Resistive touch screen solution analysis
I. Basic principle of resistive touch screen
Resistive touch screen consists of two transparent conductive layers (ITO/metal grid) and insulating spacer points, and touch positioning is achieved through pressure sensing:
Structural layer:
Outer layer (touch layer): flexible PET film, with conductive layer coated on the inside.
Inner layer (base layer): hard glass or PET, with conductive layer coated on the outside.
The two conductive layers are separated by micron-level insulating points (such as polyester particles), and do not touch each other when not touched.
Working mechanism:
When touching, the outer conductive layer is compressed and deformed, and contacts the inner conductive layer to form a voltage divider circuit.
The coordinates of the touch point are calculated by measuring the voltage changes in the X and Y axis directions (need to cooperate with the driver chip to complete AD conversion and coordinate solution).
II. Core components and classification
Core components
Touch screen body: supports single-point touch, and some models simulate "pseudo-multi-point" through algorithms (such as two-point scaling requires specific driver support).
Driver chip: Common models such as XPT2046 (SPI interface, supports 4-wire resistive screen) and ADS7843 (parallel interface), responsible for collecting voltage signals and outputting coordinate data.
Flexible circuit board (FPC): connects the touch screen and the main control chip to transmit electrical signals (4-wire or 5-wire solution).
