Multi-function Stimulator Evoked Potential Based On FPGA

EPs (Evoked potentials) are, by definition, a potential changes which is producedby a specific stimulus to the particular part of the nervous system in the cerebral cortex.EP is important for the diagnostis of the neural pathways functional abnormalities of thevisual, auditory, and somatosensory. EPs are, although not directly diagnosis the disease,reliable as modern imaging examination as CT, MRI in localization diagnosis. EPtechnique is strong objective and can provid a large of precise information whichgreatly expands clinical application of the nervous system.Along with the development of the computer technology and electronicinformation technology, and the application of specific integrated circuit widely used,the modern medical instrument design is more and more intelligent, miniaturized, andmulti-functional. FPGA (Field programmable gate array) is high integration, goodreliability and simply to use, the short design cycle and so on, gradually become theengineer’s first choice in designing complex digital circuit. Based on these, this paperputs forward a design and successfully designs the system that based on the FPGAmultifunctional evoked potential stimulator.The evoked potential stimulator based on FPGA multifunctional, produces thestimulus which is required by the auditory evoked potentials and somatosensory evokedpotentialsand visual evoked potentials. There are pattern stimulus and flash stimulationin visual evoked potentials, including graphical stimulus such as vertical and horizontalbar, checkerboard and ring patterns. It designs white noise, short, dense waves,rarefaction waves and other sound stimulations in the auditory evoked potentials. Thereis current stimulation in the somatosensory evoked potentials. The article separatelyintroduces the idea from the hardware design and software design. In hardware designsthere are bipolar control circuit and booster circuit in stimulating current, VGA interfacecircuit in graphical stimulus, UART interface circuit in serial communication; TLC5615D/A converter interface circuit, reset circuit, power and the configuration circuit.Software designs include VGA timing, graphics produing, pulse modulation wavegeneration, D/A converter and serial communication timing. Finally, it discusses thedesign of communication interface between computer and FPGA.The system is designed by using the CycloneⅡ FPGA, which is produced byAltera’s company, as main controller and a small amount of peripheral circuit. The new designed evoked potentials stimulation system is better than traditional one, in thesimple circuit structure, multiple functions, small volume, the stimulation outputaccurate and reliable, stable performance, convenient conversion, and wide range ofapplication, and so on. The system can also well satisfy the evoked potential detectionperformance requirements.