rstb

The rstb - Rust Test Bench - library aims to provide an easy to use Rust interface to HDL simulators which implement a VPI or VHPI interface.

It is heavily inspired by, the awesome and feature rich cocotb which uses Python to the same purpose.

So why bother? Turns out Rust is ideally suited for this task. It

• interfaces easily with C,
• since end of 2019, it supports zero-cost futures with async/await syntax, which makes writing testbenches very "ergonomic" and easy to reason about,
• has an extensive and fast growing ecosysem of open source packages,
• and on top is a blazingly fast compiled language with no runtime required.

When comparing to Python, tests in Rust are more verbose and writing them is a bit more of a hassle because of the static typing and borrow checking, but test execution is a lot faster (~80x speedup with simple D-Flipflop example).

Current features

• Scheduling simulation callbacks through awaitable abstraction objects (Triggers)
• Runtime to manage scheduling, forking, joining and cancelling of concurrent tasks
• Traversing simulation object hierarchy
• Getting and setting simulation object values
• Forcing / releasing signal values
• Macro for easily embedding user level tests
• Means to pass/fail a test
• Joining multiple tasks
• Concurrent assertions built on top of the base library incl. signal history lookup
• JUnit XML output for CI
• a nicer way to start tests from command line -> Check out rstbrun (GitHub)

Feature roadmap

• add support for real types.
• vector slices and arrays
• documentation
• a logging solution and some fancy output formatting
• Work on VHPI (No simulator I have access to supports it)
• Support more Simulators
• ...

Not on the roadmap

• Windows (although it shouldn't be a big issue)
• Mentor/Siemens Foreign Language interface

Rstb works with

• Questa/ModelSim
• Icarus Verilog
• Cadence simulators

creating a Rstb test

• Write test (see examples in this project)
• compile as C compatible dynamic library by adding crate-type = ["cdylib"] to Cargo.toml as with the examples using cargo build --release.
• Run with your favorite simulator (see run_questa.sh/run_icarus.sh/run_cadence.sh)

Run it on gitpod (using Icarus Verilog): https://gitpod.io/#https://github.com/benbr8/rstb_examples