Research On PCB Coordinate Positioning Method And The System Design

The paper accomplishes positioning PCB by two schemes. The first oneutilizes image processing technology, through OV7620image sensor which has itsown FIFO module collecting320*240pixel16bits of data, use STM32to read theFIFO data, i.e. image data. Then, process the image to get a black and white image.Scan the columns and rows to determine the position of the black spot and convertit into coordinate values.Second schemes is to utilize STC12C5A60S2chip to generate a PWM wave,through6inverters74HC04to increase the driving force of this PWM wave. ThePWM wave is applied to the PCB board by a pen, and a small voltage waveform ofPWM can be detected by a bridge circuit which will be amplified40000timesthrough two stage amplifier circuit made by AD620instrumentation amplifier. Bysuch method, it can be intuitive to observe the voltage variation. Then, put a switchchip DG201between the two stage amplifier circuit to convert PWM wave into DCsignal, and utilize RC low-pass filter to diminish the self-excited oscillation signalsproduced by amplifiers. Finally, use the10-bit ADC function of MCU to recognizethe amplified voltage, and fit algorithm of voltage to obtain the coordinate whichwill be displayed on the LCD12864screen.