Implementation Of USB Host Controller At Printing Interface Of Intelligent Apparatus

During the design of intelligent apparatus,the data processing is completed by single chip frequently. In the single chip system, most frequently used print device is minitype printer such as TP and UP series and so on. They all adopt parallel interface. However recent years, with the USB interface becoming the standard interface of PC, low-grade printer's interface had also been transplanted into USB interface from parallel interface. At present, universal printer has international standard interfaces and the size of paper is optional and its price is more cheaper than minitype printer. So more and more single chip systems start to adopt universal printers.In the universal printer, often used interface includes parallel interface, serial interface and new-style interface USB. Although Parallel interface has fast transfer speed, the credible transfer distance is too short and interference will increase with the increase of transfer distance. The transfer distance of serial interface is long enough, but its transfer speed is too slow. USB interface has both fast transfer speed and long enough transfer distance, besides, it also has many other advantages such as plug and play, low power consumption and low price and so on. So currently,most printers have adopted USB interface. Now the companies which produce printers with USB interface include Epson, HP and so on. They all have their own print control languages. As to the choosing of printers with USB interface, considering from performance and price, the ink jet printer which is made by HP corporation has more advantages. Moreover the print control language PCL is open to customers, so it is more convenient for developers to control printers with PCL.The microcontroller used for this project's main control module can be selected from DSP, ARM and singlechip of 51 series, but DSP or ARM will make the circuit more complicated and make the volume of PCB more bigger, they are not suitable for the development of portable interface which needs small volume. While singlechip will make the design of circuit more simple and volume of PCB more smaller, it's very suitable for the development of portable interface. Considering from performance and price, singlechip is not only good in performance, but also cheaper than DSP, ARM in price. Moreover, the condition of lab is finite, so the 51 series singlechip, W78E54, had been adopted. The companies which produce USB Host controller include Philips, Cypress. The chip of Philips such as ISP1161, ISP1362 and Cypress such as SL811HST all have the function of USB Host, but SL811HST needs less data lines. Because of finite data lines and address lines in singlechip, moreover ISP1161 and ISP1362 will make data lines deficient, it's better to adopt SL811HST. At aspect of hardware's design, it had been successful to produce a circuit board with SL811HST and W78E54. At aspect of software's design, it had been successful to design the C language codes of USB protocol and flow chart through the thorough study of USB protocol. The codes of print control had been developed through study of print control language PCL and process of print. The function of this circuit board is to realize controlling the printer with USB interface as a host without PC and changing the data format into the one that printer can accept. The debugging of the whole system had been completed with emluator and its matched software Medwin. The application of this technology will reduce the product cost to great extent and make the customers to use printers more conveniently.