Using the iCEBreaker with an Open Source FPGA toolchain on OS X



When I used FPGAs in the past, e.g. for my LED Display, I was using Xilinx FPGAs with their proprietary software which unfortunately runs only under Windows or Linux. This was very inconvenient and in addition the software was slow as hell.

Fortunately a new era has begun: Open-Source FPGA toolchains! It was started some time back by Clifford Wolf, who first wrote a synthesis tool called Yosys and later reverse-engineered the bitstream format for Lattice iCE-40 FPGAs. Recently a new place-and-route tool called nextpnr was developed as well. Clifford has given several talks about those tools at various events which are worth watching:

At 35C3 @esden gave several workshops explaining this toolchain using the iCEBreaker board. Although I didn't have the fortune to attend one of this workshops I had the chance to chat with @esden and he was kind enough to give me an iCEBreaker to play with.

Installing all the tools on OS X in a non-invasive way was a little bit tricky and therefor I created some homebrew recipes for easy usage. To get started with the Open Source FPGA Toolchain and the iCEBreaker board you need to follow the following steps:

  1. Tap my homebrew recipes using
    brew tap twam/openfpga
  2. Install yosys using
    brew install yosys
  3. Install icestorm using
    brew install icestorm
  4. Install nextpnr using
    brew install nextpnr --without-gui --without-arch-ecp5

    You can also install nextpnr with GUI and the additional ECP5 architecture, but this takes much longer and is not required for the iCEBreaker

  5. Clone the iCEBreaker examples using
    git clone
  6. Go to your favorite example, e.g. using
    cd icebreaker-examples/blink_count_shift
  7. Build the example using
  8. Connect your iCEBreaker via USB and run the example using
    make prog

10 thoughts on “Using the iCEBreaker with an Open Source FPGA toolchain on OS X

  1. Many thanks for the brew formula for nextpnr on OSX!

    May I suggest two more options? --no-python to exclude python scripting support and --with-static to do a build with the Boost libs statically linked.

    class Nextpnr :build
    depends_on "ninja" => :build

    depends_on "boost"
    depends_on "boost-python3"
    depends_on "eigen"
    depends_on "icestorm" if build.with? "arch-ice40"
    depends_on "prjtrellis" if build.with? "arch-ecp5"
    depends_on "python"
    depends_on "qt" if build.with? "gui"

    def install
    args = []
    args << "-DBUILD_GUI=OFF" if build.without? "gui"
    args << "-DBUILD_PYTHON=OFF" if build.without? "python"
    args << "-DSTATIC_BUILD=ON" if build.with? "static"

    archs = []
    archs << "ice40" if build.with? "arch-ice40"
    archs << "ecp5" if build.with? "arch-ecp5"
    archs << "generic" if build.with? "arch-generic"
    args << ("-DARCH=" << archs.join(";"))

    system "cmake", *args, ".", "-GNinja", *std_cmake_args
    system "ninja"
    system "ninja", "install"

    test do
    system "#{bin}/nextpnr-ecp5", "--help" if build.with? "arch-ecp5"
    system "#{bin}/nextpnr-ice40", "--help" if build.with? "arch-ice40"

  2. I can follow all steps until the build of nextPNR.
    Until we get to :
    Then I get an error seemingly a missing or misplaced dependancy.

    -- Found PythonInterp: /usr/local/opt/python/bin/python3 (found suitable version "3.7.6", minimum required is "3.5")
    CMake Error at /usr/local/Cellar/cmake/3.16.2/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
    Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS)

    I am unsure if this is a matter of moving or linking the correct directory. I am new to the world of opensource toolchains for FPGAs and terminal thrashing as well. Hope to get a simple demo up and running free from the use of IceStudio. Any help is greatly appreciated.

    • I was able to resolve this issue by taking the advice of the above comment by PNR. All issues were resolved by excluding the python scripting support using --without-python. Thank you for the clear and concise guidance.

  3. Thanks for the brew formulas! I was trying to install from source but ran into a problem linking to libtbb. I was looking for info on that error when I found your page.

    I installed nextpnr with "brew install nextpnr" (i.e. without the --without-gui option) to try the GUI. The install completed without any errors, but the resulting executable for nextpnr-ice40 complains that --gui is an unrecognized option. Note, it did install qt 6.0.3_2.

    Do you have any ideas what I should try to get the nextpnr gui?

  4. I tried reinstalling with an explicit option:

    brew reinstall nextpnr --with-gui

    but that resulted in the following build messages:

    ==> Reinstalling twam/openfpga/nextpnr --without-gui
    ==> cmake -DBUILD_GUI=OFF -DICESTORM_INSTALL_PREFIX=/usr/local/opt/icestorm -DTR
    ==> ninja

    So I reinstalled again with no options since I want the gui and the ECP5 support:

    brew reinstall nextpnr

    and I got the same build messages regarding the GUI

    ==> Reinstalling twam/openfpga/nextpnr --without-gui
    ==> ninja

    So how do I tell the formula to build with gui support?

    • Looks like nextpnr changed their options for enabling the gui. I fixed the package. You should be able to install it with

      brew install nextpnr --with-gui


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