Research On Combined Graphics Display System In Aircraft Cockpit Based On FPGA+DSP

The design of graphics generator for driving LCD is a key technology of avionic system andrun-time generation and antialiasing of graphics are main contents of it. Foreign technology ofcombined graphics display system was researched and used on aircraft from90decade last century. Inthis field, our country once dropped behind and fast grown up in last10years. Now, products in homeare used on some aircrafts, but the technology still drops behind. In this paper, according to thecharacteristics of the combined graphics display system in aircraft cockpit, graphics generation,accelerating and anti-aliasing techniques were discussed. Furthermore, some novel design methodswere researched and advanced.Researching on the graphics generation in aircraft cockpit's combined graphics display system, anew design method for the graphics system based on FPGA and DSP was proposed and a prototypemachine was developed, according to the characteristics of the graphics. In order to improve theperformance of the system, FPGA was used as main processor to generate graphics and DSP was usedas coprocessor to count few parameters while double frame buffers were used. The system acceleratedthe graphics drawn by FPGA, and the resolution was improved. Software development waspredigested using general functions library on DSP.According to the generation of the graphics in aircraft cockpit, a new algorithm was developedfor line generating after reaching on fundamental algorithms. Canonical Bresenham algorithm canonly generate one pixel of a line each time. The new algorithm can generate pixels of a line row byrow and inherit the advantages of Bresenham algorithm without division and decimal fraction, so itsefficiency was proved to be better. Using for referent of two-step algorithm, a novel method wasproposed to gengeate two rows of a line each time. These algorithms can be realized by FPGA toincrease the speed of lines drawing.Researching on the antialiasing algorithms for line, character and circle, a new algorithm waspresent for line antialiasing using integer shift, addition and compare to find the grayscale of eachpixel, and the antialiasing speed was improved. Because the graphics in aircraft cockpit include threepixels wide lines, a new method for arbitrary wide line generation wae proposed based on the newline antialiasing algorithm. Antialiasing for circle was complex and the effect of algorithms inexistence was not satisfactory. To improve efficiency and effect, an integral algorithm was present forcircle anti-aliasing based on midpoint generating algorithm. The new algorithm found the grayscale ofeach pixel according to the distance between the center of a pixel and the circle. The algorithm abandoned the high-order epsilon and corrected the error by simple calculation. A method was built todraw a circle with64levels of grayscale by forecasting the grayscale change between neighbouringpixels using integer shift, addition and compare without floating-point and division. The algorithm forcharacter antialiasing was also researched. The new algorithms were convenient to realize onhardware. The algorithms proved to be efficiently and effective.A project was present based on FPGA for horizontal Indicator in Aircraft Cockpit. Graphics weregenerated, memory and LCD were controled by FPGA according to the positions of words and linescounted by DSP. Less calculation and time were needed by utilizing the symmetry of graphics,parallel counting and old graphics regenerating. The project was proved to be better and faster withsimply bus.Attitude Indicator in Aircraft Cockpit spends much time on generating graphics and a newalgorithm based on FPGA was present. The algorithm got the coordinate of a scanning beam point ofthe horizon and used level line to fill. The horizon and profile were counted while filling. Lesscalculation was needed before filling to generate the graphics with less memory accessing, so thegraphics of attitude Indicator were generated faster.