transmission that deliver guaranteed message latency time. In addition, a system based on FlexRay can be programmed for synchronous and asynchronous transmission that provide higher flexibility compared with the CAN protocol, which affords asynchronous transmission only. In addition, the protocol supports clock synchronization via a global time base, collision-free bus access, message-oriented addressing via identifiers and scalable system fault-tolerance using either single or dual channels.

The FlexRay frame is divided into three segments: header, payload and trailer. The header section includes the frame ID, payload length, header CRC and cycle count. The frame ID identifies a frame and is used for prioritizing event-triggered frames. The payload length contains the number of words that are transferred in the frame. The header CRC is used to detect errors during the transfer. The cycle count contains the value of a counter that advances incrementally each time a communication cycle starts. The payload section contains the data transferred by the frame. The length of the FlexRay payload or data frame is up to 127 words (254 bytes). The trailer segment consists of three 8bit CRCs to detect errors.

Designers' tasks
A major challenge for designers starting with FlexRay is to write a communication driver. FlexRay's underlying time-triggered approach requires several planning steps in the control design phase; more are required with the more familiar procedure for the CAN interface. These requirements include advanced planning for task configuration and message scheduling.

Another challenge for the designer is to test the FlexRay systems. This requires an appropriate prototyping environment. For instance, a FlexRay-based engine control system needs to simulate engine speed, process crankshaft signals and generate output signals for ignition and injection systems. This generates the need for appropriate tools and powerful prototyping systems able to handle the dynamics of the FlexRay protocol.

Many semiconductor vendors are working on FlexRay controller development and will integrate FlexRay with a 32bit MCU. To get developers started on FlexRay-based systems, Fujitsu offers an FPGA-based development evaluation kit that provides a multifunctional evaluation board for the Fujitsu 32bit flash MCU as a host controller. It includes a CPU board, FlexRay main board and daughterboard (hosted on the main board) with a Fujitsu FPGA-based FlexRay controller as a target. The daughterboard is hosted on the FlexRay main board and can be used as a standalone FlexRay controller that can be interfaced to any CPU using an external bus interface.

The kit can be used for software development and testing using the integrated Softune Workbench development environment, with monitor debugger or with the emulator system. These tools enable the designer to start FlexRay system evaluation.

To get started with the kit, designers should first be familiar with the FlexRay IP-module, the E-RAY specification and the evaluation board hardware that comes with it. By being familiar with the kit's capability the designer will be able to resolve issues such as hardware integration that can arise when hooking up the hardware while working with the kit.

After familiarization, the boards can be connected together with the appropriate sockets provided on each board. As soon as power is turned on to the FlexRay main board that also provides power to other boards, pre-program sample software on the MCU will start running and FlexRay bus activity can be observed using an oscilloscope or any FlexRay bus analyzer tool. To reprogram the MCU or to edit or debug the program, the evaluation kit requires a PC or compatible hardware with an RS-232 port. This requires downloading the Softune Workbench, which enables designers to edit, compile, build and debug the program.

Board characteristics
The CPU board's 32bit MCU has 512KB of flash ROM and 24KB RAM on-chip memory. Also, to meet the demand for the application development phase that requires larger memory, the board has 1MB of external flash that can be used for code and constant data. The external 2MB RAM on board can be helpful for external debugging using a monitor debugger.

The board features push buttons for external interrupts and a reset signal for MCUs. There is also an RS-232 driver and DB9 connector for internal on-chip UART. In addition to the general-purpose use UART, the board provides connectivity to the PC for monitor/debugger communication or for programming the on-chip flash memory. A one-channel CAN transceiver for an on-chip CAN controller is useful for developing a CAN-based system, for examplea suitable environment for gateway application development.

The kit's main board is used as a baseboard, providing a plug-in for the daughterboard with the FlexRay controller and two PHY-layer modules with FlexRay transceivers. These modules are optional components ordered separately from third-party developers. The main board carries the power supply for all secondary voltages. It provides connectivity to the host processor and both FlexRay channels via RS-485 transceivers. Each communication channel can be configured for the bit rates of up to 10Mbps.

- Neelima Chaurasia
Sr. Applications Engineer
Fujitsu Microelectronics America




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