Welcome to PyGears


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HW Design: A Functional Approach

PyGears is a free framework that lets you design hardware using high-level Python constructs and compile it to synthesizable SystemVerilog or Verilog code. There is a built-in simulator that lets you use arbitrary Python code with its vast set of libraries to verify your hardware modules. PyGears makes connecting modules easy, and has built-in synchronization mechanisms that help you build correct parallel systems.

from pygears import gear, Intf, alternative
from pygears.lib import decouple, fmap, union_collapse, trunc
from pygears.typing import Fixp, ceil_pow2, Tuple
from pygears.lib import flatten, priority_mux, replicate, once

def prefill(din, *, num, dtype):
    fill = once(val=dtype(0)) \
        | replicate(num) \
        | flatten

    return priority_mux(fill, din) \
        | union_collapse

def echo(din: Fixp, *, feedback_gain, sample_rate, delay):
    sample_dly_len = round(sample_rate * delay)
    fifo_depth = ceil_pow2(sample_dly_len)
    feedback_gain_fixp = din.dtype(feedback_gain)

    dout = Intf(din.dtype)

    feedback = dout \
        | decouple(depth=fifo_depth) \
        | prefill(dtype=din.dtype, num=sample_dly_len)

    feedback_attenuated = trunc(feedback * feedback_gain_fixp, t=din.dtype)

    dout |= trunc(din + feedback_attenuated, t=dout.dtype)

    return dout

Python functions model hardware modules, where function arguments represent module inputs and parameters. Example echo module has a single input port called samples where data of arbitrary signed fixed-point type Fixp can be received. Other three parameters feedback_gain, sample_rate and delay are compile time parameters.

def echo(samples: Fixp, *, feedback_gain, sample_rate, delay):

Arbitrary Python code can be used in modules at compile time, for an example to transform input parameters:

sample_dly_len = round(sample_rate * delay)
fifo_depth = ceil_pow2(sample_dly_len)
feedback_gain_fixp = samples.dtype(feedback_gain)

Rest of the echo function code describes the hardware module for applying echo audio effect to the input stream.


Modules are instantiated using function calls: decouple(dout, depth=fifo_depth), which return module output interfaces that can in turn be passed as arguments to other module functions in order to make a connection between the modules. For conveniance the pipe "|" operator can be used to pass output of one function as argument to the next one. This was used to connect the output of decouple to prefill ("\" is used just to split the line visually):

feedback = decouple(dout, depth=fifo_depth) \
    | prefill(dtype=samples.dtype, num=sample_dly_len)

Again, the echo function returns its output interfaces which is then used to establish the connection with the next module that received the echo output stream:

def echo(...):
    return dout

Built-in simulator makes it easy to test and verify the modules while drawing power from the Python vast ecosystem of libraries. For an example, use Python built-in audioop library to read WAV files into an input samples stream for the echo module, and then visualise the input and output waveforms using matplotlib:


Speedup the simulation by configuring PyGears simulator to use open-source Verilator to simulate hardware modules, or some of the proprietary simulators like Questa, NCSim or Xsim. Implement any part of the system in a standard HDL and debug your design by inspecting the waveforms for an example in open-source wave viewer GTKWave


Checkout Echo example description for more in depth information about the echo example.

Installation instructions

Install PyGears package with the Python package manager. On Linux distributions, depending on how your Python was installed you might get an error and need to prefix the command with sudo:

pip3 install pygears

For more detailed installation instructions (including how to install additional software) checkout Installation page.

Read the documentation

PyGears documentation

Checkout the examples

Library of standard modules

Echo: Hardware module that applies echo audio effect to a continuous audio stream.

Tests: Contain many examples on how individual PyGears components operate


Special thanks to the people that helped develop this framework:

  • Andrea Erdeljan

  • Damjan Rakanović

  • Nemanja Kajtez

  • Risto Pejašinović

  • Stefan Tambur

  • Vladimir Nikić

  • Vladimir Vrbaški

  • Stefan Stanić

  • Filip Dojčinović

  • Aleksa Knežević

  • Alena Delkić

  • Nataša Samac

  • Jovan Stojanović

  • Mirko Jeličić

  • Stefan Sredojević

  • Dejan Marković

  • Tim Ling

In order to contribute, pull your copy from github repository and create a pull request.