Retrocomputing with Clash
Retrocomputing with Clash
Haskell for FPGA Hardware Design
About the Book
Please visit https://retrocla.sh/ for sample chapters, print version, and links to the code repositories.
Haskell has become the functional programming language of choice for many developers due to its excellent tools for abstraction and principled program design. The open source Clash hardware description language unlocks these features for FPGA design as well.
Retrocompuing with Clash takes the experienced Haskell programmer on a journey into the world of hardware design with Clash. Our approach is based on using Haskell to its fullest potential, using abstractions like monads and lenses in building a library of reusable components.
But that wouldn't put the fun in functional programming! And so we put these components to good use in implementing various retro-computing devices:
- A desktop calculator
- A simple, but Turing-complete computer that uses Brainfuck as its machine code
- An implementation of the CHIP-8 virtual computer specification
- An Intel 8080 CPU
- Space Invaders arcade machine
- Compucolor II, a home computer from 1977 complete with keyboard, color video, and a floppy drive
I absolutely love the very Haskell approach to circuit design in this book, as opposed to my own write-Verilog-in-Haskell style. It leverages Haskell's type system in a very natural way to protect against many traps we as circuit designers often fall into.
The book clearly demonstrates the benefits of using a modern programming language for circuit design, where it builds reusable functionality and components at a far finer granularity than what I'm used to in traditional hardware description languages.
Another thing that's absolutely great is the book's use of SDL2 multimedia library to emulate peripherals like monitors which enables you to fully interact with the computers and games that you'll be building without having to go through the sometimes long and painful process of programming an FPGA.
– Christiaan Baaij, Clash lead developer, QBayLogic co-founder
This is the book for functional programmers looking to get into FPGAs and digital logic design. Learn Clash, the "I can’t believe it’s not Haskell!'" hardware description language, while indulging in nostalgia for the 1980s. Take a joyride through a variety of hands-on projects, including Pong, Space Invaders, and the Compucolor II, a personal computer based on the Intel 8080. Recommended.
– Miëtek Bak
Christiaan Baaij, Clash lead developer, QBayLogic co-founder
I absolutely love the very Haskell approach to circuit design in this book, as opposed to my own Verilog-in-Haskell style. It leverages Haskell's type system in a very natural way to protect against many traps we as circuit designers often fall into. The book clearly demonstrates the benefits of using a modern programming language for circuit design, where it builds reusable functionality and components at a far finer granularity than what I'm used to in traditional hardware description language
Miëtek Bak, mathematician
This is THE book for functional programmers looking to get into FPGAs and digital logic design. Learn Clash, the "I can’t believe it's not Haskell!" hardware description language, while indulging in nostalgia for the 1980s. Take a joyride through a variety of hands-on projects, including Pong, Space Invaders, and the Compucolor II, a personal computer based on the Intel 8080. Recommended.
Tristan de Cacqueray, principal software developer
This book is a fascinating, knowledge-expanding work that leads to exciting domains. It is hard for me to believe that I can learn about low level designs through Haskell because it is a notoriously high-level language. This language has been such a gift that has kept on giving. Thanks to the clash-shake tool, I can run Haskell code on real hardware without prior knowledge of the FPGA toolchain.
Table of Contents
- 1.1 Preliminaries
- 1.2 Notation
- 1.3 Resources
- 1.4 Acknowledgements
2 Into the world of FPGAs
- 2.1 Computers everywhere
- 2.2 Field-programmable Gate Arrays
- 2.3 Retrocomputing
- 2.4 Haskell meets Hardware
3 Hello, Clash!
- 3.3 Our first circuit
- 3.4 Summary
4 Combinational Circuits are Applicative Functors
Signalis an applicative functor
- 4.3 Controlling many LEDs
- 4.4 Seven-segment display
- 4.5 Summary
5 State, Sequencing and Clocks: The Register Transfer-Level Model
- 5.1 Clocks and registers
5.2 The RTL model:
registerand delayed feedback
- 5.3 Finally blinkenlights!
- 5.4 Passing around Clock, Reset and Enable lines implicitly
- 5.5 Multiple clocks
- 5.6 Pushbutton-toggled LED
- 5.7 Summary
6 Time-domain Multiplexing
6.1 Does this have anything to do with
- 6.2 Seven-segment displays, revisited
- 6.3 Keyboard matrix sweeping
- 6.4 Showing keypad input on a seven-segment output
- 6.5 Summary
- 6.1 Does this have anything to do with
7 Project: Pocket Calculator
- 7.1 A Minimal Viable Calculator
- 7.2 Binary Coded Decimal arithmetic
- 7.3 State and state transitions
- 7.4 An interactive software implementation
- 7.5 Hooking it up to hardware peripherals
- 7.6 Summary
8 Video Output Using VGA
- 8.1 Basic operation of a CRT display
- 8.2 Video Graphics Array
- 8.3 VGA from Clash
- 8.4 Summary
9 Generative Graphics
- 9.1 Combinational patterns
- 9.2 Stateful pattern generators
- 9.3 Animation
- 9.4 Coordinate transformations
- 9.5 Animation, differently
- 9.6 High-level simulation with SDL2
- 9.7 Summary
10 Project: Pong
- 10.1 What is Pong?
- 10.2 Top-level design
- 10.3 What is our state?
- 10.4 Drawing
- 10.5 Summary
11 Asynchronous Serial Communication
- 11.1 Synchronicity
- 11.2 Universal Asynchronous Serial Communication
- 11.3 Serial Transmitter
- 11.4 Serial Receiver
- 11.5 Applications
- 11.6 Summary
12 Programmable Machines
- 12.1 RAM machines
- 12.2 Memory
- 12.3 CPU
- 12.4 Summary
- 13.1 Why Brainfuck
- 13.2 Brainfuck as a programming language
- 13.3 Brainfuck as byte code
- 13.4 Brainfuck with external memory
- 13.5 A complete Brainfuck computer
- 13.6 Brainfuck as machine code
- 13.7 High-level simulation of the CPU
- 13.8 The logic board
- 13.9 Low-level simulation of the logic board
- 13.10 Top-level circuit and peripherals
- 13.11 Summary
- 14.1 History
- 14.2 The CHIP-8 computer
- 14.3 Instruction set
- 14.4 Video
- 14.5 CPU
- 14.6 Simulation, take 1
- 14.7 The complete machine
- 14.8 Simulation, take 2
- 14.9 Memory contention
- 14.10 Summary
15 Address decoding and memory maps
- 15.1 Room for improvement
- 15.2 A whirlwind intro to Template Haskell
- 15.3 A memory map DSL
- 15.4 Backpane connections
- 15.5 Access contention
- 15.6 Summary
16 Intel 8080
- 16.1 History
- 16.2 Veracity
- 16.3 Interface
- 16.4 Instruction set architecture
- 16.5 Instruction decoding
- 16.6 Microcoded implementation
- 16.7 Micro-architecture & micro-instructions
- 16.8 A direct software implementation
- 16.9 The complete CPU
- 16.10 Summary
17 Project: Tiny BASIC
- 17.1 What is Tiny BASIC?
- 17.2 Asynchronous Communications Interface Adapter
- 17.3 The core logic board
- 17.4 Version 1: serial I/O
- 17.5 PS/2 keyboard interface
- 17.6 Textual video
- 17.7 Screen editing
- 17.8 Version 2: Keyboard and video
- 17.9 Summary
18 Space Invaders
- 18.1 The design of Space Invaders
- 18.2 How it fits together
- 18.3 Peripherals
- 18.4 Video
- 18.5 Logic board
- 18.6 Simulation
- 18.7 Summary
19 Compucolor II
- 19.1 Design
- 19.2 A Minimal Viable Compucolor II
- 19.3 Detailed rendering with SDL
- 19.4 Video hardware
- 19.5 TMS 5501
- 19.6 Keyboard
- 19.7 Floppy drive
- 19.8 Cycle-count accuracy
- 19.9 Slowing down the CPU
- 19.10 Our complete computer
- 19.11 Summary
- 20 Parting words
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