Designed And Implementation Of The LED Printer Data Processor Based On Embedded Linux

With the rapid development of computer technology, the printer has been widely used, printer's print speed, print quality and USB printing function is needed by user. The application of LED technology to the printer, so that it have characteristics of high reliability, higher print speed, good imaging effect, small size, energy conservation and environmental protection and so on.In this paper, in order to improve printer performance, we research embedded Linux operating system in the LED printer as data processor to complete the data analysis, image processing, print control functions. The innovation of this paper is data processor combined print controller system's other modules not only complete the basic print functions, it can also print PDF, TIF, JPEG, BMP images directly from a removable storage devices.Linux operating system as a data processor for embedded software systems. Porting Linux operating system's main work include build development environment, cutting the kernels and building the root file system. Set up the development environment includes the host installation and cross-compilation toolchain installation. Cut kernels include adding a USB printer driver and coding and adding a GPMC-driver and so on. Building root file system included modifying the configuration file and adding cross-compiled applications and so on.Data processor runs three processes associated with print control: the printer daemon process, USB printing process, and the printer status display process. The printer daemon process is running in the background as a daemon in Linux. The printer daemon and the printer status display process start on startup, daemon first initialization environment, each boot needs to be initialized only once. After the initialization, the printer daemon enters a loop to wait for the upcoming guardian data connections, receive and analyze the data and set up print parameters and other operations. A cycle including setting multiple IO, parsing PCL files, send data, and environmental clean-up operations when printing is finished. Printer status display process displays the printer's status, and when U disk inserted into the printer, display U disk file directory, the user can offline to select a file and set the print parameters to print the corresponding file.U disk printing process does not start by default, when a user insert U disk, choose a print file, printer daemon process start USB printing process. USB printing printing process main work include image processing, halftones, compression, add PCL control commands and other operations, and then sends the print data to the printer daemon process. To do the image process in data process need transplant the image processing library Mupdf. Mupdf is a C language library, it has facilitate transplant, small size, fast, and fully functional features. Mupdf can process PDF, JPEG, TIF and BMP file. In addition, the data processor needs to combine FPGA modules and halftone compression module and asynchronous FIFO and other resources to bitmap halftone and compression.The LED printer of the embedded image processor is tested by the host or U disk of the safe printing driven operating system. It is proved that the embedded image processor has the functions of data analysis, image analysis, printing control and so on.