4.1 Display Interface and Requirements Overview

The Raspberry Pi Touch Display 2 is a 7-inch touchscreen with a 720x1280 resolution, requiring a 83.33 MHz pixel clock at 60 Hz, interfaced via a 34-pin MIPI DSI connector.

The display features an ATtiny Atmel microcontroller for power and backlight control and a Goodix GT911 touch controller that supports up to five simultaneous touch points.

Understanding the display’s initialization sequence is crucial when developing a custom display driver. Each display controller needs a specific set of initialization commands to ensure correct power up and configuration. These commands are usually provided in the display’s documentation or reference drivers. In this project, the ILITEK ILI9881C Linux driver was used as a reference to develop the custom bare-metal driver for the Raspberry Pi Touch Display 2 panel.

Note: Detailed information about the Raspberry Pi Touch Display 2, including the display’s interface specifications, pinout and controller details (ILITEK ILI9881C controller, ATtiny Atmel MCU and Goodix GT911) can be found in its Device Tree Source (DTS) overlay file in arch/arm/boot/dts/overlays/vc4-kms-dsi-ili9881-7inch-overlay.dts.

The DTS overlay file provides critical configuration data for I2C communication, display initialization sequence, display controller, touch controller and power sequence in Harmony.