Calling Python from Verilog via VPI

This is a demonstration of how to call a routine in Python from Verilog using a C++ VPI hook intermediary layer.

Configuration

Before compiling, make sure to update the following variables in Makefile:

• PYTHON_LIB_DIR - should point at the directory containing the libpython shared library for your installation.
• PYTHON_LIB_NAME - should be the name of your Python library (excluding the lib prefix and .so/.dylib suffix).
• ICARUS_LIB_DIR - should point at the directory containing libvpi.a, provided with Icarus Verilog.
• ICARUS_INC_DIR - should point at the directory containing header files for Icarus Verilog (specifically vpi_user.h).
• ICARUS_VPI_LIB - should be the name of the VPI library provided with Icarus Verilog (excluding the lib prefix and .a/.so suffix).

To Run the Demo

Once you've adjusted the configuration as above, execute make run to run the demo:

$> make run
# Creating directory output/obj
# Compiling demo.cpp -> demo.o
# Linking objects to form demo.vpi
# Compiling Verilog
About to call C++ from Verilog through VPI
About to call Python from C++ via pybind11
This is from Python - calling C++: 3

What's Going on Here?

The following steps are happening:

• In demo.v a call is made to a $demo system task.
• When $demo is called, it actually executes a VPI function from demo.cpp called trampoline_calltf.
• The trampoline function then calls do_something - which is a function imported from the demo.py.
• The do_something function in demo.py then calls back to a function exposed from C++ called add (see demo.cpp lines 19-22) again using pybind11.