The default settings in the riscv-tools build scripts will build a compiler, assembler and linker that can target any RISC-V ISA, but the libraries are built for RV32G and RV64G targets. Follow the instructions below to build a complete toolchain (including libraries) that target a pure RV32I CPU.

The following commands will build the RISC-V gnu toolchain and libraries for a pure RV32I target, and install it in /opt/riscv32i:

# Ubuntu packages needed:
sudo apt-get install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev \
        libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc

sudo mkdir /opt/riscv32i
sudo chown $USER /opt/riscv32i

git clone https://github.com/riscv/riscv-gnu-toolchain riscv-gnu-toolchain-rv32i
cd riscv-gnu-toolchain-rv32i
git checkout 7e48594
git submodule update --init --recursive

mkdir build; cd build
../configure --with-arch=RV32I --prefix=/opt/riscv32i
make -j$(nproc)

The microcontroller is composed by a 32b RISC-V core, a 4KB SRAM, a 10b ADC, a 12b DAC, 8 GPIO, and two SPI interfaces (master and slave). All the modules are conneted using two differente buses: AXI4 and APB.

The directory tree is:

mriscv/mriscv_axi/ADC_interface_AXI -----> ADC interface with the AXI4 bus

mriscv/mriscv_axi/AXI_SP32B1024 -----> SRAM memory interface

mriscv/mriscv_axi/DAC_interface_AXI -----> DAC interface with the AXI4 bus

mriscv/mriscv_axi/axi4_interconnect -----> the AXI4 bus

mriscv/mriscv_axi/impl_axi -----> the microcontroller

mriscv/mriscv_axi/spi_axi_master -----> master SPI used for programming

mriscv/mriscv_axi/spi_axi_slave -----> slave SPI used for data adquisition

Also, there are a PCB design for the development board, including circuits for sensing analog signals and the capability to use external clocks. The design is in mriscv/board