XGSoC

FPGA based system on chip.

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

Features

• RISC-V (RV32IM)
• UART (1000000-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 (RGB565)
• Graphite 2D/3D graphics accelerator (textured triangles)
• PS/2 Keyboard
• PS/2 Mouse
• USB host for keyboard and mouse (experimental)
• 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-arm64-20240810 and xpack-riscv-none-elf-gcc-14.2.0-1-darwin-arm64.

Getting Started

Clone and Update

Clone

git clone --recurse-submodules https://github.com/danodus/xgsoc.git
cd xgsoc

If the repository has been cloned without the --recurse-submodules option, do the following:

git submodule update --init

Update

git pull
git submodule update --recursive

Getting Started on ULX3S

cd rtl/ulx3s
make clean;make CONF=<conf> VIDEO=<video mode> prog # for example, CONF=bvkm VIDEO=vga (see below)
cd ../../src/hello
make run SERIAL=<serial device>
picocom -b 1000000 <serial device>

Configurations

Identifier	Description
b	Base (UART, SD Card)
v	Video
g	Graphite
k	PS/2 Keyboard
m	PS/2 Mouse
u	USB Host (*)

(*) USB host requires a CPU clock of 48 MHz instead of the default 50 MHz.

By default, the configuration is bvgkm.

The following video modes are available:

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

By default, the video mode is vga.

System Simulation

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

Programs

To upload and run the program to the FPGA platform:

cd src/<program name>
make run SERIAL=<serial device>
picocom -b 1000000 <serial device>

The following programs are available:

Name	Description	Min. Config.
test_mem	Test memory	b
test_fs	Test filesystem (SD card content erased)	b
bench_dhrystone	Benchmark Dhrystone	b
write_sd_image	Write bootable SD card image (see section below)	b
hello	Hello world example	b
factorial	Factorial example	b
sinus	Sinus example	b
forth	Forth language	b
lua	Lua language	b
test_ps2_kbd	Test PS/2 keyboard	bk
test_ps2_mouse	Test PS/2 mouse	bm
test_usb	Test USB host	bu
test_video	Test video display	bv
test_graphite	Test graphite subsystem	bvg

Write Bootable Image

• Insert the SD card
• Open a serial terminal
• Start the image writer utility:

cd src/write_sd_image
make run SERIAL=<serial device>

• Send the data to write:

cd ../<program name>
make write SERIAL=<serial device>

Press a key when completed. The SD card image will automatically be read and executed unless a key is sent via UART during the first seconds of the boot process.

Acknowledgements

• The SoC is based on the Oberon project for the ULX3S available here: https://github.com/emard/oberon
• The USB host is based on usb_host available here: https://gitlab.com/pnru/usb_host