Design And Implementing Of PDF417 Barcode Decoding Terminal

The technology of two-dimension barcode is more and more widely used in daily life and industry. PDF417 is a promising 2D barcode not only because it has mature technique but also because it has obvious advantages such as high capacity of information storage, wide range of coding, strong privacy and reliability in decoding. As our country's national standard, PDF417 is suitable for industry production, national defense, commerce, and communication application.In this paper PDF417 barcode standard and codec are deeply researched, based on which decoding terminal's hardware platform whose core is DSP and software architecture are expounded in detail. The key point of the paper's work is the design and implementing of PDF417 barcode'processing and decoding with high speed. The program optimizing and function expansion are also included in the paper. The result of debugging shows that the terminal can run stably with the average decoding speed over 10 times per second.The image reading module uses a laser camera specially designed for barcode reading which can scan several barcodes each time. The hardware part adopts TMS320C6713 as its core, and is associated with SDRAM to store the image; the control circuit is implemented by CPLD. The barcode image read from the image reading module is stored in SDRAM; then DSP loads the image and does pretreatments to solve the problem of variety of illuminative intensity. Based on deep research on key technology of PDF417 barcode's recognition and decoding, a fast method of barcode location is proposed to solve the problem of time-consuming and low-accuracy in locating the position of barcode. With this method barcode's position can be located precisely, and oblique image and twisty image can be straightened easily. Finally through projection the layer positions can be got and the decoding result is acquired by decoding layer by layer at the same time with the guarantee of error detection and error correction. After implementing prospective function, program optimizing is done to make full use of the hardware resource, which contributes to acquire more efficient program.The test result demonstrates that the terminal's decoding speed of both PDF417 barcode and DataMatrix barcode is over 10 times per second, which is in leading position in this field.