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Developing RISC-V Applications

This page covers standard RISC-V applications that do not use Signaloid's UxHw® distribution-extended computation. If your application needs to perform arithmetic on probability distributions, see Developing UxHw Applications instead.

You program the built-in Signaloid SoC (ISA/ABI: rv32i / ilp32) in C and flash your binaries over the SD interface. See the shared operational model for the coprocessor workflow, and Getting Started for the end-to-end flow.

The Signaloid SoC is based on the open-source PicoRV32 project, extended to support a subset of Signaloid's distribution-extended computation, as well as communication with the host over the SD interface.

Install the RISC-V GNU cross-compilation toolchain​

Compiling applications for the Signaloid SoC requires the open-source RISC-V GNU toolchain, built for the rv32i / ilp32 configuration.

The pre-built binaries in the RISC-V GNU toolchain releases do not contain the standard C libraries compiled for the rv32i / ilp32 configuration that the Signaloid SoC needs. Using them results in fatal compilation errors. Build the toolchain from source using the steps below.

A. Clone the toolchain​

git clone --recursive https://github.com/riscv-collab/riscv-gnu-toolchain.git

B. Install GCC (macOS 14+ only)​

This step is required on macOS 14+ with Apple clang 15.0.0. Skip it on earlier macOS versions and on Linux.

Install gcc-mp-13 and g++-mp-13:

sudo port install gcc13

Set CC and CXX so the configure step picks them up:

export CXX=g++-mp-13 CC=gcc-mp-13

C. Configure​

Configure the build for the rv32i ISA with the ilp32 ABI. Set --prefix to your desired installation directory. --disable-gdb skips building gdb. Remove it if you want gdb.

./configure --prefix=/path/to/installation/dir --with-arch=rv32i --with-abi=ilp32 --disable-gdb

D. Build​

make

Optionally parallelize with -j, for example make -j4. The build takes several minutes. When it finishes, the toolchain is in the directory you passed to --prefix.

Compile your application​

Example Makefiles for the Signaloid SoC are in the signaloid-soc-examples/ directory of the C0-microSD-Hardware repository. Edit each Makefile to point at your toolchain installation path before building.

Flash and run​

The Signaloid SoC initializes its memory from the first 128 KiB of the flash user-data sector, so flash your binary with the -u option while the device is in Bootloader mode, then switch to Signaloid SoC mode and power-cycle:

sudo python3 ./C0_microSD_toolkit.py -t /dev/sdb -b program.bin -u

See Getting Started for the full identify → flash → run sequence.

Host application​

To communicate with the application running on the C0-microSD, you need a host application that runs on the host system and exchanges data with the device application over the SD interface. See Host Interface and Protocol for the communication model, the host-side block offsets, and a worked host-application example. The demo applications in the Signaloid-C0-microSD-Demo repositories serve as examples of how you can build a host application.

Next steps​

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