Graphite

Graphite is a FPGA based open source system with 2D/3D graphics acceleration.

Documentation

The documentation is available here: https://danodus.github.io/graphite/

Features

The system has the following features:

• RISC-V (RV32I + Graphite extension)
• UART (1000000/2000000-N-8-1)
• SDRAM (32MiB shared between CPU and video)
• Set associative cache (4-way with LRU replacement policy)
• VGA (60 Hz), 480p (60Hz), 720p (60Hz) or 1080p (30Hz) HDMI video output with framebuffer (ARGB4444)
• 2D/3D graphics accelerator (textured triangles)
• PS/2 keyboard
• PS/2 mouse
• SD Card with hardware SPI

Requirements

• OSS CAD Suite (https://github.com/YosysHQ/oss-cad-suite-build) (*)
• xPack RISC-V Embedded GCC (https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases) (*)
• Python3 with the following PIP3 packages installed: pyserial
• picocom
• SDL2 (for simulation only)

(*) Extract and add the bin directory to the path.

Note: Tested with oss-cad-suite-darwin-arm64-20240201 and xpack-riscv-none-elf-gcc-13.2.0-2-darwin-arm64.

Getting Started on ULX3S

cd soc/src/bios
make
cd ../../rtl/ulx3s
make clean;make VIDEO=<video mode> CPU_SPEED=<cpu speed> prog
cd ../../src/examples/test_graphite
make run SERIAL=<serial device>
picocom -b 2000000 <serial device>

and press 'h' for help.

The following video modes are available:

Video Mode	Description
vga (default)	640x480 60Hz
480p	848x480 60Hz
720p	1280x720 60Hz
1080p	1920x1080 30Hz

The following CPU speeds are available:

CPU Speed	Description
slow (default)	40MHz
fast	50MHz

System Simulation

cd soc/src/examples/test_video
make
cd ../../../../soc/rtl/sim
make run PROGRAM=../../src/examples/test_video/program.hex

Graphics Accelerator Simulation

cd rtl/sim
make run

• Press 1 to select the cube model;
• Press 2 to select the teapot model;
• Press W/A/S/D and arrows to move the camera;
• Press SPACE to start/stop the rotation of the model;
• Press TAB to enable/disable the wireframe mode;
• Press T to enable/disable texture mapping;
• Press L to increase the number of directional lights;
• Press G to enable/disable Gouraud shading.

Acknowledgements

• The SoC is based on the Oberon project for the ULX3S available here: https://github.com/emard/oberon
• The CPU is based on icicle v1 available here: https://github.com/grahamedgecombe/icicle/tree/v1