CEU Camera Usage Instructions

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Introduction

This example demonstrates how to use the CEU (Camera Engine Unit) interface on the Titan Board to connect an OV5640 camera, and display the captured images on an RGB565 LCD screen via the RT-Thread LCD framework.

Key functionalities include:

• Initialize the CEU camera interface to capture real-time video streams

• Configure OV5640 camera parameters (resolution, frame rate, output format)

• Display captured images using the RT-Thread LCD driver

• Support image format conversion (YUV422 → RGB565)

RA8 Series CEU (Camera Engine Unit) Features

The RA8 series MCU integrates a CEU hardware module for efficient capture of camera image data, supporting multiple image formats and resolutions, and enabling direct transfer to memory or display interfaces.

1. CEU Hardware Interface Features

1. Interface Types

   • DVP (Digital Video Port) interface for connecting CMOS cameras

   • Supports 8/10/12-bit data bus

   • Synchronization signals:

     • PCLK: Pixel clock

     • HSYNC: Line synchronization

     • VSYNC: Frame synchronization

2. Input Resolution and Frame Rate

   • Supports VGA, QVGA, SXGA, UXGA, and other common resolutions

   • Frame rates from 1–60 fps, configurable for different applications

3. Camera Compatibility

   • Compatible with common CMOS cameras such as OV5640, OV7670

   • Supports auto-initialization and register configuration

2. Image Formats and Processing Capabilities

1. Supported Image Formats

   • YUV422 (commonly used for video transfer)

   • RGB565 (suitable for LCD display)

   • RAW10/RAW12 (for image processing and algorithm development)

2. Image Processing Features

   • Color space conversion: YUV ↔ RGB

   • Image cropping: capture only a specific ROI (Region of Interest)

   • Image scaling: support proportional scaling up or down

   • Mirror and flip: horizontal or vertical mirroring

3. Hardware Acceleration

   • CEU contains a hardware processing unit to reduce CPU load

   • Provides fast image format conversion and scaling

3. DMA Support and Buffer Mechanism

1. High-Speed DMA Transfer

   • Works with MCU DMAC for fast memory writes

   • Supports direct writing to frame buffer or LCD buffer

2. Multi-Buffer Mechanism

   • Supports double buffering or ring buffers for continuous video capture

   • Reduces frame loss and display latency

3. Flexible DMA Configuration

   • Configurable buffer start address and size

   • Supports interrupt triggering and callbacks

4. Interrupt Mechanism

1. Interrupt Types

   • Frame End Interrupt: triggered when each frame capture completes

   • Line End Interrupt (optional): triggered at the end of each line capture

   • Error Interrupt: including buffer overflow or sync signal anomalies

2. Interrupt Features

   • Supports RT-Thread ISR callback registration

   • Can work with DMA for real-time processing and display

5. Timing and Synchronization Features

1. Line/Frame Synchronization

   • HSYNC aligns each line of data

   • VSYNC aligns each frame

2. Pixel Clock

   • CEU supports external PCLK or internal clock division

   • Ensures synchronization with camera output to avoid sampling errors

3. Data Alignment

   • Supports byte or pixel alignment

   • Automatically adjusts according to image format

6. Performance and Optimization

1. High Throughput

   • DMA + double buffering enables continuous video capture

   • Low CPU usage suitable for real-time applications

2. Reliability

   • Sync signal anomalies trigger interrupts

   • Buffer overflow detection

   • Automatic recovery from frame loss

3. Flexibility

   • Supports multiple resolutions and format switching

   • Configurable cropping and scaling regions to improve display efficiency

7. Application Scenarios

• Real-time video display on LCD

• Video capture and image processing algorithm testing

• Embedded vision applications, e.g., surveillance, gesture recognition, robotics vision

RA8 Series MCU GLCDC (Graphics LCD Controller) Features

The RA8 series MCU (e.g., RA8P1) integrates a GLCDC hardware module for driving TFT/LCD displays, enabling high-speed graphics rendering and video display, supporting multiple resolutions, color formats, and display modes.

1. Hardware Features

1. Resolution Support

   • Can drive common resolutions from QVGA (320×240) to WQVGA/XGA

   • Limited by on-chip RAM and display interface bandwidth

2. Color Support

   • Supports 1/4/8/16/24/32-bit color depth

   • Common formats: RGB565, RGB888

   • Supports palette mode (CLUT)

   • Hardware color conversion available

3. Interface Types

   • Parallel RGB (TFT LCD interface)

   • Supports 16/18/24-bit data bus

   • Direct connection to external LCD panels

   • Programmable timing: HSYNC, VSYNC, DE, PCLK, RGB output

2. Layers and Display Modes

1. Layer Support

   • Single-layer mode (single screen display)

   • Multi-layer mode (palette or hardware alpha blending)

   • Supports transparent/semi-transparent overlay

2. Display Modes

   • RGB mode (direct color output)

   • CLUT/Palette mode (indexed color via lookup table)

   • Configurable scan direction (horizontal/vertical)

3. DMA and Frame Buffer

1. Frame Buffer Access

   • GLCDC can directly access on-chip or external SRAM frame buffer

   • Supports single or double buffering

   • Supports ring buffer for continuous refresh

2. DMA Support

   • Works with MCU DMAC to reduce CPU usage

   • Can transfer images directly from memory to LCD

   • Supports line, block, or full-frame transfer

4. Hardware Graphics Functions

1. Window Cropping and Scaling

   • Can specify display window area

   • Supports simple horizontal/vertical scaling

2. Hardware Graphics Acceleration

   • Rectangle fill, color replacement

   • Image transparency processing

   • Can be combined with CEU or DMA for video display

3. Color Format Conversion

   • YCbCr → RGB

   • RGB888 → RGB565

   • Hardware accelerated to reduce CPU load

5. Interrupt Mechanism

1. Interrupt Types

   • Frame End

   • Line End (optional)

   • Access error/overflow

2. Interrupt Application

   • Integrates with RT-Thread ISR

   • Can trigger buffer update or double-buffer swap on frame completion

   • Enables smooth animations and video display

6. Performance Optimization

1. Double Buffer Mechanism

   • Reduces flicker

   • CPU can render next frame in background

   • GLCDC hardware automatically switches display buffer

2. Frame Rate Control

   • Programmable clock and line/frame synchronization

   • Supports common refresh rates (30fps, 60fps)

3. CPU Offload

   • Many graphics operations performed in hardware

   • DMA + GLCDC combination enables efficient image display

Hardware Description

The CEU camera interface and RGB LCD interface are shown in the following figure:

FSP Configuration

HyperRAM Configuration

• Create a r_ospi_b stack:

• Configure the r_ospi_b stack:

• HyperRAM pin configuration:

• The drive capability of all pins related to HyperRAM should be configured as H, and OM_1_SIO0 to OM_1_SIO7 need to be configured as Input pull-up.

CEU Configuration

• Create a r_ceu stack：

• Configure CEU：

• Configure CEU pins：

CEU Clock Configuration

• Create a r_gpt stack：

• Configure the camera clock PWM output:

D/AVE 2D Configuration

• Create a r_drw stack:

RGB LCD Configuration

• Create a r_glcdc stack：

• Configure interrupt callback and graph layer 1:

• Configure the output parameters, CLUT, TCON, and Dithering:

• Configure GLCDC pins:

LCD Backlight Configuration

• Create a r_gpt stack:

• Configure back light PWM output:

RT-Thread Settings Configuration

• Enable CUE camera, using i2c1 and ov5640 camera. Enable RGB565 LCD, using pwm7 output 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 resetting the Titan Board, the terminal will output the following message:

Here is the image displayed on the LCD screen: