Getting Started

Install RyuSim, compile your first design, and run tests with cocotb.

Prerequisites

Install the required build tools for your distribution. The installer will warn if these are missing, but installing them first avoids interruption.

Ubuntu / Debian

sudo apt install clang cmake python3 python3-pip

Fedora / Rocky Linux 10+

sudo dnf install clang cmake python3 python3-pip

Rocky Linux / RHEL 9

sudo dnf install epel-release && sudo /usr/bin/crb enable && sudo dnf install clang cmake python3 python3-pip

Install RyuSim

curl -fsSL https://ryusim.seiraiyu.com/install.sh | bash

The installer auto-detects your architecture and glibc version. See Downloads for the full list of supported distributions.

Compile your first design

Create a simple counter design:

module counter (
  input  logic       clk,
  input  logic       rst,
  output logic [7:0] count
);
  always_ff @(posedge clk) begin
    if (rst)
      count <= 8'h0;
    else
      count <= count + 1;
  end
endmodule

Compile it:

ryusim compile counter.sv --top counter

Run with cocotb

RyuSim v1 is a VPI-only simulator. Write testbenches in Python using cocotb.

Note: RyuSim support is not yet in upstream cocotb. Install cocotb from the Seiraiyu fork first — see Downloads for details.

Create a testbench file test_counter.py:

import cocotb
from cocotb.triggers import RisingEdge, FallingEdge
from cocotb.clock import Clock

@cocotb.test()
async def test_counter_counts(dut):
    """Check that the counter increments on each clock edge."""
    cocotb.start_soon(Clock(dut.clk, 10, unit="ns").start())

    dut.rst.value = 1
    await RisingEdge(dut.clk)
    await FallingEdge(dut.clk)
    dut.rst.value = 0

    for _ in range(10):
        await RisingEdge(dut.clk)

    await FallingEdge(dut.clk)  # let NBA updates settle
    assert dut.count.value.to_unsigned() == 10, f"Expected 10, got {dut.count.value.to_unsigned()}"

Create a Makefile in the same directory:

SIM            ?= ryusim
TOPLEVEL_LANG  := verilog

VERILOG_SOURCES = $(PWD)/counter.sv
TOPLEVEL        = counter
COCOTB_TEST_MODULES = test_counter

include $(shell cocotb-config --makefiles)/Makefile.sim

Run the test:

make

cocotb will compile the design with RyuSim, load the VPI testbench, and report results. See the cocotb documentation for triggers, coroutines, bus drivers, and more.