Lattice Propel (RISC-V RX) Build Guide

RISC-V RX overview

The Lattice RISC-V RX soft IP is a 32-bit RISC-V core which supports AXI interfaces. It bundles a PLIC (Platform Level Interrupt Controller), a CLINT (Core Local Interrupter), and a watchdog, and supports the RV32IMACF instruction set. The core offers three privilege modes (Machine, Supervisor, User), multiple processor modes (Advanced, Balanced, Lite), and includes instruction/data caches plus a JTAG (IEEE 1149.1) debug interface. Because most of our IPs available in the HDL repository, use AXI-Lite control interface and our DMA also uses the AXI interface, this is the RISC-V variant we currently support on Lattice FPGAs. See the vendor page for details: RISC-V RX CPU IP | Lattice Semiconductor (latticesemi.com)

Scope

Bare-minimum steps to build and run a Lattice RISC-V RX design. Tested with the build tools provided in Propel SDK 2024.2 and the RISCV-RX latticesemi.com:ip:riscv_rtos:2.5.0 core used by projects/ad738x_fmcz.

Install & Inputs

  1. Install the Propel SDK (includes GCC, srec_cat, OpenOCD).

  2. Export a hardware package from your HDL project (sge directory or sge.zip). Drop it next to the project Makefile.

  3. (Optional but recommended) Generate the FPGA bitstream (*.bit) separately via Propel Builder/Radiant from the matching HDL design hosted at the HDL repository so it is ready for programming time.

PATH Setup

Add the Propel toolchain to your PATH before running make by prepending the three tool directories explicitly:

export PATH="/opt/lscc/propel/2024.2/sdk/riscv-none-embed-gcc/bin":$PATH
export PATH="/opt/lscc/propel/2024.2/sdk/tools/bin":$PATH
export PATH="/opt/lscc/propel/2024.2/openocd/bin":$PATH

Verify with which riscv-none-embed-gcc srec_cat openocd to ensure the tools are visible.

Build only

cd projects/ad738x_fmcz
# when the sge assets already live in the project root
make PLATFORM=lattice
# automatic platform when the sge assets already live in the project root
make
# explicitly point to BSP assets that live elsewhere
make HARDWARE=/path/to/your/sge

The lattice platform is auto-selected only when the project root already contains an sge directory or sge.zip, or when the HARDWARE variable points to those assets. When a zip is detected, it is unpacked into <project>/sge. When HARDWARE points to an external sge directory, that directory is copied into <project>/sge as the canonical local runtime location. After the first make HARDWARE=<non_project_root>/sge or make HARDWARE=<non_project_root>/sge.zip, plain make can be used for subsequent runs.

  • Output artifacts:

    • build/ad738x_fmcz.elf (CPU executable)

    • build/ad738x_fmcz.map (linker map)

    • build/ad738x_fmcz.lst (objdump/listing)

    • build/ad738x_fmcz.siz (size report)

    • build/ad738x_fmcz.bin (raw binary image)

    • build/ad738x_fmcz.mem (byte-swapped memory image)

Build & Program

  1. Use Lattice Radiant Programmer to load the FPGA bitstream (*.bit) generated from the matching HDL design (for reference see the no-OS companion HDL repository). This must happen before loading the CPU binary.

  2. Run make run to upload the .elf with OpenOCD. The plain command works only when the project root contains the sge folder (or an auto-unpacked sge.zip). Otherwise point HARDWARE to the folder that holds the exported BSP (sge directory or sge.zip).

    # when the sge assets already live in the project root
make run PLATFORM=lattice
# automatic platform when the sge assets already live in the project root
make run
# explicitly point to BSP assets that live elsewhere
make run HARDWARE=/path/to/your/sge

    Both recipes halt the CPU, load the ELF, and resume execution.

Clean

Use one of the following cleanup targets, depending on scope:

  • make clean: removes compiled artifacts (*.o, *.elf, etc.)

  • make reset: removes the entire build directory

  • make reset-all: runs reset and also removes <project>/sge

Examples:

# remove compiled artifacts
make clean PLATFORM=lattice
make clean
make clean HARDWARE=/path/to/your/sge

# remove the entire build directory
make reset PLATFORM=lattice
make reset
make reset HARDWARE=/path/to/your/sge

# remove build directory and the local copied/extracted sge folder
make reset-all PLATFORM=lattice
make reset-all
make reset-all HARDWARE=/path/to/your/sge