Bare metal programming on the RED-V Thing Plus board (SiFive RISC-V FE310 SoC).

This repository implements an entirely manually-written, pure bare metal Blinky Project for the SiFive RISC-V FE310 SoC (on the RED-V Thing Plus board).

Features include:

• CPU, power, chip, clock and PLL initialization,
• timebase derived from mtimer,
• blinky LED show with adjustable frequency,
• implementation in C99 with absolute minimal use of assembly.

Clear and easy-to-understand build systems based on either GNUmake or CMake complete this fun and educational project.

This repository provides keen insight on starting up a bare metal SiFive RISC-V controller. It emphasizes simplicity and independence from monolithic toolchains through its lightweight, self-written implementation.

The application boots from a tiny startup code in the boot ROM.

Following low-level chip initialization, the program jumps to the main() subroutine. Here the timer interrupt is setup for LED blinky.

The adjustable LED-phase (its half-period) can be tuned to provide a rudimentary, visible blinky LED show. The timebase for blinky is based on the mtimer interrupt handler.

Blinky running on the target is shown in the image below.

Build on *nix* is easy using gcc-riscv32-unknown-elf

Both Make and Cmake can be used to build the Application:

cd RED-V_SiFive_RISC-V_FE310_SoC

./Rebuild.sh

mkdir Output && cd Output
cmake -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchain-unix.cmake .. && make

The build results including ELF-file, HEX-mask, MAP-file and assembly list file are created in the Outputdirectory.

If gcc-riscv32-unknown-elf is not installed, it can easily be obtained from embecosm. Add the path of the RISC-V GCC tools' bin folder to $PATH in the usual *nix way.

CI runs on pushes and pull-requests with simple build(s) including result verification on ubuntu-latest and macos-latest using GitHub Actions.

• The source and build code written for this repo is licensed under The Unlicense.
• Also the system-register file riscv-csr.h, originally from five-embedded, is licenced under The Unlicense.