Electronic Competition 2013 Question G: Handwriting Drawing Tablet

The purpose of this design is to make a more accurate handwriting drawing board. It is initially planned to use MSP432 or STM32 for control. A constant current source is connected to the copper-clad board and eight precision resistors are introduced. When the touch pen touches any position on the copper-clad board, it will A small voltage signal is detected, and the differential signal is collected through the movement of the test leads. The differential signal is helpful for signal transmission. We will follow the voltage of the collected signal to improve the load capacity of the circuit to obtain a relatively stable small voltage signal, and then proceed to the previous step. After setting up a high-precision and high-gain amplifier and passing through the low-pass filter circuit, it enters the voltage follower circuit to obtain a more stable and accurate signal. Finally, the signal data is obtained through the AD chip collection and processing by the microcontroller and the processed signal is displayed on the LCD screen to achieve the design requirements.