A touchscreen controller is a device that detects positional contact pressure on a visual display surface. A hand-held stylus or one or more fingers are the typical implements used as pointing devices. Controllers interface data between a processing system and the touchscreen element associated with the display, usually in an SPI or I2C serial format. Products that utilize touchscreen controllers include cellphones, touchscreen monitors, portable instruments, and tablets.

Controllers are optimized for low power as they are typically being used in portable battery oriented applications. Most controllers support a wide range of operating voltages to be compatible with as many logic interfaces as possible.  They have internal temperature measurement and voltage references to improve measurement accuracy. Because they attach to devices that could be the victim of a spark discharge, they typically have higher than normal electrostatic discharge protection.

A touchscreen can be implemented in a number of ways. They can be resistive arrays where pressure on a position of the screen causes two layers overlaid on the screen to electrically short. By scanning rows and columns, the position of the short can be detected. There are five common types of touchscreen technology available—5-wire resistive, surface capacitive, projected capacitive, surface wave acoustic (SAW) and infrared. Leading edge controllers support concurrent detection by two methods like mutual capacitance and self-capacitance to obtain a good compromise between technologies for accuracy and sensitivity.

Controllers have different technologies based upon the different touchscreen types. Invariably a voltage is applied across a row and column array arrangement that makes up the touchscreen. For a resistive style panel the voltage is direct current (DC), for capacitive this is an alternating current (AC). The array is scanned by testing rows and columns while they are being stimulated.  Testing involves detecting the impedance of the circuit by the amplitude of the voltage across the array at each coordinate. This is achieved by a differential amplifier and an analog to digital converter (usually of the successive approximation type). This information is passed to the processor for analysis.

Touchscreen controllers can also have a pen stylus interrupt input. This enables a low power mode by only scanning the touchscreen when the stylus is being used.

There is usually a driver provided by the manufacturer to facilitate development, and there may be a calibration process required to align the display with the touchscreen coordinates.