2.4 maXTouch® Capacitive Touchscreen Controller

The module's touch screen interface is based on the Microchip maXTouch mXT336UD Touch Controller and operates on the touch sensor at connector J2. The touch controller scans the touch sensor and signals the host with an active-low interrupt signal (MXT_IRQ on J1) when new touch data is available.

Data communication with the maXTouch controller is performed via the I2C interface (LCD_I²C_DATA and LCD_I²C_CLK on J1). The I2C address of the touch controller is fixed at 0x4A, and is not configurable.

Note: The maXTouch has no pull-up resistors featured on the I²C Bus (LCD_I²C_DATA and LCD_I²C_CLK) or its Interrupt Line (MXT_IRQ). They must be featured on the host board driving the display.

Details of the maXTouch communication protocol are beyond the scope of this document. This module is pre-loaded with a configuration already optimized for the maXTouch touch sensor and panel, hence the developer will only focus on interfacing with the device. When developing the maXTouch controller interface during evaluation and host development, care should be taken to avoid changing the maXTouch configuration or committing changes to non-volatile storage on the maXTouch controller. To start with host interface development, users need to leverage the existing code available from Linux which is available at www.microchip.com/linux for more details or from MPLAB® Harmony, which is available at www.microchip.com/mplab/mplab-harmony.

For additional information regarding maXTouch devices, refer to www.microchip.com.