A limited Python/cocotb interface to the Xilinx Vivado Simulator simulator. Based on cocotb-stub-sim.

Proof of Concept – expect limitations (see below).

• Only top-level ports are accessible (simulator limitation).
• Only the Timer trigger is supported (simulator limitation).
• Setting signal values is immediate (setimmediatevalue behavior).
• Only Verilog top-levels are supported (VHDL support planned).
• Direct access to the XSI interface is available.

pip install cocotb-vivado==0.0.3 (for VIVADO <= 2022.2)
pip install cocotb-vivado (for VIVADO >= 2023.1)

import subprocess

import cocotb_vivado
import cocotb
from cocotb.triggers import Timer

@cocotb.test()
async def simple_test(dut):
    dut.clk.value = 0
    await Timer(10, units="ns")
    dut.clk.value = 1
    await Timer(10, units="ns")
    assert dut.out.value == 1

def test_simple():
    subprocess.run(["xvlog", "tb.v"])
    subprocess.run(["xelab", "work.tb", "-dll"])

    cocotb_vivado.run(module="test_simple", xsim_design="xsim.dir/work.tb/xsimk.so", top_level_lang="verilog")

See testes/test_simple.py for full example.

See the tests folder for examples.

source ../Vivado/202X.X/settings64.sh
export LD_LIBRARY_PATH=$XILINX_VIVADO/lib/lnx64.o
pytest -s

Extra feature: One does not need to recompile the project when running/changing tests .

You can use XSI interface directly see tests/test_xsi.py for an example.

In order to use cocotb extension like cocotbext-axi one needs to mock the triggers (XSI limitations) by creating global clock timer and synchronizes all trigger events to it. See tests/test_axil.py for an example.

In order order to simulate full design you need create design, export_simulation files compile, elaborate and run. See tests/fw.tcl and tests/test_fw.tcl for an example.

You can dump vcd file with verilog syntax in your testbench:

initial begin
    $dumpfile("test.vcd");
    $dumpvars(0);
end

We'd like to thank our employer, Dectris for supporting this work.