This STM32U5 series devboard is part of the family of ultra low power ST MCUs. It has a large amount of internal memory and the embedded NeoChrom GPU which accelerates LVGL rendering. With such a large internal SRAM, direct double buffering is possible at the great speed of internal SRAM.
You can purchase a STM32U5G9J-DK2 from https://estore.st.com/en/stm32u5g9j-dk2-cpn.html
Here is a video and measurement results of the benchmark demo running in double-buffered direct mode with NeoChrom, LTDC driver with VSYNC, and no OS enabled.
| Name | Avg. CPU | Avg. FPS | Avg. time | render time | flush time |
|---|---|---|---|---|---|
| Empty screen | 24% | 29 | 5 | 5 | 0 |
| Moving wallpaper | 23% | 29 | 8 | 8 | 0 |
| Single rectangle | 3% | 28 | 0 | 0 | 0 |
| Multiple rectangles | 9% | 29 | 3 | 3 | 0 |
| Multiple RGB images | 11% | 29 | 3 | 3 | 0 |
| Multiple ARGB images | 12% | 29 | 3 | 3 | 0 |
| Rotated ARGB images | 8% | 29 | 2 | 2 | 0 |
| Multiple labels | 52% | 29 | 16 | 16 | 0 |
| Screen sized text | 93% | 19 | 46 | 38 | 8 |
| Multiple arcs | 20% | 29 | 3 | 3 | 0 |
| Containers | 23% | 29 | 5 | 5 | 0 |
| Containers with overlay | 67% | 29 | 20 | 19 | 1 |
| Containers with opa | 28% | 29 | 7 | 7 | 0 |
| Containers with opa_layer | 46% | 29 | 13 | 13 | 0 |
| Containers with scrolling | 42% | 29 | 13 | 13 | 0 |
| Widgets demo | 91% | 25 | 20 | 20 | 0 |
| All scenes avg. | 34% | 28 | 9 | 9 | 0 |
- MCU: Arm Cortex-M33 @160MHz
- RAM: 3MB internal
- Flash: 4MB internal, 128MB External
- GPU: NeoChrom (GPU2D), ChromArt (DMA2D)
- Resolution: 800x480
- Display Size: 5"
- Interface: Parallel RGB
- Color Depth: 24-bit (this project uses 16 by default)
- Technology: LCD
- DPI: 187 px/inch
- Touch Pad: Capacitive
- Arduino-compatible pin headers
- Application USB-C
- GPIO header
- Connect a USB-C cable to the USB-C port labeled STLINK USB CN8 and your PC.
- Install STM32CubeIDE.
- Clone this repository repository:
git clone --recurse-submodules https://github.com/lvgl/lv_port_stm32u5g9j-dk2.git
- In STM32CubeIDE, click File > Open Projects from File System, click Directory, choose the cloned repo, and then click Finish.
- Click the hammer icon to build the project. The "Debug" build mode is used, even though full optimization is enabled.
- Click the play icon to upload it to the board.
- Click the bug icon to start the debugger.
- Interactive debugging is available over USB-C
- For the best debugging experience, change the optimization level to
-O0instead of-O3. The program execution will be more similar to the source code. Right click the project in the Project Explorer sidebar, click Properties. Go to C/C++ Build > Settings > MCU/MPU GCC Compiler > Optimization. Choose None (-O0) Under Optimization level.
Some things were changed from the default code generation.
The two linker scripts were modified to reserve 750kb of RAM at the start of the region for a framebuffer.
/* Memories definition */
MEMORY
{
FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 4096K
RAM2 (xrw) : ORIGIN = 0x20000000, LENGTH = 750K
RAM (xrw) : ORIGIN = 0x200bb800, LENGTH = 2258K
}
RAM2 is not referenced anywhere. Instead, Core/Src/lvgl_port.c hardcodes the memory address 0x20000000
for the LTDC driver. Also, in the .ioc config, LTDC has the framebuffer address set to 0x20000000.
The 750kb size is 800x480x2 bytes.
The second framebuffer is declared in Core/Src/lvgl_port.c and is the same size.
The display is capable of 24 bit color depth but LTDC is configured as 16 bits for reduced memory usage.
USE_HAL_LTDC_REGISTER_CALLBACKS has been enabled in Core/Inc/stm32u5xx_hal_conf.h to support the
LVGL LTDC driver.
If you find any issues with the development board feel free to open an Issue in this repository. For LVGL related issues (features, bugs, etc) please use the main lvgl repository.
If you found a bug and found a solution too please send a Pull request. If you are new to Pull requests refer to Our Guide to learn the basics.
