RGB LCD Example Guide

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Introduction

This example demonstrates how to use the GLCDC module of the RA8 series MCU together with RT-Thread’s LCD driver framework on the Titan Board to drive an RGB LCD screen, enabling image display and interface updates. This document provides a detailed overview of RA8 GLCDC peripheral features and the RT-Thread LCD driver framework, along with example configurations and usage methods.

RA8 Series GLCDC Module

1. Overview

The GLCDC (Graphics LCD Controller) is a high-performance graphics controller integrated in RA8 series MCUs, specifically designed to drive TFT/RGB LCD screens. It supports various resolutions, color formats, and graphics processing functions. Combined with RT-Thread’s LCD driver framework, it provides a unified interface for screen initialization, refresh, graphics rendering, and DMA-accelerated operations.

The RA8 GLCDC enables image output from either internal MCU memory or external frame buffers to RGB/LCD displays. Key features include:

• Frame buffer control: Supports multiple frame buffers for page switching or double-buffered display

• Color format support: RGB565, RGB888, ARGB8888, etc.

• Graphics processing: Background layers, text/graphics composition, alpha blending, palette mapping

• Synchronization signal generation: HSYNC, VSYNC, DE (Data Enable)

• DMA support: High-speed data transfer, reducing CPU load

• Interrupt functionality: Frame-end and line-end interrupts

2. Module Architecture

The RA8 GLCDC module mainly consists of the following submodules:

1. Layer Composition Unit

   • Supports multiple layer stacking

   • Provides alpha blending, transparency control, and color keying

   • Allows rotation and flipping of layers

2. Frame Buffer Interface

   • Supports access to MCU internal SRAM or external memory

   • Provides single or double buffering to ensure continuous display

   • Works with DMA to automatically read image data

3. DMA Controller

   • Automatically transfers pixel data to the RGB output port

   • Configurable burst length to improve bandwidth utilization

   • Supports circular transfer, suitable for video or animation scenarios

4. Timing Generator

   • Automatically generates HSYNC, VSYNC, and DE signals

   • Supports TTL interface RGB timing

   • Polarity, sync width, and front/back porch timings are configurable

5. Interrupt and Event Controller

   • Provides frame-end and line-end interrupts

   • Can be used for page switching, dynamic drawing, or scrolling display

   • Supports interrupts triggered by DMA transfer completion

3. GLCDC Working Principle

1. Frame buffer read

   • GLCDC uses DMA to fetch image data from memory, supporting single or double buffering for continuous display.

2. Layer composition

   • Supports multiple layers such as background + foreground + icons/text

   • Provides alpha blending and palette mapping

3. Pixel timing output

   • Generates HSYNC/VSYNC/DE signals according to LCD interface requirements

   • Supports RGB parallel interface, TTL interface, or LVDS (depending on board implementation)

4. Interrupts and events

   • Frame-end interrupt (VBlank): Can be used to update the next frame

   • Line-end interrupt: Useful for scrolling displays or dynamic rendering

4. GLCDC Supported Features

Feature Category	Description
Resolution	Up to 800×480 (depending on MCU model and clock)
Color formats	RGB565, RGB888, ARGB8888, etc.
Multi-layer	Background + foreground + icon layers, supports blending
Frame buffer	Single/double buffer mode, DMA improves performance
Palette	8/16-bit palette mapping for color conversion
Sync signals	HSYNC, VSYNC, DE, configurable polarity and timing
DMA support	Automatic memory transfer, CPU-free
Interrupts	Frame-end, line-end interrupts for synchronized refresh
Rotation/Flip	Supports 90°/180°/270° rotation and X/Y flipping

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RT-Thread LCD Driver Framework

RT-Thread provides a LCD driver framework, which abstracts the underlying controller and supports different screen types and MCU peripherals. Key interfaces include:

Main Interfaces

Function/Macro	Purpose
rt_device_find("lcd")	Find the LCD device handle
rt_device_open(dev, flags)	Open the device and initialize the LCD hardware
rt_device_control(dev, cmd, args)	Control the LCD, e.g., update image, set backlight, read screen info
rt_device_write(dev, pos, buffer, size)	Write pixel data to the LCD
rt_device_read(dev, pos, buffer, size)	Read pixel data from the LCD (supported on some screens)
rt_device_close(dev)	Close the LCD device

Hardware Description

FSP Configuration

HyperRAM Configuration

• Create a r_ospi_b stack：

• Configuration r_ospi_b stack：

• Configuration HyperRAM pins：

RGB LCD Configuration

• Create a r_glcdc stack:

• Configure interrupt callback and graph layer 1:

• Configure Output、CLUT、TCON and Dithering:

• Configure GLCDC pins:

LCD Backlight Configuration

• Create a r_gpt stack:

• Configure back light PWM output:

D/AVE 2D Configuration

• Create a r_drw stack:

RT-Thread Settings Configuration

• Enable RGB565 LCD in RT-Thread Settings, using pwm7 output screen backlight.

Compilation & Download

• RT-Thread Studio: In RT-Thread Studio’s package manager, download the Titan Board resource package, create a new project, and compile it.

After compilation, connect the development board’s USB-DBG interface to the PC and download the firmware to the development board.

Run Effect

After reset the development board, type lcd_test command in the terminal to run the brush program.