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A bleeder circuit of copper plate resistance is used to design a drawing board,in which the AD conversion module is based on AD7982,the master control module is based on the STM32F103,and the liquid crystal display module is based on LCD12864.By searching the linear data sheet which records the change of copper plate resistance-voltage,the drawing board can display the coordinates and quadrant of the contact,the text and the track of the pen on the LCD screen when the pen touches on the 15 cm×10 cm copper plate.This design is an ideal solution because of its high precision and low power consumption.

Ideal AD conversion should be a straight zero-crossing line in the Cartesian coordinate axis system. While in practical engineering, the signal processing circuit, chip performance and other factors have an impact on the accuracy of conversion. Therefore a linear fitting method is adopted to improve the conversion accuracy. An automatic modification of AD conversion based on Ethernet is presented by using software and hardware. Just by tapping the mouse, all the AD converter channel linearity correction can be automatically completed, and the error, SNR and ENOB (effective number of bits) are calculated. Then the coefficients of linear modification are loaded into the onboard AD converter card's EEPROM. Compared with traditional methods, this method is more convenient, accurate and efficient，and has a broad application prospects.

STM32F1 series processors are based on ST's new generation of ARM cortex-M3 processor core to meet the industrial control，medical，consumer and other areas of application requirements． At the same time，ST companies also launched a set of DSP function library for the STM32F10x series，enabling common digital signal processing． In this paper，a set of FIRfilter design and implementation is proposed for the STM32F10x series． Experiments show that the integer filter coefficients can replace the float coefficients in FIRfilter design． When the sampling rate is 256 samples per second，the FIRfilter is of the order of 128 and takes only 1．5ms to finish filtering 256 samples，fully meeting the design requirements for industrial control systems．