Writing Hardware in Haskell

In this hands-on session, we will write Haskell programs, compile them into digital circuits, and flash them onto an FPGA (field programmable gate array).

FPGAs are computer chips containing logic and memory cells that can be dynamically reconfigured to implement various digital circuits. This allows to iteratively develop processors, highly parallel high-performance computations, networking stacks and more without having to manufacture a custom chip.

While traditional hardware description languages (HDLs), exist to design these systems, circuit semantics are also nicely captured by purely functional programs. Clash in particular, can compile a subset of Haskell into traditional HDLs, providing powerful high-level abstractions and correctness guarantees. It also allows reusing large parts of the existing Haskell tooling and library ecosystem.

We will start with an overview of digital circuits and FPGAs, explaining the flexibility and restrictions faced when designing hardware. After a quick demo of how to work with Clash, participants will write their own designs, test them in GHCi and compile them to hardware.

The tutorial assumes basic proficiency with Haskell, including Functors and Applicatives. FPGAs and some additional hardware are provided, but a laptop is required to run Clash and an open source hardware design toolchain.

Participants will

• gain an understanding of the inner workings of digital circuits, which they are surrounded by in their daily lives
• see examples of how to use types and common abstractions (Functor, …) to model properties of a domain
• more generally experience the versatility and expressiveness of functional programming, inspiring them to solve problems in a multitude of domains outside of what they thought is possible.

Preparation

Please prepare for the workshop by cloning this repository and following the installation instructions in the README. Doing this now will help to avoid unexpected tooling problems and allow us to start on time.

If you get stuck or something looks incorrect, please open an issue on GitHub and I will look into it as soon as possible.

Matthias Heinzel

Matthias started programming with C on microcontrollers, but during his computer engineering degree fell under the spell of immutability, purity and principled abstraction. Since then, he has been interested in both hardware, functional programming and what happens at their intersection.