Use python3 -m cocotbpynq.sample to see sample
cocotbpynq is an extension of cocotb that allows for your PYNQ code to be seamlessly used for simulation. This allows you to debug the AXI transactions that occur between the PL and PS. Currently, there is support for the Pynq Z1 board, although it shouldn't be much different, (if at all), to adapt this code to other PYNQ-compatible FPGAs.
Once Python is installed, install cocotbpynq using the following:
pip install cocotbpynq
Alternatively, clone the repo and use it as an install directory for the most up-to-date version:
https://github.com/watcag/cocotb-pynq
There is a sample directory, src/cocotbpynq/sample that shows everything needed make use cocotbpynq yourself. It even includes a hardware hand-off file. Specifically, you will want to reference cocotb_runner.py and adapted.py for development of your own tests.
You can run this sample project mentioned above (after installing cocotbpynq) with:
python3 -m cocotbpynq.sample
Note that verilator is used in the sample project, so you will need verilator installed for this to work out of the box.
The original.py and original_vs_adapted.diff files are there to illustrate how few changes are needed to adapt PYNQ code ALSO be simulation ready. The adaptation should allow you to either run the cocotb_runner.py file to run a simulation, or continue to run the adapted file on a PYNQ-compatible board.
The sample is meant to illustrate a simple example with one AXI-Lite port(MMIO), one AXI-Stream read port (DMA send), and one AXI-Stream write port (DMA recv). The circuit performs a simple y = ax²+bx+c operation, where a, b, and c are all constants that can be modified/read using the MMIO port at addresses 0x10, 0x18, and 0x20 respectively, and x and y are AXI-Stream write/read ports respectively.
HWH file can be generated independantly of bitstream using the following Vivado CLI command:
generate_target all <block design file>
This can be used to circumvent the need to ever to bitstream generation. Unlike bitstream generation, this command only needs to be run if the block diagram is updated.
This paper relies was built on the back of cocotb, which is an amazing library in its own right.
It also aims to mimic some features from PYNQ. Naturally, the PYNQ repo was a large source of inspiration/reference for much of the content in this repo.
Our paper was presented at the 35th International Conference on Field-Programmable Logic and Applications(FPL 2025). The conference paper can be found here: < Proceedings not available yet >