1 Introduction Today, with the rapid development of electronic technology and its widespread use in automobiles, the degree of electronic electronics is increasing. The large number of electronic controls and the increased communication complexity in the automotive electronic system will inevitably lead to large and complicated wiring of the whole vehicle, shortage of installation space, reduced operational reliability, and increased difficulty in fault maintenance. In order to improve signal utilization, data information communication and resource sharing are required. The traditional electrical system peer-to-peer communication method is far from meeting this demand. On the basis of the above problems, on the basis of mature computer networks and modern control technologies, automotive network technology emerged as the times require. Through the bus, various electronic devices and devices on the car are connected into a network to realize information sharing between the devices, which not only reduces the wiring harness, but also better controls and coordinates various systems of the automobile to optimize the performance of the automobile. 2 system hardware design The hardware system designed by the hardware system has the functions of data processing, data storage, data communication, parameter setting and display, which can well capture the speed of the sensor, the temperature of the car, the running state of the engine, the water temperature and The data such as the amount of oil is transmitted, processed, stored, and displayed on the display screen to enable the driver to know the overall running condition of the vehicle body in time. The system is mainly divided into processor module, USB interface module, storage module, UART asynchronous serial port module, CAN module, 10/100M Ethernet interface module, display module and power supply. The overall structure of the system is shown in Figure 2.1.
2.1 Processor Module This system adopts a 32-bit RISC microprocessor S3C2410 developed by Samsung. It contains an ARM920T core. The chip integrates 16KB instruction cache, 16KB data cache, MMU, external memory controller, NANDFlash controller. 1 LCD controller, SDRAM controller, 3 channels, two independent UARTs, 4 channels of DMA, 8 channels of 10-bit ADC, touch screen interface, IIC bus interface, 1 USB host interface, 1 USB device interface 117-bit general purpose I/O port and 24-bit external interrupt source. The S3C2410x supports booting from NAND Flash. The system uses a combination of NAND Flash and SDRAM to achieve a very high price/performance ratio.
2.2 USB Interface Module The USB of the S3C2410 supports the USB1.1 version, which is suspended and wake-up. The USB device controller provides a high-performance, full-rate rate function control solution using the DMA interface, allowing for bulk transfers, interrupt transfers, and control transfers. The S3C2410 expands USB very conveniently. It can be connected according to the USB1.1 standard protocol, and can support both low-speed and high-speed transmission of USB.
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2.3 UART serial port module
UART refers to the asynchronous serial port. Two UART0 and UART1 are included in the ARM9 microcontroller. UART0 only provides TXD and RXD signal pins, and UART1 adds a modulation modulo MODEM interface. The rest are identical.
2.4 CAN Module This system uses the MCP2510, a stand-alone CAN controller manufactured by Philips for automotive environments and general industrial system environments. The MCP2510 supports CAN2.0B and has some new features. It is widely used and is a typical stand-alone CAN controller. The SJA1000 has two modes of operation, the basic CAN mode and the Peli CAN mode with many extended functions.
2.5 display module
Since the system selects the chip and integrates the LCD controller, just select the appropriate LCD display. The system selects SHARP's LQ080V3DG01 display. LQ080V3DG01 is a TFT-LCD display module consisting of color TFT-LCD template, drive circuit, control circuit, power supply circuit and backlight unit. The display resolution is RGB640×480, with 3.3V and 5V power supply modes. 3 Driver Design The software of the vehicle network system consists of three parts: real-time operating system, hardware driver and running on the operating system, 10/100M Ethernet USB storage device, USB mouse, USB keyboard, GPRS/CDMA, GPS. application. The real-time operating system uses the Linux operating system that is open source. The hardware drivers are mainly USB device drivers, CAN controller drivers, serial port drivers, and LCD controller drivers.
3.1 USB device driver design Linux's USB kernel subsystem provides several core data structures directly related to device driver development, defined in the kernel source code.
Static struct usb_device_id usb_demo_ids[ ] ={{USB DEVICE(venderid ,productid) } }/ * Information used to identify the device * / struct usb_demo_dev{struct usb_device usbdev ; / *points to the corresponding specific USB device*/ struct urb usbdev_irq ; / * URB * / } for interrupt endpoint processing;
Static struct file_operations usb_demo_fops = { / * device file operation function set */ owner :THIS_MODULE read :usb_demo_read ; / * read data function from device * / write :usb_demo_ write; / * write data function to device * / ioctl :usb_demo_ioctl ;/ * Control device status function * / open :usb_demo_open; / * Open device function * / release :usb_demo_release ; / * Release device function * /
}; static struct usb_driver usb_demo_driver = {probe : probe_demo ; / * device initialization function * / disconnect : disconnect_demo ; / * device unload function * / fops : usb_demo_fops ; / * device file operation function set * / static int init usb_demo_init (void) {usb_regester (&usb_demo_driver) ; / * Register a USB device* /
} The above is the framework of a typical USB device driver in Linux. It usually includes device initialization, device unloading, device opening, device release, and reading, writing, and controlling devices. It is a relatively fixed format.
3.2 CAN controller driver design Linux driver has a specific specification and some necessary modules. The init_module module is used to load the device in the driver. It is called when the system is initialized. Here arm9200_mcp2510_init() is used as the entry function of the CAN bus driver. It will mainly initialize the MCP2510, call the register_chrdev() function to register the character device driver with the system, and use the request_irq() function to process the CAN bus interrupt handler. According to the requirements of transmitting CAN data, the following data structure is designed to store one frame of data and manage the receive buffer: Typedef struct{ unsigned int id; / * The identifier of the node in the CAN network * / unsigned char data[8] ; / * The data to be transmitted, up to 8 bytes * / unsigned char dlc; / * The length of the data sent * / int IsExt; / * Determine whether the message is an extended frame * / }candata; Typedef struct{ Candata MCP2510_Candata[ 128]; / * Define a receive buffer * /
Int nCanRevpos; / * Data pointer to the location pointer of the buffer * / int nCanReadpos; / * Data read position pointer * / int loopbackmode; wait_queue_head_t wq; spinlock_t lock; }MCP2510_DEV;
The data structure file_operations is an important data structure in the driver through which the kernel accesses the driver. The application reads and writes data and controls the operation of the character device by calling the corresponding program in the _read(), _write(), _ioctl() function.
3.3 Serial port driver design The serial port driver adopts the query mode, which mainly includes serial port initialization function, data receiving function and data sending function. The serial port initialization function USIinit() is mainly used to set the parameters of the USART work. The user application can perform various processing on the received function by calling the data receiving function RevUSData(). The USART data reception and transmission is an active process, so the design of this function is relatively simple. The data send function SendUSData() is similar to the data receive function and can be called by the user program.
3.4 LCD controller driver design In the process of driving LCD design, the first thing to configure LCD controller, and the most important thing when configuring LCD controller is
Specify the frame buffer (FrameBuffer). The device file corresponding to the frame buffer device is /dev/fb*, and the data structure is as follows: Static struct file_operations fb_fops={ ower:THIS_MODULE, read:fb_read, write:fb_write, ioctl:fb_ioctl, mmap:fb_mmap, open:fb_open,
}
The function operates on the specific hardware, sets the register, and maps the display buffer. The initialization function first initializes the LCD controller. In Linux, the continuous LCD display buffer can be dynamically allocated using the kmalloc() function. The next step is to initialize a fb_info structure, add member variables, call register_framebuffer(& fb_info), and register fb_info into the kernel. Member function of structure fb_info: struct fb_ops{
Int (*fb_get_fix)(struct fb_fix_screeninfo *fix, int con, struct fb_info *info); int (*fb_get_var)(struct fb_var_screeninfo *var, int con, struct fb_info *info); int (*fb_set_var)(struct fb_var_screeninfo *var , int con, struct fb_info *info);
}
4 Conclusion This article details the design of the underlying hardware and drivers of the embedded vehicle network system and successfully completed the debugging of hardware and software. The author of this paper innovates: This network system greatly reduces the number of electronic control devices, saves the valuable space resources of the car occupied by the thick wire harness, and realizes the data sharing, communication and processing between the electronic instruments inside the car, thereby improving the safety of the car. performance.
Zhejiang Synmot Electrical Technology Co., Ltd , https://www.synmot-electrical.com