GHDL Interactive Simulation

This is an interactive test bench for a simple VHDL adder. It uses GHDL to elaborate/run the simulation. It is coded in Python using the Cocotb library to implement the GUI test bench as a VPI plugin and pygame to render the GUI.

Sample VHDL

library ieee;
  use ieee.std_logic_1164.all;
  use ieee.numeric_std.all;

entity adder is
  generic (
    DATA_WIDTH : positive := 4);
  port (
    A : in    unsigned(DATA_WIDTH-1 downto 0);
    B : in    unsigned(DATA_WIDTH-1 downto 0);
    X : out   unsigned(DATA_WIDTH downto 0));
end entity adder;

architecture rtl of adder is
begin

  add_proc : process (A, B) is
  begin
    X <= resize(A, X'length) + B;
  end process add_proc;

end architecture rtl;

Resulting GUI

Requirements

• Python (tested using version 3.9)
• GHDL Simulator
• GNU Make (build-essential package on *nix)

Running

*nix and Mac OS

• Get Python dependencies first...

pip install -r requirements.txt

• Then in the test directory...

make

Windows

Sorry, but I need to create a docker image and instructions...

Credits

Many thanks to the GHDL VPI virtual board project for the inspiration and the images (which I shamelessly borrowed given how artistically challenged I am).