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# Installation

Chisel is a Scala library and compiler plugin.

## Quickstart with Scala CLI​

The easiest way to use Chisel is to:

1. First, install Scala CLI.

2. Then, download the Chisel Scala CLI example.

This is easiest on the command-line (works on Linux, MacOS, and Windows Subsystem for Linux (WSL)):

    curl -O -L https://github.com/chipsalliance/chisel/releases/latest/download/chisel-example.scala

Alternatively you can download the example directly from this link.

3. Finally, use Scala CLI to compile and run the example:

    scala-cli chisel-example.scala

The Chisel Scala CLI example is a simple, single-file example of Chisel that emits Verilog to the screen.

tip

While more complex projects often use a build tool like SBT or Mill as described below, we still highly recommend using Scala CLI with the example linked above for experimentation and writing small snippets to share with others.

## Dependencies​

As described above, Scala CLI is a great "batteries included" way to use Chisel. It will automatically download and manage all dependencies of Chisel including a Java Development Kit (JDK). More complex projects will require the user to install a JDK and a build tool.

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Note that each of these dependencies are projects with their own installation instructions. Please treat the commands below as suggestions and not directives.

### Java Development Kit (JDK)​

Scala runs on the Java Virtual Machine (JVM), so it is necessary to install a JDK to use Chisel. Chisel works on any version of Java version 8 or newer; however, we recommend using an LTS release version 17 or newer. Note that Scala CLI requires Java 17 or newer so unless your system installation of Java is at least version 17, Scala CLI will download Java 17 for its own use.

You can install any distribution of the JDK you prefer. Eclipse Adoptium Temurin is a good option with support for all platforms: https://adoptium.net/installation

#### Ubuntu​

Note that Temurin is not part of the default apt repositories, so you will need to add the Eclipse Adoptium repository.

Taken from the official Temurin docs. Please note that installation on most systems will require superuser priviledges (`sudo`). You may need to prefix these commands with `sudo` including the `tee` commands following any pipes (`|`).

    # Ensure the necessary packages are present:
    apt install -y wget gpg apt-transport-https

    # Download the Eclipse Adoptium GPG key:
    wget -qO - https://packages.adoptium.net/artifactory/api/gpg/key/public | gpg --dearmor | tee /etc/apt/trusted.gpg.d/adoptium.gpg > /dev/null

    # Configure the Eclipse Adoptium apt repository
    echo "deb https://packages.adoptium.net/artifactory/deb $(awk -F= '/^VERSION_CODENAME/{print$2}' /etc/os-release) main" | tee /etc/apt/sources.list.d/adoptium.list

    # Update the apt packages
    apt update

    # Install
    apt install temurin-17-jdk

#### MacOS​

Using MacPorts:

    sudo port install openjdk17-temurin

Using Homebrew:

    brew tap homebrew/cask-versions
    brew install --cask temurin17

#### Windows​

Using Scoop:

    scoop install temurin17-jdk

Windows users may also prefer using an installer.

### Build Tools​

Scala CLI is only intended for projects made up of a single to a handful of files. Larger projects need a build tool.

#### Mill​

Mill is a modern Scala build tool with simple syntax and a better command-line experience than SBT. We recommend Chisel users use Mill.

For detailed instructions, please see the Mill documentation.

##### Linux and MacOS​

The easiest way to use Mill is with the Mill Wrapper Script `millw`:

    curl -L https://raw.githubusercontent.com/lefou/millw/0.4.11/millw > mill && chmod +x mill

You can then move this script to a global install location:

    sudo mv mill /usr/local/bin/

##### Windows​

Using Scoop:

    scoop install mill

Download `millw.bat`: https://raw.githubusercontent.com/lefou/millw/0.4.11/millw.bat.

#### SBT​

SBT is the more traditional Scala build tool with many resources and examples. It is most productively used with its REPL rather than on the command line.

##### Linux​

The easiest way to install SBT is manually from the release tarball. Note that MacOS and Windows users can also do a manual install.

    curl -s -L https://github.com/sbt/sbt/releases/download/v1.9.7/sbt-1.9.7.tgz | tar xvz

Then copy the `sbt` bootstrap script into a global install location.

    sudo mv sbt/bin/sbt /usr/local/bin/

##### MacOS​

Using MacPorts:

    sudo port install sbt

Using Homebrew:

    brew install sbt

warning

Note that `brew` installs the latest version of Java as a dependency of `sbt` even though that version of Java is not actually supported by SBT. Users are advised to remove the `brew` version of Java with the following command:

    brew uninstall --ignore-dependencies java

##### Windows​

Using Scoop:

    scoop install sbt

### Firtool​

Beginning with version 6.0, Chisel will manage the version of firtool on most systems. However, some systems (e.g. NixOS or older Linux distributions like CentOS 6) may need to build firtool from source. If you need to build firtool from source, please see the Github repository.

To override the Chisel-managed version of firtool, set environment variable `CHISEL_FIRTOOL_PATH` to point to the directory containing your firtool binary.

To see what version of firtool is recommended for a given version of Chisel, see Versioning. You can also query this information programmatically in Scala via `chisel3.BuildInfo.firtoolVersion`. For example, you can use Scala CLI to compile a tiny program on the command-line to print out this value:

    scala-cli -S 2.13 -e 'println(chisel3.BuildInfo.firtoolVersion)' --dep org.chipsalliance::chisel:6.0.0

### Verilog Simulation​

#### Verilator​

Verilator is a high-performance, open-source Verilog simulator. It is not a simulator in the traditional sense, but rather it works by transpiling your Verilog code to C++ which you then compile into a binary. This results in Verilator itself having additional requirements, like a C++ compiler supporting at least C++14, and Make.

Please see Verilator's install page for more detailed instructions.

##### Linux​

Most Linux package managers include Verilator, for example:

    apt install -y verilator

Note that the default version is likely to be old, especially on older Linux distributions. Users are encouraged to build Verilator from source, please see the instructions on the Verilator website.

##### MacOS​

Using MacPorts:

    sudo port install verilator

Using Homebrew:

    brew install verilator

##### Windows​

As mentioned above, Verilator is not a "single-executable" solution; it requires a C++ compiler and also uses quite a bit of Perl scripts. We recommend using the Yosys OSS CAD Suite build for Windows, see the install instructions. Note that the Yosys OSS CAD Suite requires MinGW (Minimalist GNU for Windows).

Any Windows users who would like to help improve this usability of Chisel on Windows are encouraged to reach out. See how to get in contact on the Chisel community page.