nextpnr -- a portable FPGA place and route tool

nextpnr aims to be a vendor neutral, timing driven, FOSS FPGA place and route tool.

Currently nextpnr supports:

• Lattice iCE40 devices supported by Project IceStorm
• (experimental) Lattice ECP5 devices supported by Project Trellis
• (experimental) a "generic" back-end for user-defined architectures

We hope to see Xilinx 7 Series thanks to Project X-Ray and even more FPGA families supported in the future. We would love your help in developing this awesome new project!

Here is a screenshot of nextpnr for iCE40. Build instructions and getting started notes can be found below.

See also:

• F.A.Q.
• Architecture API

Prerequisites

The following packages need to be installed for building nextpnr, independent of the selected architecture:

• CMake 3.3 or later
• Modern C++11 compiler (clang-format required for development)
• Qt5 or later (qt5-default for Ubuntu 16.04)
• Python 3.5 or later, including development libraries (python3-dev for Ubuntu)
  • on Windows make sure to install same version as supported by vcpkg
• Boost libraries (libboost-dev or libboost-all-dev for Ubuntu)
• Latest git Yosys is required to synthesise the demo design
• For building on Windows with MSVC, usage of vcpkg is advised for dependency installation.
  • For 32 bit builds: vcpkg install boost-filesystem boost-program-options boost-thread boost-python qt5-base
  • For 64 bit builds: vcpkg install boost-filesystem:x64-windows boost-program-options:x64-windows boost-thread:x64-windows boost-python:x64-windows qt5-base:x64-windows
• For building on macOS, brew utility is needed.
  • Install all needed packages brew install cmake python boost boost-python3 qt5
  • Do not forget to add qt5 in path as well echo 'export PATH="/usr/local/opt/qt/bin:$PATH"' >> ~/.bash_profile

Getting started

nextpnr-ice40

To build the iCE40 version of nextpnr, install icestorm with chipdbs installed in /usr/local/share/icebox. Then build and install nextpnr-ice40 using the following commands:

cmake -DARCH=ice40 .
make -j$(nproc)
sudo make install

A simple example that runs on the iCEstick dev board can be found in ice40/blinky.*. Usage example:

cd ice40
yosys -p 'synth_ice40 -top blinky -json blinky.json' blinky.v               # synthesize into blinky.json
nextpnr-ice40 --hx1k --json blinky.json --pcf blinky.pcf --asc blinky.asc   # run place and route
icepack blinky.asc blinky.bin                                               # generate binary bitstream file
iceprog blinky.bin                                                          # upload design to iCEstick

Running nextpnr in GUI mode:

nextpnr-ice40 --json blinky.json --pcf blinky.pcf --asc blinky.asc --gui

(Use the toolbar buttons or the Python command console to perform actions such as pack, place, route, and write output files.)

nextpnr-ecp5

For ECP5 support, you must download Project Trellis, then follow its instructions to download the latest database and build libtrellis.

cmake -DARCH=ecp5 -DTRELLIS_ROOT=/path/to/prjtrellis .
make -j$(nproc)
sudo make install

• For an ECP5 blinky on the 45k ULX3S board, first synthesise using yosys blinky.ys in ecp5/synth.

• Then run ECP5 place-and route using ./nextpnr-ecp5 --json ecp5/synth/blinky.json --basecfg ecp5/synth/ulx3s_empty.config --textcfg ecp5/synth/ulx3s_out.config

• Create a bitstream using ecppack ulx3s_out.config ulx3s.bit

• Note that ulx3s_empty.config contains fixed/unknown bits to be copied to the output bitstream

• More examples of the ECP5 flow for a range of boards can be found in the Project Trellis Examples.

• Currently the ECP5 flow supports LUTs, flipflops and IO. IO must be instantiated using TRELLIS_IO primitives and constraints specified using LOC and IO_TYPE attributes on those instances, as is used in the examples.

nextpnr-generic

The generic target allows running placement and routing for arbitrary custom architectures.

cmake -DARCH=generic .
make -j$(nproc)
sudo make install

TBD: Getting started example for generic target.

Additional notes for building nextpnr

Use cmake -D options to specify which version of nextpnr you want to build.

Use -DARCH=... to set the architecture. It is semicolon separated list. Use cmake . -DARCH=all to build all supported architectures.

The following runs a debug build of the iCE40 architecture without GUI and without Python support and only HX1K support:

cmake -DARCH=ice40 -DCMAKE_BUILD_TYPE=Debug -DBUILD_PYTHON=OFF -DBUILD_GUI=OFF -DICE40_HX1K_ONLY=1 .
make -j$(nproc)

Notes for developers

• All code is formatted using clang-format according to the style rules in .clang-format (LLVM based with increased indent widths and brace wraps after classes).
• To automatically format all source code, run make clangformat.
• See the wiki for additional documentation on the architecture API.

Testing

• To build test binaries as well, use -DBUILD_TESTS=ON and after make run make tests to run them, or you can run separate binaries.
• To use code sanitizers use the cmake options:
  • -DSANITIZE_ADDRESS=ON
  • -DSANITIZE_MEMORY=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
  • -DSANITIZE_THREAD=ON
  • -DSANITIZE_UNDEFINED=ON
• Running valgrind example valgrind --leak-check=yes --tool=memcheck ./nextpnr-ice40 --json ice40/blinky.json

Links and references

Synthesis, simulation, and logic optimization

• Yosys
• Icarus Verilog
• ABC

FPGA bitstream documentation (and tools) projects

• Project IceStorm (Lattice iCE40)
• Project Trellis (Lattice ECP5)
• Project X-Ray (Xilinx 7-Series)
• Project Chibi (Intel MAX-V)

Other FOSS FPGA place and route projects

• Arachne PNR
• VPR/VTR
• SymbiFlow
• Gaffe
• KinglerPAR