Launching RISC-V K1921VG015: toolchain and OpenOCD

Setting Up Toolchain and OpenOCD for Running RISC-V on K1921VG015

A demo project is launched on development boards with the K1921VG015 microcontroller based on RISC-V architecture. This requires a DirtyJTAG JTAG adapter, the riscv-gnu-toolchain compiler, and OpenOCD with patches from NIIET. The work is done in WSL on Windows 11 with Debian 13 (trixie).

Installing basic packages ensures the toolchain can be built:

sudo apt install autoconf automake autotools-dev curl python3 python3-pip python3-tomli libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat1-dev ninja-build git cmake libglib2.0-dev libslirp-dev libncurses-dev libusb-1.0-0-dev libusb-1.0-0 cmake

Building the riscv-gnu-toolchain Compiler

Clone the repository with recursive submodules:

git clone --recursive https://github.com/riscv/riscv-gnu-toolchain
cd riscv-gnu-toolchain
./configure --prefix=/opt/riscv --enable-multilib
sudo make

The --enable-multilib flag enables support for RV32 and RV64. Building as root ensures installation in /opt/riscv. After this, add /opt/riscv/bin to PATH to access riscv64-unknown-elf-gcc and other tools.

Compiling OpenOCD with DirtyJTAG Support

Use the OpenOCD fork from NIIET (commit ed64294116beb6bc335a6c5809b46a87add8042a):

git clone --recursive https://gitflic.ru/project/niiet/openocd.git
cd openocd/
git apply --verbose 0001-jtag-add-support-for-adapter-DirtyJTAG.patch
git apply --verbose 0002-fix-correct-calloc-argument-order-for-GCC-14-compati.patch
./bootstrap
./configure --prefix=/usr/
make -j$(nproc)
sudo make install

Patch 0001 adds the driver for DirtyJTAG. Patch 0002 fixes the calloc argument order for compatibility with GCC 14. Copy the k1921vg015.cfg configuration to /usr/share/openocd/scripts/target/ — chip support is not included in the base NIIET version.

Building and Flashing the Demo Project

The demo is generated in Syntacore Development Toolkit, with CMakeLists.txt added manually. Build it:

mkdir build
cd build
cmake ../CMakeLists.txt
make

The resulting Run_leds.bin is ready for loading. In WSL, connect the USB device:

usbipd list  # Find DirtyJTAG BUSID, e.g., 1-3
usbipd attach --wsl --busid 1-3

Launch the firmware via OpenOCD:

sudo openocd -f interface/dirtyjtag.cfg -f target/k1921vg015.cfg -c "program Run_leds.bin 0x80000000 verify reset exit"

This command programs at address 0x80000000, verifies integrity, resets, and exits. On pure Linux, skip the usbipd step.

Key setup steps in a list:

• Install Debian packages for the toolchain.
• Build the multilib compiler in /opt/riscv.
• Patching and compiling OpenOCD with DirtyJTAG support.
• Adding k1921vg015.cfg to scripts.
• CMake project build and USB attach in WSL.
• Flashing with verify and reset.

What's Important

• --enable-multilib is essential for RV32/RV64 on a single toolchain.
• OpenOCD patches are critical: DirtyJTAG and GCC14-calloc.
• Load address 0x80000000 is standard for K1921VG015.
• WSL requires usbipd for JTAG access.
• Config k1921vg015.cfg is added manually.

Further debugging involves studying the chip architecture through similar toolchain steps.

— Editorial Team