Design Of Auto Integrated Control Central Unit Based On CAN-Bus

With the rapid development of embedded technology and automotive electronics technology and with the raising development of interaction of car information, how to apply embedded systems and related technologies to the transport vehicles which are closely related to people's daily travel, and let the drivers easily and comfortably driving their own car have become an important research topic of automotive electronics. Auto Integrated control unit is an R & D projects relying on it.There are various ways in achieving control of automobile. The car in the early has a lot of wiring between the control units and the units which are been controlled. When these units continuously increase, car will become"heavy up". It not only increases the number of wiring, but also be harmful to the car's maintenance and fault detection. In order to solve this problem, automotive field-bus came into been. It let electronic units mount on the bus and let them use the specific protocol to communicate. And the CAN-Bus is the most suitable choice of field-bus. CAN-Bus has superior performance, high stability and low price. Therefore,this design chose CAN-Bus as the communication protocol between auto integrated control central unit and other units.Auto Integrated Control Central unit is the export of control information. We often need to open the headlights while driving, adjusting air conditioning,seats,windows, listen to the radio and all of this can be control by the auto control center unit. Integrated control central unit package these message, packaged it as CAN's signals of communication and transmit it to the corresponding function module of electronic control unit, this unit then use these signals to drive motor sports, or control repeater actions to complete the control process.Base on the function of integrated unit of automotive, construct the system's hardware and software architecture. According to the design requirements, implementation difficulty and laboratory conditions select program as follow: Microprocessor LPC2294 plus Operation SystemμC/OS-Ⅱplus CAN-Bus.Then begin the design of the issues: mainly include hardware design, operating systems design, software design and Debugging process.In the hardware design of auto integrated system, we chose LPC2294 which is based on ARM architecture of 32-bit as core processor, and add power module, clock module, external memory module, LCD module, test module, control module. The whole hardware circuit is the organic integration of the various parts in which LPC2294 is main part. Because the LPC2294 has integrated four CAN controllers, it's not need to add CAN controller in the hardware design, such as SJA1000 CAN controller. What we only need to do is connecting four CAN transceivers, such as 82C250 CAN transceiver. Power module mainly achieves the regulator output, filter ripple interference. Stable and reliable power is the base for the normal operation of the circuit. Control module mainly includes buttons and knob potentiometer, they belong to the input control device while achieve people's control of car. LCD module mainly achieves the function of human-computer interaction, let people more easily, more intuitively control the car.In the selection of the operating system, we use the real-time operating systemμC/OS-Ⅱ. Base on the type of microprocessor, we transplantμC/OS-Ⅱto our system. It needs to re-edit or write INCLUDES.H, OS_CPU.H, OS_CPU_C.C, OS_CPU_A.ASM. After completion we need to test if the code is success transplanting to the board. We can write a small LED-button control board to test the migration problem. After the success of the transplant, we need to know the kernel of the operating principle and task management mechanisms:HowμC/OS-Ⅱinitialize the stack, howμC/OS-Ⅱswitch task, howμC/OS-Ⅱorganize a mission design and so on.μC/OS-Ⅱusually transfer news through the semaphore, event flag groups, message mailboxes and message queues in the task of the multi-task system. It makes it possible of interaction between tasks that the system uses the flag and message.In program design,using multi-task design, dividing the task to CAN-BUS task, key processing tasks, A/D processing tasks, LCD display task. In the CAN programming, according to CAN register map address, initialize the CAN registers. Set the interrupt handling in the process. Generally we only deal with receive interrupt, data overflow interrupt and bus error interrupt which is important or serious, and neglect of other interrupt.In the process of hardware debugging, first check the power of solder circuit board. Ensure that no power on error. And then check the function of ISP and JATG.In the process of software debugging, first write the underlying functions and drivers. Then write the test modules as independent as possible, analysis the corresponding program of the underlying function and driving. Discover the problem, modify the program according to debug phenomenon and save the file after modify the correct. After correcting the bottom functional and the drive, add them to the project file and write the whole program. The associated scheme can be made base on the requirements of other ECU.