earthground: A Python Library for Creating Software-Defined Electrical Designs

Overview

Earthground encompasses a comprehensive suite of tools and libraries aimed at facilitating software-defined electronic schematics.

Documentation

Getting Started

Setup

pip install -r requirements.txt

Simple Example - Resistor Divider

import common.components as cmp
import common.schematic as sch_lib
import common.standard_values as sv
import library.headers.connectors as conn_lib

# Setup the schematic page
schematic = sch_lib.Design("Resistor Divider Example")
schematic.default_passive_size = "0603"

# Create the components
r1, r2 = sv.find_closest_ratio(5 / 3.3)  # finds closest values in E24
r_top = schematic.add_component(cmp.Resistor(f"{r1}k"))
r_bottom = schematic.add_component(cmp.Resistor(f"{r2}k"))
input_connector = schematic.add_component(conn_lib.standard_0_1_inch_header(pin_count=2))
output_connector = schematic.add_component(conn_lib.standard_0_1_inch_header(pin_count=2))

# Connect them and print schematic to console
schematic.connect([r_top.pins[1], input_connector.pins[1]], "SIG_5V0")
schematic.connect([r_top.pins[2], r_bottom.pins[1], output_connector.pins[1]], "SIG_3V3")
schematic.connect([input_connector.pins[2], r_bottom.pins[2], output_connector.pins[2]], "GND")
schematic.print()

Project Walkthrough - 32 Port I/O Expander

Read the example

• Located in examples/io_expander_example.py
• Run using: python3 -m examples.io_expander_example

Advantages of Software-Defined Circuits

Extensive Tooling

Text-based schematics means engineers can leverage existing software engineering tooling to create error-free designs faster

• Use version control software to save progress, create easy-to-read diffs between versions, and do design review
• Use dev tooling like CI/CD tools to automatically run design rule checkers and application-specific validators to ensure a correct design
• One-click releases - Automatically generate Gerbers, pick-n-place files, cost rollups, power budgets, bringup test plans

Modular

Finally have stable and correct part libraries and circuits that you can quickly piece together to create complex projects quickly

Extendable

Earthground can be extended to many purposes because it's written in Python

• If your PCB being connecting to another PCB via harness, you could write an exporter so your favorite harness program always has the latest design
• If there's a microcontroller in your design, you could add an exporter to generate a BSP package or Micropython definition from the schematic that will automatically create a new file on every revision
• If you are concerned about supply chain and components going out-of-stock, you could have your schematic track which components are in stock and define part variations

Powerful

With a Python backend, it's simple to create powerful component libraries that allow you to create complex designs quickly. Just read the datasheet once and you are good to go

• Abstract complex hardware configuration pins to the component library so your schematics are highly readable (and therefore easily reviewable)
• Rather than noting the position of every configuration on a microcontroller and matching it to the datasheet for every design review you do. You could review your component definition once then in every design do readable things like mcu.set_boot_location(mcu.EXTERNAL_FLASH) to easily catch issues
• Quickly set addresses are know they are right:

  for i, device in enumerate(i2c_devices):
  device.set_i2c_address(i)
  

• Add validators for datasheet errata and buried issues so if anyone uses a component in a nonrecommended way on the current design or any future design, Earthground will flag it.
• Parameterize passive component selection for ICs
• For buck converters, Earthground can automatically size inductors based on datasheet parameters
• For LDOs, given an output voltage, Earthground will select the feedback resistors, round them to E24 values, and warn you if the result output voltage is beyond a specified percentage

State of the Project

This an actively worked on project. Currently there's no way to finish layout. I'm working on a KiCAD exporter so you can import the netlist and footprints to KiCAD and do layout there. The final goal is to incorporate a layout editor into the project.