The Design And Implementation Of U Disk Read-Write System Based On TI 5409 DSPs

Along with the popularization and development of USB (Universal Serial Bus), people have higher demands on USB. People hope that USB can be used in more extensive computer field, and slip the leash of PC. Now, development of USB host system based on embedded processor becomes leading edges of USB technology. Under such a background, author designed and developed the U disk read-write system based on TI TMS320VC5409 DSP processor and CH375 USB host/slave chip, and the core of the system is the USB host system.Now, most USB host systems based on embedded processor generally make use of ARM or singlechip system, and they hardly use DSP processor. If they used the DSP processor, the type usually was TI 2000. This U disk read-write system which is designed and developed in this article makes use of TI TMS320VC54X DSP processor.In addition, this U disk read-write system has much higher utility value, such as: it can realize mass storage for DSP system; it can realize software upgrade or data updating for DSP system; it can realize data exchange between DSP system and PC; we can grasp the method on developing driver of USB device; we can also make use of it as a USB device development system.In this article, first is the research about the theory and technology of embedded DSP processor system development and USB protocol. Then, on the basis of theory research and much experimental results, this article gives the scheme of USB host system which is based on TI TMS320VC5409 DSP processor and CH375 chip. Then, this article introduces the hardware platform and software system. Finally, this article realized the U disk read-write system.This USB host system uses TMS320VC5409 DSP processor, and the processor is the action initiator of the reading and writing; uses CH375 chip as the host controller of USB host system, and uses it to realize the USB protocol; uses the USB connector to realize the connection between the USB host and the USB device; the U disk is the USB mass storage device, and is the target which the system want to read and write. After the theory research and the design scheme work, it is the building of the hardware platform and the design of the software system, the process of the design and realization is with the following main steps: (1) First is the comprehensive planning of the hardware platform of the U disk read-write system. This system includes eight modules, such as: power module,DSP processor module,CPLD logical control module,bus driver module,USB host control module,U disk,keyboard control module and LCD display module, and the DSP processor module and the USB host control module are the core of the system and consist of the USB host control system.(2) The system uses TMS320VC5409 DSP chip,CH375 chip,LCD12864 screen,Lattice2128CPLD chip,HD7279 chip,singlechip-90C32,74LVC16245chip and TPS767D318 chip to design the hardware circuit of the system. On the basis of holding the design and development method of these chips, it uses the PCB design software called"Protel Dxp"to design the circuit principle drawing and PCB drawing. After making sure that the drawings have no error, it is the time to make the PCB board. After the PCB board is completed, the following work is jointing the board and testing. So far, the hardware platform of the U disk read-write system is completed.(3) This step is to design the software of the system. First, it needs to analyze the control mechanism and using method of the CH375 USB host control chip, then, it needs to analyze the layered structure of the U disk read-write software. The software has four layers, such as: I/O operation function layer,firmware function layer,interrupt service routine and file system function layer,main program layer.(4) Design and realize three I/O operation functions, such as: void CH375_WR_CMD_PORT (unsigned int cmd),void CH375_WR_DAT_PORT(unsigned int DAT) and unsigned int CH375_RD_PORT( ).On the basis of realization of the I/O operation functions, combining the handling mechanism of the USB protocol in the CH375 chip, it realizes 14 firmware functions, such as: mode choice of CH375 function,chip testing function,state configuration function,standard communication commands,USB device storage operation functions and so on. It also realizes the interrupt service routine, the function of the interrupt service routine includes four aspects, such as: first, the program gets the interrupt state from the CH375 chip, clears up the request of the chip and makes the INT# pin come back to high level; second, based on the interrupt state, it makes sure the state of the U disk; third, it reads the data from the input buffer of the CH375's host point to the DSP processor; fourth, it writes data from the DSP processor to the output buffer of the CH375's host point.(5) In this step, it designs and realizes the read-write software, which makes the U disk as memories and designs and realizes the system software, which realizes the file system. When it makes the U disk as memories, the read-write method is very like flash, it's easy and fast. If you make the U disk as memories, the PC can't read or write the data from the U disk directly, after you write data to the U disk, because the PC observe file system, so the PC needs particular tools to read the data. Under the mode of file system, DSP processor needs to analyze the file system in the U disk, and reads or writes it following the rules of the file system. This read-write course is complex and slow, usually, it needs hundreds of sentences. After the data is written into the U disk using file system, PC can find the files and read them.The U disk read-write system can support hot inserting and pulling out, can identify and configurate the U disk automaticly, can read or write data steadily to the U disk based on sector and can read or write the files in the U disk. The software using file system realizes such operation: file-enumeration,file-building,file-open,file-reading/writing,file-locating,file-close,file-delete,file-location and so on.Today, development of USB host system based on PC and USB expansion for computer peripheral are quite mature and development of USB host system based on embedded system is very hot, in the future the technology of OTG, which can realize the directly communication between two USB devices, will be the research direction. Along with the development and maturation of USB technology, the ability of USB will get stronger, it will drive the development of the area of IT, and take convenience to people.