digilogic

A digital logic simulation and schematic capture program.

• With the following features:
  • Wire auto-routing
  • Alignment based snapping (rather than grid based)
  • First class dark mode support
  • Cross platform (Windows, Mac, Linux)
  • Import from verilog via Yosys with auto layout and routing
  • Import from H. Neeman's Digital
  • Written in Rust
• Inspirations:
  • Issie (github.com/tomcl/issie)
  • Digital Logic Sim (github.com/SebLague/Digital-Logic-Sim)
  • Digital (github.com/hneemann/Digital)
  • LogiSim Evolution (github.com/logisim-evolution/logisim-evolution)

Status

This is under heavy development.

The only editing feature implemented so far is moving components around.

Currently, importing a Digital circuit works as long as it:

• Contains no rotated components
• Only uses Inputs, Outputs, And, Or, Xor and Not
• All wires/components are 1 bit wide
• Contains no embedded circuits

Yosys import works with similar constraints:

• Only produces And, Or, Xor and Not gates
• Only a single module with input and output ports (but no inout ports)

Building / Running

Install rust via rustup, then:

cargo run

To run the simulation server (required to simulate circuits) run this in a separate terminal:

cargo run -- server

Yosys Import

Use the following command to generate an unoptimized yosys file for import:

yosys -p "read_verilog <INPUT_VERILOG>.v; hierarchy -auto-top; proc; opt_clean; fsm -expand; memory -nomap; wreduce -memx; opt_clean; write_json <OUTPUT_FILE>.yosys"

To have yosys do some basic optimizations on the verilog, use this command:

yosys -p "read_verilog <INPUT_VERILOG>.v; hierarchy -auto-top; proc; opt; fsm -expand; memory -nomap; wreduce -memx; opt; write_json <OUTPUT_FILE>.yosys"

If it crashes/errors on loading, it likely contains components that have not been implemented yet. Simplify your verilog until it works.

Code Overview

The architecture is kind of an onion-like layered architecture with core at the center, and the main crate on the outermost layer. But there's a few lumps where simulation, automatic routing and layout, and other features live. More information can be found in the docs folder.

This app is built like a game, using game engine technology. We're using Bevy ECS to allow the code to be more modular. We also use Bevy App Plugins. I highly recommend reading through the Unofficial Bevy Cheatbook's chapter on the Bevy Programming Framework which covers the fundamental building blocks we're using.

Most crates in the crates folder are also bevy plugins. Anything that's used by several crates should be moved into core rather than building a spider web of dependencies between crates that will be difficult to untangle later.

For windowing and UI we use eframe and egui. For all graphics in the main schematic viewport, we use vello in order to render as much on the GPU as we can (this is why it's fast, even in debug mode).

.
├── assets -- Images, fonts and other resources
└── crates -- Main crates, set up as a mono-repo of sorts
    ├── digilogic -- Main crate with UI, drawing and window management
    │   ├── assets
    │   │   ├── schemalib -- SVG symbols from the wonderful schemalib project
    │   │   │   └── symbols
    │   │   └── testdata -- Some example project files for testing
    │   └── src -- Source code for the main crate
    │       └── ui -- UI related code
    ├── digilogic_core -- The core data types, used by most crates
    │   └── src
    ├── digilogic_gsim -- The simulation engine
    │   └── src
    ├── digilogic_layout -- Automatic layout code, mainly used when importing verilog
    │   └── src
    ├── digilogic_netcode -- The netcode connecting the simulation server and UI
    │   └── src
    ├── digilogic_routing -- Automatic wire routing code
    │   └── src
    ├── digilogic_serde -- Import / Export code for Digital and Yosys (Verilog)
    │   ├── src
    │   │   ├── digital
    │   │   ├── json
    │   │   └── yosys
    │   └── testdata
    └── digilogic_ux -- The UX (User eXperience) code -- sits between ui and core
        └── src

Again, more information can be found in the docs folder if you want to learn more.

Credits

The vast majority of the code in this repo is written by Mathis Rech, especially the simulation engine and auto-router.

I (rj45) mainly wrote the import code, UX code, and did lots of project management / design type stuff.

License

Apache 2.0, see LICENSE.