Interface circuit between STM32 and four-wire resistive touch screen

As shown in the figure below, the STM32F103F103 is directly connected to the four-wire resistive touch screen through its own I/O port to implement the touch screen controller function. Among them, PA8, PA9, PA10, and PA11 are used as the control terminals of four triodes respectively. By controlling the on and off of the triodes, the Y+, Y-, X+, and X- of the four-wire touch screen are controlled. PA1 and PA2 are two A/D conversion channels. , connecting Y+ and X+ respectively for calculating the X and Y coordinates of the touch point. The internal interrupt of the PA3 connection is used to detect whether there is a touch action on the touch screen. When the touch screen is running normally, let PA8, PA9 and PA11 output 0 and PA10=1, that is, only let VT2 be turned on. When there is a touch action, D1 is turned on to give an interrupt signal to PA3. After receiving the interrupt request, STM32F103 immediately sets PA8=1 and turns on VT1, so that voltage is added in the Y+ and Y- directions and the A/D conversion is started at the same time. Channel PA2, calculate the Y coordinate of the touch point by inputting the X+ upper voltage, and then similarly set PA8 and PA10 to 0, PA9, PA11 as 1, start the A/D conversion channel PA1, and calculate the touch point X by inputting the Y+ upper voltage. coordinate of.